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  1. 7 points
    This special COVID-19 Pandemic research topic is intended to be a resource where reputable scientific papers, reports, articles and websites are listed. New material will be continually added, so please check back frequently. Material in Green provides basic information and advice. Non-green material may contain detailed medical and scientific information which some readers may wish to avoid. Click on the title of a paper you are interested in to go straight to the full paper. If you know about other material that might be suitable, please reply to this topic with details or alternatively private message me. Our plan to rebuild: The UK Government’s COVID-19 recovery strategy Published 11th May 2020. This document describes the progress the UK has made to date in tackling the coronavirus (COVID-19) outbreak, and sets out the plans for moving to the next phase of its response to the virus. Q&A on coronaviruses (COVID-19) A Q&A by The World Health Organisation WHO). They are continuously monitoring and responding to this outbreak so this Q&A will be updated as more is known about COVID-19, how it spreads and how it is affecting people worldwide, so check back regularly. NHS advice about the coronavirus (COVID-19) NHS website containing information and advice. Stay at home: guidance for people with confirmed or possible coronavirus (COVID-19) infection Published 12 March 2020 by Public Health England. Stay at home advice (NHS) NHS website Guidance on shielding and protecting people defined on medical grounds as extremely vulnerable from COVID-19 Published 21 March 2020 by Public Health England Looking after your mental health during the Coronavirus outbreak Published 11 March 2020 by The Mental Health Foundation. COVID-19 Virus Infection and Pregnancy 2020 publication by the Royal College of Obstetricians and Gynaecologists. Contains information for pregnant women and their families. Covid-19: How long does the coronavirus last on surfaces? Published 17 Mar 2020 by BBC World. No abstract, but this is the intro: "We can pick up the Covid-19 by touching surfaces contaminated with the new coronavirus, but it is only just becoming clear how long the virus can survive outside the human body." Note: the study referred to by the BBC can be found below - Aerosol and Surface Stability. Guidance on the closure of all non-essential businesses and premises as part of further social distancing measures First published 23 March 2020 by HM Government. Claim a grant through the coronavirus (COVID-19) Self-employment Income Support Scheme Published 26 March 2020 by HM Revenue & Customs Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic? Published 2013 and written by Anna Davies University of Cambridge and Katy-Anne Thompson, Public Health England. Abstract: This study examined homemade masks as an alternative to commercial face masks. Several household materials were evaluated for the capacity to block bacterial and viral aerosols. Twenty-one healthy volunteers made their own face masks from cotton t-shirts; the masks were then tested for fit. The number of microorganisms isolated from coughs of healthy volunteers wearing their homemade mask, a surgical mask, or no mask was compared using several air-sampling techniques. The median-fit factor of the homemade masks was one-half that of the surgical masks. Both masks significantly reduced the number of microorganisms expelled by volunteers, although the surgical mask was 3 times more effective in blocking transmission than the homemade mask. Our findings suggest that a homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection. Global research on coronavirus disease (COVID-19) WHO is gathering the latest scientific findings and knowledge on COVID-19 and compiling it in a database. They update the database daily and you can download it via this link. COVID-19 Resource Centre - The Lancet To assist health workers and researchers working under challenging conditions to bring this outbreak to a close, The Lancet has created a Coronavirus Resource Centre. This resource brings together new 2019 novel coronavirus disease (COVID-19) content from across The Lancet journals as it is published. All of the COVID-19 content is free to access. The perfect virus: two gene tweaks that turned COVID-19 into a killer Published 29 March 2020. Article by Liam Mannix, The Age and Sydney Morning Herald's science reporter. No abstract but this is a fascinating article about the likely origins and emergence of the COVID-19 virus. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 Published 17 Mar 2020 by the New England Journal of Medicine. Abstract: A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic.1 We analyzed the aerosol and surface stability of SARS-CoV-2 and compared it with SARS-CoV-1, the most closely related human coronavirus. (See also the BBC article above in Green: Covid-19: How long does the coronavirus last on surfaces?) Symptom progression of COVID-19 Published 11 March 2020 by Imperial College London. Abstract: The COVID-19 epidemic was declared a Public Health Emergency of International Concern (PHEIC) by WHO on 30th January 2020 [1]. As of 8 March 2020,over107,000 cases had been reported. Here, we use published and pre-print studies of clinical characteristics of cases in mainland China as well as case studies of individuals from Hong Kong, Japan, Singapore and South Korea to examine the proportional occurrence of symptoms and the progression of symptoms through time.We find that in mainland China, where specific symptoms or disease presentation are reported, pneumonia is the most frequently mentioned, see figure 1. We found a more varied spectrum of severity in cases outside mainland China. In Hong Kong, Japan, Singapore and South Korea, fever was the most frequently reported symptom. In this latter group, presentation with pneumonia is not reported as frequently although it is more common in individuals over 60 years old.The average time from reported onset of first symptoms to the occurrence of specific symptoms or disease presentation, such as pneumonia or the use of mechanical ventilation,varied substantially. The average time to presentation with pneumonia is 5.88 days, and may be linked to testing at hospitalisation; feveris often reported at onset (where the mean time to develop fever is0.77 days). Transmissibility of 2019-nCoV Published 25 Jan 2020 by Imperial College London Abstract: Self-sustaining human-to-human transmission of the novel coronavirus COVID-19 (previously termed 2019-nCoV) is the only plausible explanation of the scale of the outbreak in Wuhan. We estimate that, on average, each case infected 2.6 (uncertainty range: 1.5-3.5) other people up to 18th January 2020, based on an analysis combining our past estimates of the size of the outbreak in Wuhan with computational modelling of potential epidemic trajectories. This implies that control measures need to block well over 60% of