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Nick F

Senior forecaster
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Nick F last won the day on August 21 2015

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About Nick F

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    Specialising in severe weather

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    South Norwood, London (home), Hounslow/Heathrow (work)
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    Weather - particularly thunderstorms, growing plants, walking, cycling, cooking and good food, wine.

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  1. Looks like it's turning into a horror show the 06z GFS operational run, a protracted run of long-draw mild southwesterlies and the dreaded +ve heights across mainland Europe. A glance at the extended 00z EPS 500mb mean/anomaly out day 15 doesn't offer much joy either, with low heights extending south toward the Azores which teleconnects to ridging to our south over mainland Europe right through to D15. Really need to see blues across mainland Europe, not oranges. The only positives I can draw from the morning's outputs is the medium-longer term signal for cross polar +ve heights to continue. Only problem is, for now, is the ridging is too farr away from our part of the northern hemisphere to have much influence. For now, eastern N America and eastern Siberia/Far East will be the main benefactor in terms of deep cold digging way south thanks to high latitude ridging.
  2. Convective snow showers off the North Sea with thunder snow later next week anyone? Let the 18z GFS tease you ...
  3. After several days of poor 18z runs, tonight’s is polar opposite with a cold NEly, only the GFS could make it up! Perhaps too early to throw the towel in on this particular high latitude blocking episode, but equally lots of caution required before getting hopes up for such an evolution, as a lot of complicated jigsaw pieces to fit to get to such a position as the 18z.
  4. Models making the synoptic evolution past t+144 rather complicated as they try to handle a split jet stream over the N Atlantic going around the block next week and how much energy goes into the southern arm and how much into the northern arm. Impressive Greenland block and cold air trying it's hardest to push south across the UK early next week, areas of low pressure spinning up from the SW beneath the block preventing the cold air getting all the way south in a confident manner, though the 00z EC det. does briefly at day 10 - albeit can't trust that would come off at that range. Ultimately, I think the high latitude blocking will be situated too far north for all the UK to tap into the cold air to the north, however, could be some interesting battleground snow events playing out across Scotland next week?
  5. If it was bad enough that Monday morning is looming, the 18z GFS is dishing up the horrors of wet and windy fair from the west to send us to bed on a low! Doesn’t look like it can redeem itself either, hopefully the EC will stick to its guns in the morning.
  6. The 8-14 day 500mb anomalies doesn’t show a NEly though, the coloured lines are anomalies or the deviation (+/-) in heights to the average. Then green lines are more representative of the mean flow in 8-14 day range. Still on track for some blocking over N Atlantic and Greenland area in the medium range as per ensemble and operational guidance. Longer term, the AO shows hints of recovery towards neutral indices on the chart Allseasons posted and the EPS AO and NAO forecasts likewise return to neutral indices towards the end of the month after a dip in neutral over coming 7-10 days. However, these forecasts have been chopping and changing, though there is potential for the trop PV to strengthen as we head towards late month and early Dec, the reason this could well happen is a continued forecast for an upward spike in zonal winds at 10hPa which indicates a strengthening of the stratospheric PV toward the top which would ultimately work down towards the troposphere. http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html but in the meantime, northern hemispheric flow over N Pacific, N America, N Atlantic and Europe looks like becoming rather convoluted and blocky ... so some interesting Synoptics evolving in the days ahead. Whether they produce what many are looking for, i.e. deep cold and snow, seems elusive for now, so not seeing another late Dec 2010 for now.
  7. There is always the danger that high latitude blocks will be undercut by troughing which keeps the real cold at bay from the UK, yes. Certainly it’s more unusual in November for blocks to sustain a cold pattern across the UK for long, than say in Jan or Feb when there is a greater chance because of SSWs propagating down. Exception was late November 2010 of course, though don’t think we are heading that route for now, but I still think there’s some merit in a blocked N Atlantic that will keep the UK locked into a below average spell of temps, until ECM decides to move away from this signal as well.
  8. Too early to declare a zonal rest of month and early Dec based on one GFS op run, a look at the 12z EC ensembles suggests N Atlantic blocking could be a strong possibility. There is still the chance that the trop PV will begin to organise as we head into early winter as the strat cools from top to bottom, as hinted by strengthening of zonal winds in EC forecasts on Berlin site, but for now the trop blockiness and weakish and amplified jet seems to be in control for next few weeks IMO. Below average temps more likely for a fair duration after this coming week’s milder blip, though less certainty of wintry precipitation away from the northern hills.
  9. Yes, 18z GFS with the much flatter, less amplified flow over the Atlantic, with no wave breaking of the trough over eastern Canada to help amplify the flow downstream over the N Atlantic. Still, teleconnections still seem to favour a blocked N Atlantic thanks to the weakened and convoluted jet stream over North America caused by the anomalously strong Aleutian high. 12z EPS clustering at t+240 gives strong support for mid N Atlantic blocking. So plenty to be optimistic about, despite a possibly wayward 18z GFS ... which I think is too quick to rid of the mega Aleutian block and replace it with troughing which then opens up a zonal and stronger jet to take over downstream and prevents wave breaking and blocking over N Atlantic.
  10. Next weekend could be the fourth weekend running that we have a northerly, seems reasonable ensemble support and high res consistency for it too. Quite an usual feat in recent years ... though never really potent looking for now we have to rely on it as our coldest source at the moment until out east gets colder.
  11. Remnants of Tropical Storm Rina look to cross British Isles Friday night, followed by another arctic blast from the north over the weekend. View the full blog here
  12. Said wave appears to be the remnants of now Tropical Storm Rina currently over the W Atlantic before swinging round the north side of the Azores before dropping SE across Ireland and UK Friday night/early Saturday. EC tracks it further south across SW UK and weakens it quickly. Could bring a lot of rainfall Friday night though, especially Ireland. Chart credit: wxcharts.eu: Looking at the rest of the 06z GFS op coming out, the well-advertised brief N to NWly developing late weekend could bring some snow to the Scottish mountains and tops of northern hills of England. The 500mb vortex over Greenland and Iceland re-organising and the zonal jet returning early next week to turn the flow westerly again, but still no signs of sustained re-organisation of the trop PV - it does appear that part of it will break away southeastwards into Northern Europe, while the bulk of the trop PV retreats over northern Canada - which opens up possibilities of high latitude height rises. Still plenty of promise longer term from the morning runs.
  13. Certainly continues to be encouraging signals from the models for colder blocking patterns to develop mid-late month, with no real signs of the Polar Vortex organising itself yet, a sprawling Siberian High and +ve heights over the Pole too. Early days, but the AO and NAO forecasts look similar from 00z/06z GEFS and 00z EPS with a downward / increasingly negative trend for both indices.
  14. A look at the 12z EPS clusters, 12z EPS day 10 500mb mean, the updated EC46 and the CPC Prognostic 8-14 day 500mb heights/anomalies seem to broadly point to a westerly flow regime over the coming few weeks, but with potential for some brief northerly shots in there IMO.
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