transmission to be effective in controlling the outbreak. It is likely, based on the experience of SARS and MERS-CoV, that the number of secondary cases caused by a case of COVID-19 is highly variable – with many cases causing no secondary infections, and a few causing many. Whether transmission is continuing at the same rate currently depends on the effectiveness of current control measures implemented in China and the extent to which the populations of affected areas have adopted risk-reducing behaviours. In the absence of antiviral drugs or vaccines, control relies upon the prompt detection and isolation of symptomatic cases. It is unclear at the current time whether this outbreak can be contained within China; uncertainties include the severity spectrum of the disease caused by this virus and whether cases with relatively mild symptoms are able to transmit the virus efficiently. Identification and testing of potential cases need to be as extensive as is permitted by healthcare and diagnostic testing capacity – including the identification, testing and isolation of suspected cases with only mild to moderate disease (e.g. influenza-like illness), when logistically feasible. Severity of 2019-novel coronavirus (nCoV) Published 10 February 2020 by Imperial College London. Abstract: We present case fatality ratio (CFR) estimates for three strata of COVID-19 (previously termed 2019-nCoV) infections. For cases detected in Hubei, we estimate the CFR to be 18% (95% credible interval: 11%-81%). For cases detected in travellers outside mainland China, we obtain central estimates of the CFR in the range 1.2-5.6% depending on the statistical methods, with substantial uncertainty around these central values. Using estimates of underlying infection prevalence in Wuhan at the end of January derived from testing of passengers on repatriation flights to Japan and Germany, we adjusted the estimates of CFR from either the early epidemic in Hubei Province, or from cases reported outside mainland China, to obtain estimates of the overall CFR in all infections (asymptomatic or symptomatic) of approximately 1% (95% confidence interval 0.5%-4%). It is important to note that the differences in these estimates does not reflect underlying differences in disease severity between countries. CFRs seen in individual countries will vary depending on the sensitivity of different surveillance systems to detect cases of differing levels of severity and the clinical care offered to severely ill cases. All CFR estimates should be viewed cautiously at the current time as the sensitivity of surveillance of both deaths and cases in mainland China is unclear. Furthermore, all estimates rely on limited data on the typical time intervals from symptom onset to death or recovery which influences the CFR estimates. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? Article published in The Lancet 11 March 2020. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020 Published 12 March 2020. Abstract: An outbreak of coronavirus disease 2019 (COVID-19) unfolded on board a Princess Cruises’ ship called the Diamond Princess. Shortly after arriving in Yokohama, Japan, this ship had been placed under quarantine orders from 5 February 2020, after a former passenger had tested positive for the virus responsible for the disease (i.e. severe acute respiratory syndrome coronavirus 2; SARS-CoV-2), subsequent to disembarking in Hong Kong. In this study, we conducted a statistical modelling analysis to estimate the proportion of asymptomatic individuals among those who tested positive for SARS-CoV-2 on board the ship until 20 February 2020 included, along with their times of infections. The model accounted for the delay in symptom onset and also for right censoring, which can occur due to the time lag between a patient’s examination and sample collection and the development of illness. Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand Published 16 March 2020 Abstract: The global impact of COVID-19 has been profound, and the public health threat it represents is the most serious seen in a respiratory virus since the 1918 H1N1 influenza pandemic.Here we present the results of epidemiological modelling which has informed policy making in the UK and other countries in recent weeks. In the absence of a COVID-19 vaccine, we assess the potential role of a number of public health measures –so-called non-pharmaceutical interventions (NPIs) –aimed at reducing contact rates in the population and thereby reducing transmission of the virus. In the results presented here, we apply a previously published micro simulation model to two countries: the UK (Great Britain specifically) and the US. We conclude that the effectiveness of any one intervention in isolation is likely to be limited, requiring multiple interventions to be combined to have a substantial impact on transmission. Report of the World Health Organisation / China Joint Mission on Coronavirus Disease 2019 (COVID-19) Published Feb 2020. No abstract. The neuroinvasive potential of SARS‐CoV2 may be at least partially responsible for the respiratory failure of COVID‐19 patients Published 20 Feb 2020. Abstract: Following the severe acute respiratory syndrome coronavirus (SARS‐CoV) and Middle East respiratory syndrome coronavirus (MERS‐CoV), another highly pathogenic coronavirus named SARS‐CoV‐2 (previously known as 2019‐nCoV) emerged in December 2019 in Wuhan, China, and rapidly spreads around the world. This virus shares highly homological sequence with SARS‐CoV, and causes acute, highly lethal pneumonia coronavirus disease 2019 (COVID‐19) with clinical symptoms similar to those reported for SARS‐CoV and MERS‐CoV. The most characteristic symptom of patients with COVID‐19 is respiratory distress, and most of the patients admitted to the intensive care could not breathe spontaneously. Additionally, some patients with COVID‐19 also showed neurologic signs, such as headache, nausea, and vomiting. Increasing evidence shows that coronaviruses are not always confined to the respiratory tract and that they may also invade the central nervous system inducing neurological diseases. The infection of SARS‐CoV has been reported in the brains from both patients and experimental animals, where the brainstem was heavily infected. Furthermore, some coronaviruses have been demonstrated able to spread via a synapse‐connected route to the medullary cardiorespiratory center from the mechanoreceptors and chemoreceptors in the lung and lower respiratory airways. In light of the high similarity between SARS‐CoV and SARS‐CoV2, it is quite likely that the potential invasion of SARS‐CoV2 is partially responsible for the acute respiratory failure of patients with COVID‐19. Awareness of this will have important guiding significance for the prevention and treatment of the SARS‐CoV‐2‐induced respiratory failure. Transplantation of ACE2- Mesenchymal Stem Cells Improves the Outcome of Patients with COVID-19 Pneumonia Published 13 March 2020. Abstract: A coronavirus (HCoV-19) has caused the novel coronavirus disease (COVID-19) outbreak in Wuhan, China. Preventing and reversing the cytokine storm may be the key to save the patients with severe COVID-19 pneumonia. Mesenchymal stem cells (MSCs) have been shown to possess a comprehensive powerful immunomodulatory function. This study aims to investigate whether MSC transplantation improves the outcome of 7 enrolled patients with COVID-19 pneumonia in Beijing YouAn Hospital, China, from Jan 23, 2020 to Feb 16, 2020. The clinical outcomes, as well as changes of inflammatory and immune function levels and adverse effects of 7 enrolled patients were assessed for 14 days after MSC injection. MSCs could cure or significantly improve the functional outcomes of seven patients without observed adverse effects. The pulmonary function and symptoms of these seven patients were significantly improved in 2 days after MSC transplantation. Among them, two common and one severe patient were recovered and discharged in 10 days after treatment. After treatment, the peripheral lymphocytes were increased, the C-reactive protein decreased, and the overactivated cytokine-secreting immune cells CXCR3+CD4+ T cells, CXCR3+CD8+ T cells, and CXCR3+ NK cells disappeared in 3-6 days. In addition, a group of CD14+CD11c+CD11bmid regulatory DC cell population dramatically increased. Meanwhile, the level of TNF-α was significantly decreased, while IL-10 increased in MSC treatment group compared to the placebo control group. Furthermore, the gene expression profile showed MSCs were ACE2- and TMPRSS2- which indicated MSCs are free from COVID-19 infection. Thus, the intravenous transplantation of MSCs was safe and effective for treatment in patients with COVID-19 pneumonia, especially for the patients in critically severe condition. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2) Published 16 March 2020. Abstract: Estimation of the prevalence and contagiousness of undocumented novel coronavirus (SARS-CoV2) infections is critical for understanding the overall prevalence and pandemic potential of this disease. Here we use observations of reported infection within China, in conjunction with mobility data, a networked dynamic metapopulation model and Bayesian inference, to infer critical epidemiological characteristics associated with SARS-CoV2, including the fraction of undocumented infections and their contagiousness. We estimate 86% of all infections were undocumented (95% CI: [82%–90%]) prior to 23 January 2020 travel restrictions. Per person, the transmission rate of undocumented infections was 55% of documented infections ([46%–62%]), yet, due to their greater numbers, undocumented infections were the infection source for 79% of documented cases. These findings explain the rapid geographic spread of SARS-CoV2 and indicate containment of this virus will be particularly challenging. Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations Published 27 March 2020 by the World Health Organisation (WHO) No abstract. The proximal origin of SARS-CoV-2 Published 17 March 2020 by Nature Medicine. Abstract: SARS-CoV-2 is the seventh coronavirus known to infect humans; SARS-CoV, MERS-CoV and SARS-CoV-2 can cause severe disease, whereas HKU1, NL63, OC43 and 229E are associated with mild symptoms6. Here we review what can be deduced about the origin of SARS-CoV-2 from comparative analysis of genomic data. We offer a perspective on the notable features of the SARS-CoV-2 genome and discuss scenarios by which they could have arisen. Our analyses clearly show that SARS-CoV-2 is not a laboratory construct or a purposefully manipulated virus. Can you kill coronavirus with UV light? Published 27th March 2020 by the BBC. Headline: There’s only one type of UV that can reliably inactivate Covid-19 – and it’s extremely dangerous. Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand Published 16th March 2020 by Imperial College London. Summary: The global impact of COVID-19 has been profound, and the public health threat it represents is the most serious seen in a respiratory virus since the 1918 H1N1 influenza pandemic. Here we present the results of epidemiological modelling which has informed policy making in the UK and other countries in recent weeks. In the absence of a COVID-19 vaccine, we assess the potential role of a number of public health measures – so-called non-pharmaceutical interventions (NPIs) – aimed at reducing contact rates in the population and thereby reducing transmission of the virus. In the results presented here, we apply a previously published micro simulation model to two countries: the UK (Great Britain specifically) and the US. We conclude that the effectiveness of any one intervention in isolation is likely to be limited, requiring multiple interventions to be combined to have a substantial impact on transmission. Two fundamental strategies are possible: (a) mitigation, which focuses on slowing but not necessarily stopping epidemic spread – reducing peak healthcare demand while protecting those most at risk of severe disease from infection, and (b) suppression, which aims to reverse epidemic growth, reducing case numbers to low levels and maintaining that situation indefinitely. Each policy has major challenges. We find that that optimal mitigation policies (combining home isolation of suspect cases, home quarantine of those living in the same household as suspect cases, and social distancing of the elderly and others at most risk of severe disease) might reduce peak healthcare demand by 2/3 and deaths by half. However, the resulting mitigated epidemic would still likely result in hundreds of thousands of deaths and health systems (most notably intensive care units) being overwhelmed many times over. For countries able to achieve it, this leaves suppression as the preferred policy option. We show that in the UK and US context, suppression will minimally require a combination of social distancing of the entire population, home isolation of cases and household quarantine of their family members. This may need to be supplemented by school and university closures, though it should be recognised that such closures may have negative impacts on health systems due to increased absenteeism. The major challenge of suppression is that this type of intensive intervention package – or something equivalently effective at reducing transmission – will need to be maintained until a vaccine becomes available (potentially 18 months or more) – given that we predict that transmission will quickly rebound if interventions are relaxed. We show that intermittent social distancing – triggered by trends in disease surveillance – may allow interventions to be relaxed temporarily in relative short time windows, but measures will need to be reintroduced if or when case numbers rebound. Last, while experience in China and now South Korea show that suppression is possible in the short term, it remains to be seen whether it is possible long-term, and whether the social and economic costs of the interventions adopted thus far can be reduced. Effectiveness of convalescent plasma therapy in severe COVID-19 patients Published 6April 2020. Abstract: Currently, there are no approved specific antiviral agents for novel coronavirus disease 2019 (COVID-19). In this study, 10 severe patients confirmed by real-time viral RNA test were enrolled prospectively. One dose of 200 mL of convalescent plasma (CP) derived from recently recovered donors with the neutralizing antibody titers above 1:640 was transfused to the patients as an addition to maximal supportive care and antiviral agents. The primary endpoint was the safety of CP transfusion. The second endpoints were the improvement of clinical symptoms and laboratory parameters within 3 d after CP transfusion. The median time from onset of illness to CP transfusion was 16.5 d. After CP transfusion, the level of neutralizing antibody increased rapidly up to 1:640 in five cases, while that of the other four cases maintained at a high level (1:640). The clinical symptoms were significantly improved along with increase of oxyhemoglobin saturation within 3 d. Several parameters tended to improve as compared to pretransfusion, including increased lymphocyte counts (0.65 × 109/L vs. 0.76 × 109/L) and decreased C-reactive protein (55.98 mg/L vs. 18.13 mg/L). Radiological examinations showed varying degrees of absorption of lung lesions within 7 d. The viral load was undetectable after transfusion in seven patients who had previous viremia. No severe adverse effects were observed. This study showed CP therapy was well tolerated and could potentially improve the clinical outcomes through neutralizing viremia in severe COVID-19 cases. The optimal dose and time point, as well as the clinical benefit of CP therapy, needs further investigation in larger well-controlled trials. A Genomic Perspective on the Origin and Emergence of SARS-CoV-2 Published 26th March 2020. Abstract: The ongoing pandemic of a new human coronavirus, SARS-CoV-2, has generated enormous global concern. We and others in China were involved in the initial genome sequencing of the virus. Herein, we describe what genomic data reveal about the emergence SARS-CoV-2 and discuss the gaps in our understanding of its origins. Temporal dynamics in viral shedding and transmissibility of COVID-19 Published 15 April 2020 Abstract: We report temporal patterns of viral shedding in 94 patients with laboratory-confirmed COVID-19 and modeled COVID-19 infectiousness profiles from a separate sample of 77 infector–infectee transmission pairs. We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home. Disease control measures should be adjusted to account for probable substantial presymptomatic transmission. First known person-to-person transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the USA Published 10th April 2020 Summary: On Jan 23, 2020, Illinois, USA, reported the state's first laboratory-confirmed case (index case) of COVID-19 in a traveller who returned from Wuhan in mid-January, 2020. Subsequently, the first evidence of secondary transmission in the USA was reported on Jan 30, when the husband of the index patient, who had not travelled outside the USA, tested positive for SARS-CoV-2. Public health authorities did an intensive epidemiological investigation of the two confirmed cases. This Article describes the first person-to-person transmission of COVID-19 in the USA, including the clinical and laboratory features of both patients and the assessment and monitoring of several hundred individuals with potential exposure to SARS-CoV-2. Classification of the cutaneous manifestations of COVID‐19: a rapid prospective nationwide consensus study in Spain with 375 cases Published 29 April 2020. Summary: Five rashes, including Covid toe, are affecting some hospital patients diagnosed with Covid-19, a small study by Spanish doctors has found. Nationwide case collection survey of images and clinical data. Using a consensus, we described 5 clinical patterns. We later described the association of these patterns with patient demographics, timing in relation to symptoms of the disease, severity, and prognosis. Lesions may be classified as acral areas of erythema with vesicles or pustules (Pseudo‐chilblain) (19%), other vesicular eruptions (9%), urticarial lesions (19%), maculopapular eruptions (47%) and livedo or necrosis (6%). Vesicular eruptions appear early in the course of the disease (15% before other symptoms). The pseudo‐chilblain pattern frequently appears late in the evolution of the COVID‐19 disease (59% after other symptoms), while the rest tend to appear with other symptoms of COVID‐19. Severity of COVID‐19 shows a gradient from less severe disease in acral lesions to most severe in the latter groups. Results are similar for confirmed and suspected cases, both in terms of clinical and epidemiological findings. Alternative diagnoses are discussed but seem unlikely for the most specific patterns (pseudo‐chilblain and vesicular). Quantifying the impact of physical distance measures on the transmission of COVID-19 in the UK Published 7th May 2020. Abstract: To mitigate and slow the spread of COVID-19, many countries have adopted unprecedented physical distancing policies, including the UK. We evaluate whether these measures might be sufficient to control the epidemic by estimating their impact on the reproduction number (R0, the average number of secondary cases generated per case). We found a 74% reduction in the average daily number of contacts observed per participant (from 10.8 to 2.8). This would be sufficient to reduce R0 from 2.6 prior to lockdown to 0.62 (95% confidence interval [CI] 0.37–0.89) after the lockdown, based on all types of contact and 0.37 (95% CI = 0.22–0.53) for physical (skin to skin) contacts only. Individual variation in susceptibility or exposure to SARS-CoV-2 lowers the herd immunity threshold Published 27th April 2020. N.B. Not peer reviewed. Abstract: As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spreads, the susceptible subpopulation is depleted causing the rate at which new cases occur to decline. Variation in individual susceptibility or exposure to infection exacerbates this effect. Individuals that are frailer, and therefore more susceptible or more exposed, have higher probabilities of being infected, depleting the susceptible subpopulation of those who are at higher risk of infection, and thus intensifying the deceleration in occurrence of new cases. Eventually, susceptible numbers become low enough to prevent epidemic growth or, in other words, herd immunity is attained. Although estimates vary, it is currently believed that herd immunity to SARS-CoV-2 requires 60-70% of the population to be immune. Here we show that variation in susceptibility or exposure to infection can reduce these estimates. Achieving accurate estimates of heterogeneity for SARS-CoV-2 is therefore of paramount importance in controlling the COVID-19 pandemic.
  2. 4 points
    A revised version of the earlier "Winter Snow Setups/Non-Snow Setups" topics, this goes through the range of winter setups we can get. As in summer, the main determining factors in what sort of winter weather we get are the positioning and strength of the jet stream. A strong jet stream means that depressions will frequently move from west to east, giving a "zonal" pattern over the UK. Because the Atlantic is relatively warm and moist, assisted by the warm North Atlantic Drift, zonal types often tend to be mild- but not always. A weak jet means lows track less frequently from west to east and blocking highs can form more readily. Whether we get cold wintry weather depends on the positioning of the high. Zonal, northerly tracking jet When low pressure systems track well to the north of Scotland, we usually end up with high pressure close by to the south, and a mild moist tropical maritime airmass covering the north. It is usually dry and mild in the south with a fair amount of sunshine, but cloudier and wetter in the north and west. Bartlett/Euro High An extension of the northerly tracking jet scenario, this setup sees the Azores High displaced over to Europe, keeping Britain in a persistent tropical maritime south-westerly regime. This setup brings Britain's warmest winter temperatures. This setup is often associated with large rainfall totals in the Scottish Highlands. Broadly speaking it tends to be dry and sunny wherever the high covers, northern and western Scotland tend to be dull and wet, and intervening areas often end up fairly dry but cloudy. Zonal, jet tracking over and to the north of Scotland This is the most common "zonal" winter pattern with low pressure systems regularly moving from west to east, bands of rain moving east at intervals, with brighter showery polar maritime air in between the rain belts. If the lows track from SW to NE then southern and eastern areas often spend a lot of time in "warm sector" mild moist tropical maritime air. It tends to be wet everywhere, sunny in the east and dull in the west. If the lows track more from NW to SE much of Britain spends a lot of time in polar maritime air, giving sunshine and showers. It tends to be wet but sunny in most regions, especially sunny in the east and especially wet in the west. On rare occasions, if there is an influx of Arctic air or cold pools from Canada/Alaska into the mid-Atlantic, we get so-called "cold zonality" with widespread snowfalls, especially in northern and western regions. An extreme case of this occurred in January 1984. Zonal, jet tracking right over Britain This pattern tends to be very wet as the lows track straight over the British Isles. Temperatures tend to be close to normal but with a bias towards milder conditions in the south, and cold polar incursions often reaching the north, giving snow for Scotland and northern England. Zonal, southerly tracking jet This pattern is not very common but when it does happen it can usher in prolonged spells of cold snowy weather for the British Isles. Low pressure stays to the south, sometimes bringing fronts into southern areas which can bring snow as the milder air meets cold polar air to the north. Otherwise, high pressure oscillates between Greenland and Scandinavia bringing repeated bursts of northerly and easterly winds. Blocked, high pressure over Britain When a winter anticyclone settles over Britain the weather tends to be dry, but the weak winter sun is ineffective at burning away low cloud. Thus sunshine amounts can vary considerably depending on how much cloud is trapped within the high- in general an input of moist tropical maritime air, or an easterly drift from the moist North Sea, may result in days on end of "anticyclonic gloom" with low cloud and mist and no chance of any sunshine. Alternatively, a clear anticyclone may bring frosty foggy nights and sunny days, as happened in December 2001 (below). Blocked, high pressure to the east When high pressure is well out to the east, this allows Atlantic lows to come towards the British Isles but they stall to the west, which tends to give rise to mild, rather cloudy southerly regimes. The equivalent of the summertime "tropical continental" southerly type which dominated the month of July 2006 rarely occurs in winter, but it does crop up occasionally. Depending on the amount of cloud circulating around the high's western periphery, a prolonged spell of anticyclonic gloom may ensue (as happened in February 1993 and early December 2004), or it may be warm and sunny by day but with cool nights, as happened in February 2008 (below). Unfortunately, with highs both over and to the east of Britain there is no synoptic way of determining how cloudy the highs will be- satellite imagery, atmospheric profiles etc. are your best bet for guidance. Blocked, strong Azores or mid-Atlantic high This kind of blocked pattern results in mostly mild weather as north-westerly winds suck up mild air from the Azores and around the high's periphery to the UK. Sometimes as a low moves out into Scandinavia it may introduce a brief burst of cold northerly or north-westerly winds with some snow showers, but these blasts usually tend to be short-lived. Blocked, Scandinavian high The Scandinavian High is often regarded as the "holy grail" by many cold/snow lovers, because it directs cold continental air across from the east. However, the Scandinavian High is really more of a building block towards an easterly- if the high is kept too far east the continental air may well stay away to the east. If an easterly does reach Britain then it will pick up moisture over the North Sea, and the resulting weather is largely dependent on the upper air temperatures, and the 850hPa temperature is often used as a guide. If the upper air is relatively mild (typically above -5C), the air will be stable and the moisture will give rise to layers of stratocumulus and persistent dull dry weather. However, if the upper air is cold (typically below -5C, preferably -10C or below) then the air will be unstable, and will give rise to heavy, often prolonged showers, especially but not exclusively for eastern areas. This setup brings much of England and Wales its coldest weather, and can produce significant snowfalls as happened in February 1991 (below). Northerly type Northerlies are another major source of snow events, brought about by high pressure to the west, and low pressure over Scandinavia or the North Sea. However, northerlies too have a major "stumbling block" if it's widespread snow you're after. Unless there is a southerly tracking jet stream, or a strong anticyclone over Greenland (preferably both), we tend to get brief "topplers" with just 36-48 hours of northerly winds, a few wintry showers for exposed coasts, and then milder weather pushes in. However, if a block can hold to our north-west for long enough for the northerly to sustain for upwards of a few days, then we will often see troughs form in the airflow bringing snow showers well inland. A large area of high pressure over Greenland, extending towards Iceland, will usually keep the British Isles affected by repeated bursts of polar air from the north. The "polar low", a low that forms in cold northerly airstreams and tracks south, is a particularly prominent source of snowfalls in a northerly regime. Although it is usually northern and eastern areas that see the most snow in a northerly regime, western areas can see the largest amount when pressure is low to the north, resulting in the Arctic air being sent south through the east Atlantic and around to Britain from the west or north-west (similar to the "cold zonality" described earlier, but via a northerly regime). Continuing the Christmas theme, this brought many western areas a white Christmas in 2004. Frontal battlegrounds Finally, when pressure is high to the north or east bringing cold polar and/or continental air towards Britain, and this cold air meets Atlantic systems coming in from the south-west, causing the systems to stall, this can lead to prolonged outbreaks of snow. For example many western areas were heavily hit during early February 1996 from this kind of setup.
  3. 3 points
    The MJO is a major contributor to the global weather patterns, so for those who want to understand a little bit more about it here is a brief overview of my current understanding of the MJO and Rossby and Kelvin Waves. First lets talk a little bit about waves or more specifically Rossby and Kelvin waves. These can occur both in the Atmosphere and in the Ocean and it is important to be clear about the difference between the two. Oceanic Rossby waves take the form of slight height changes in the sea and more apparent changes in the depth of the thermocline. These can take months or years to cross an oceanic basin and have there orrigin in anomalous atmospheric pressure patterns.In the North Pacific, for instance, a Rossby wave, after the 10 years or so that it takes to cross the basin, can push the Kuroshio Current northwards and affect weather on the North America continent. This might have happened already in 1993, the culprit Rossby wave being an effect of the 1982-83 El Niño.The important thing about oceanic rossby waves are that they are slow and westward moving. Kelvin waves move faster and eastwards taking about 70 days to cross the Pacific. See in the link below how an easterly wind anomaly at the equator can produce these waves and in the subsequent link how they are reflected to ultimately produce a pattern which has similarities to the el nino,la nina pattern. Oceanic Rossby and Kelvin wave Thory The Evolution of Oceanic Kelvin and Rossby waves The point here for me is that strong MJO events have large impacts of weather patterns and probably contribute to la nina and el nino events. We should note however that el nino and la nina tend to closely follow the volumes of warm water (20C+) at the equator so the MJO does not have it all its own way. Warm Water Volume and ENSO We recognise Rossby waves in the atmosphere as the long waves in the jetstream but there are also Kelvin waves in the atmosphere which travel eastwards around the world typically taking 40-50 days which show up as a pressure anomally. These lesser known waves may actaully play a most important role is triggering the MJO cycle. Perhaps we should just note that gravity waves are a different phenomenon and although Atmospheric Rossby waves are thought of as planetary waves I prefer to use this term for those waves in the Stratosphere, Mesosphere and Ionosphere. So onto the MJO events which have there orrigins in enhanced convection over the tropical western Pacific which create a low pressure which radiates rapidly eastward as a dry equatorial Kelvin wave over the eastern Pacific. It is blocked by the orographic barrier of the Andes and Central America for several days before propagating through the gap at Panama. After rapidly propagating as a dry equatorial Kelvin wave over the Atlantic, the sea level pressure anomaly is delayed further by the East African Highlands before it reaches the Indian Ocean and coincides with the development of enhanced convection at the start of the next MJO cycle. So we have a trigger which circulates the world over a set period (typically 50days) with one event triggering the next.Here we should note that the MJO Phases do not coincide with this circulation but reflect the eastward migration of convection once convection has been triggered. Once convection fires at the start of the cycle you will get a Rossby wave response with pressure troughs to the north and south of the area of convection. The low pressure will bring colder air in to the west of the convection killing of convection while eastward moving warm air spreads the convection eastwards. Eastwards of the low pressure systems will be strong anticyclones (high pressure) which will give strongly easterly winds at the equator. These pressure systems affect the mid latitude jetstream and hence the pattern across the north Pacific, the US and to some extent the North Atlantic and the UK. MJO Phase 2 or 3 weather pattern response MJO Phase 6 or 7 weather pattern response At the moment cool waters in the central pacific due to la nina are tending to damp down the eastward movement of convection while anomalous highs ahead of the convection will be acting to enhance la nina and slowly move it Westwards. Phase 5 through 8 of the MJO can result in a high pressure anomaly towards Alaska and a deep trough down into the central US. There are some suggestions that this high pressure towards Alaska ridges into the arctic region causing a displacement of the stratospheric vortex forcing the arctic oscillation to trend negatively. Perhaps I will revisit this when I know a bit more.
  4. 2 points
    There was already a guide written by me about UK thunderstorm set-ups, but it was done some 10+ years ago now and I've felt for a while that it needed a re-vamp and updating to make a more comprehensive guide to the processes that produce the various types of thunderstorms we see in the UK. So here it is ... the Netweather guide to thunderstorms in the British Isles .... 15 pages long: Thunderstorms in the British Isles.pdf
  5. 2 points
    This is my revised version of the summer synoptics guide. The standard summer synoptic setup Traditionally, in summer, we have a strong Azores High out to the south-west, low pressure systems moving from west to east to the north of Britain, and westerly winds dominating, bringing cool cloudy weather and rain at times. Southern areas see the warmest and sunniest weather as they are closest to the influence of ridges from the Azores High. Low pressure dominated scenarios Cool, cloudy, unsettled summer weather is often associated with a conveyor belt of strong westerly winds, a flattened Azores High well to the south-west, and low pressure systems and fronts bringing bands of rain west to east at regular intervals. The Julys of 1992, 1993, 1998, 2002 and 2004 all had this pattern. When lows track further south than usual (over northern Britain, say, rather than to the north of Scotland) it can be especially wet- July 2007 was a good example. However, if we get a significant gap in between fronts, the result tends to be a mix of sunshine and showers- the most common pattern being a sunny start, a build up of cloud towards the afternoon and then sharp showers. When we have slow moving low pressure close by and no frontal activity, such "sunshine and showers" weather can persist for days on end- this situation generally arises when the jetstream is weak. However, if the low pressure is also associated with slow moving fronts, then instead of being bright and showery it tends to be cloudy and drizzly. High pressure setups For spells of warm dry sunny weather, many look out for ridges from the Azores High extending over towards the British Isles, quietening the weather down. Sometimes this can indeed herald the start of a fine spell, if high pressure can establish over the British Isles for upwards of a few days, but more often, the ridge brings just a day or two of fine weather before the next Atlantic system comes in and the high retreats to the south-west. Often the ridge just covers southern areas, giving warm dry sunny weather in the south, and dull damp weather in the north. If a ridge from the Azores High connects with high pressure over and/or to the east of Britain, however, we may get a prolonged spell of warm dry sunny weather, for instance the famous summer of 1976 was dominated by this setup. Eastern blocking Blocking over and/or to the east of Britain can sometimes bring hot sunny spells on its own, without the need for ridging from the Azores High- such a pattern typically has low pressure to the west, and the Azores High displaced to the west of its usual position. Persistence of this pattern resulted in the hot summer of 1995 and the exceptional July of 2006. It can also give rise to significant thunderstorms when Atlantic systems push against the block, bringing a "Spanish plume" event with southerlies bringing storms up from the near Continent. However, if the jetstream strengthens, such a pattern is usually temporary, as the Atlantic systems push through, the block retreats eastwards and we get a thundery breakdown followed by westerlies. Northern blocking Sometimes high pressure prevails to the north of Britain (this type of setup is far more common during June than July or August, as the westerlies are traditionally weaker). This brings a pattern of easterly winds, it is often warm, dry and sunny in the north-west, cool, dull and misty near the east coast, while central and southern areas tend to be warm and humid with thundery rain periodically moving up from the south. The mid-Atlantic high Finally, it is also possible for the Azores High to be displaced northwards into the mid-Atlantic, giving northerlies over the British Isles. This setup tends to be cool and cloudy, especially in eastern areas, as frontal systems move southwards around the periphery of the high, though western areas are often sunny. However, if we pick up an unmodified draw of air from the Arctic with a significant gap between fronts, the result tends to be sunshine and showers- similar to what I described under the low pressure setups- this setup tends to be cool but can also provide very dramatic weather with hail and thunder, particularly for eastern England.
  6. 1 point
    Noctilucent clouds are visible in June but rare enough to cause excitement. These high ice crystal clouds can only be seen in the midsummer twilight. Once the sun comes out the light is too strong for these delicate, pale threads to be seen, they need the semi-darkness. Usually, cloud viewed in high latitudes, they were seen in mid-June 2018 in Norfolk and the Netherlands with brilliant displays over northern Britan and Northern Ireland. Read the full article here: https://www.netweather.tv/weather-forecasts/news/8977-noctilucent-clouds---night-shining-polar-mesospheric-clouds
  7. 1 point
    A quickie on the abbreviations... WZ- Wetterzentrale ( German website for viewing charts) NAO- North atlantic oscillation PNA- Pacific North american SOI./ENSO- El-Nino Southern oscillation WAA- Warm air advection CAA- Cold air advection 528 DAM- is the line drawn on the maps that equated to the temperature ( MAX) that snow can be often observed at GFS- Global forecasting sytem METO- Met office model UKMO- United kingdom Met office ECM( Or ECMWF) European centre of medium range weather forecasts.. ASL- Above sea level- PPN- Precipitation Ensembles- 10 GFS model runs- Control run is the one seen on the models SST'S sea surface temperatures PM- Polar maritime air MT- Maritime Tropical air PC- Polar Continental air LRF's - Long range forecasts MRF's- meduim range forecasts Trough- Upper level equivalent to a surface Low pressure Ridge- Upper level equivalent to a surface High pressure Blocking- The jet stream being moved AROUND CLOCKWISE a large area of high pressure. Regards Steve
  8. 1 point
    I hope the article below will help to explain what the term means and how its value is arrived at. The term DAM is used at times but its correct term is 'thickness' between the two levels in the atmosphere. Remember although its often referred to at the 1000-500mb level it can be used between any two levels. For snow forecasting the other most often used is the 1000-850mb values. DAM heights or total thickness between two levels, usually the 1000mb and 500mb I hope this may help (!) to show how complex is the relationship but also how relatively easy it is, knowing the two heights, to calculate the ‘thickness’. This can be done for any two heights. The two most referred to, usually on Net Wx to do with the will it or won’t it snow, are the 1000-500mb and the 1000-850mb heights for ‘thicknesses. Fortunately this has all been done for us by Paul and Karl with the charts shown below! DAM is what refers to the 1000-500mb thickness chart. Its rather complex but there are several ways to work out its value. Below are some of the methods which might help = height (500 hPa surface) - height (1000 hPa surface) [ for those of you, like me, too old to catch up with all the changes the world brings, millibars = hPa!, so 500 hPa is exactly the same as 500 mb. ] h(500) = h(1000)+h'(thickness). Or from that h'(thickness)=h(500)-h(1000) Thickness can be calculated from the heights reported on a radio-sonde ascent, or a thermodynamic diagram can be used to add up the partial thicknesses over successive layers to achieve the net (total) thickness. An example of the former would be 500 hPa height = 5407 m 1000 hPa height = 23 m Thickness = 5407-23 = 5384 m (or 538 dam) Careful note must be made when the height of the 1000 hPa surface is below msl thus: 500 hPa height = 5524 m 1000 hPa height = - 13 m Thickness = 5524 -(-13) = 5537 m (or 554 dam) Note the example above when surface pressure is BELOW 1000mb. Roughly it is taken that 8mb is equivalent to 6DM when forecasters are manually drawing the various upper and surface charts. If we take the actual msl and 500mb chart from GFS/Extra for 06Z this morning, see below On the left is the surface isobar chart with the 500mb height; to its right is the ‘thickness’ chart Notice the differences in values between the left and right charts-obviously the surface values are identical but NOT the ‘thickness’ and 500mb values. Or to look at how the 00z ascent for Herstmanceux differs in its 500mb height and its 500mb ‘thickness’ In the basic data format the 500mb height was given as 500.0 5490 -22.9 -50.9; i.e. 5490DM; that of the 1000mb height was 1000.0 87 8.2 5.6 The ‘thickness’ is 1000 hPa to 500 hPa thickness: 5403.00 How is that arrived at, see the formula above 100mb height is 87 500mb height is 5490 Therefore 500mb ‘thickness’=5490-87=5403DM Additional information on atmospheric thickness and it's use is available on the NOAA National Weather Service website: https://www.weather.gov/source/zhu/ZHU_Training_Page/Miscellaneous/Heights_Thicknesses/thickness_temperature.htm John Holmes
  9. 1 point
    Ok I will start a new thread for dicussions along this line and perhaps I will draw on some ideas expressed in the stratospheric thread and artic sea ice thread. I guess you would be the best person to explain all this GP but for those who don't know this thread is about global angular momentum and how it oscialltes up and down (Global Wind Oscillation) along the lines discussed by Ed Berry. Angular momentum is of course a measure of the turning force in the winds, so could perhaps be considered a measure of the strength of low pressure systems, but also relates to how much the jetstream undulates and how much blocking we have. The budget of angular momentum goes up and down as energy is lost as weather systems crash into mountains and increases as cold air meets warm. Each phase of increasing and decreasing momentum suggests different types of weather for the UK. Looking at the current GWO plot we see a liklihood of going into phases 3 and 4 based on how it usually cycles round. This implies increasing angular momentum as the various torques including mountain torque diminish (i.e those things which take energy out are not active). This is certainly true of mountain torque. For frictional torque and gravity wave torque then the jury is out. Overall it looks like global angular momentum is on the increase. The tendecy during december has been upwards. Short term I think we are looking at phases 3-4 and more of an Atlantic influence. What I am guessing at though is that low pressure systems crossing the US will increase mountain torque, equally the jet stream across india is not a weak flabby one which might increase asian mountain torque. The strong jet in the western pacific along with OLR charts suggest strong trade winds with a stationary high to the north east of Australia and convectional activity to the north west of Australia. So back to phase 1-2 fairly quickly I think afterwards. All maps are available in the link below. PSD Map room for AAM I am sure GP will tell us what he expects from the MJO and convectional activity in the pacific and how and if he expects rossby wave development as a result. It is those Rossby waves which in part will affect the stratospheric vortex and the low angular momentum could be linked to a more blocked pattern and sea ice build up to our north which I talked about in associated threads. What we should always remember though that this a complex interaction of parts of which the stratosphere plays a large part during the winter. Please note that this post and subsequent comments have been copied from the forum, so the dates/times of the comments are not correct.
  10. 1 point
    The Arctic Oscillation Arctic Oscillation is an important lead on expected winter conditions in the Northern Hemisphere, loosely described as negative ( colder ) positive ( milder). The image below gives you a great contrast of a winter we will all easily recall with an extremely negative AO and a little further back a winter at the opposite end of the scale. When considering the overall forecast for Winter it is important to note any variables which provide clues as to which end of the scale the AO will tip towards, this in turn informs us of potential for blocking episodes and also the behaviour of the jet stream. Throughout the forecast elements indicative of the mean negative AO over winter are noted. Further description The Arctic Oscillation describes simultaneous, geographically 'choreographed' shifts in multiple features of the polar vortex: air pressure, temperature, and the location and strength of the jet stream. They all follow the hemisphere-wide oscillation of atmospheric mass back and forth between the Arctic and the middle latitudes, sort of like water sloshing in a bowl. L : Positive AO R:Negative AO At one extreme of the sloshing, there is lower-than-average air pressure over the Arctic and higher-than-average pressure over the mid-latitudes. The jet stream is farther north than average under these conditions, and it steers storms northward of their usual paths. The mid-latitudes of North America, Europe, Siberia, and East Asia generally see fewer cold air outbreaks than usual. These are all characteristics of a strong, “well-behaved†polar vortex. When the atmosphere is in that state, the Arctic Oscillation Index, which tracks relative pressure anomalies across the N. Hemisphere, will have large, positive values. At the other extreme, the conditions are reversed. Air pressure is higher than average over the Arctic and lower than average over the mid-latitudes. The jet stream shifts southward of its average latitude and can develop waves or “kinks,†with “troughs†that help steer frigid, polar air southward. These are all characteristics of a weak polar vortex. When the atmosphere is in that state, the Arctic Oscillation Index will have large, negative values. Source : Climate.gov C.Kennedy, R Lindsay
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