Jump to content
Will it snow? 7 day forecast Weather Radar Will it be cold?
Snow?
Local
Radar
Cold?

kold weather

Members
 View Profile  See their activity

  • Posts

    16,790

  • Joined

  • Last visited

  • Days Won

    10

 Content Type 

Blog Entries posted by kold weather

  1. kold weather
    Being we are now in Mid April I thought it was about time I did a little update on some of the major signals out there in both the Pacific and the Atlantic at the moment because they are becoming much clearer IMO.Firstly Atlantic temperatures are still at record breaking levels with March coming in 0.2C above the closest other month at 1.32C above normal, March 1969, which was a previous record for *any* month, thus March 2010 had the warmest oceans for the time of the year of any month...and April likely will be at very similar levels given there is only slight cooling signs in more SW parts of the Atlantic at the moment. I see no real sign of any fliparound of this pattern in the MDR zone as the -ve AO that caused the extreme pattern is showing real signs of re-invigorating again on the models over the next 10 days or so....Years that have featured very warm Marches/Aprils include 1958, 1969, 1998 and 2005, all had extreme seasons....The long range models are suggestive of the warmest anomalies shifting westwards, akin to what we saw in the Spring of 2005 and heled lead to the obviously extreme action we saw that year. The CFS also calls for the Gulf of Mexico to warm up greatly over the next 2-3 months reaching average and even slightly above in places by the time we get to August, and given how shallow the Gulf is that is quite plauseable even though the Gulf is still below average. Another long term factor that is becoming increasingly clear is that of the ENSO. In the last 2-3 weeks the El Nino finally has started to breakdown, with some fairly decent weekly drops now taking the EL Nino into the weak range at 0.8C, indeed daily figures are now down to 0.7C, so the weekly figure will likely drop again on the next update. Subsurface temps have really cooled off with large areas now below average and generally other factors aloft suggest the El Nino is on the way out.The models all suggest we will be in the neutral zone by June and given the current goings-on in the ENSO regions I see no reason to not agree with that. A slight westerly rebound is occuring in the trades which is usually what you see with El Ninos, which maybe suggestive of the El Nino trying one last time to sustain itself, but I suspect all it'll do is slow the drop into neutral. After June and July uncertainties begin to creep in again however either way conditions aloft will likely be condusive for an active season.It is also worth noting the ECMWF long range forecast for the summer is VERY condusive for an active season, SST's stay well above average, precip is well above normal along the main Wave train route and the model also calls for a higher then normal chance of below normal pressures, indeed the ECM is very below normal in parts of the Caribbean and W.Atlantic. All this screams hyperactive and probably a good chance of a top ten most active season since 1850.Finally, my current call is 16/9/4. I won't revise this again but as I said in another thread, I suspect my numbers have a risk of being too low, which would be quite amazing given those numbers are well above average as it is!
  2. kold weather
    A lot of talk has been going around about what the 2010 hurricane season will entail, well from my point of veiw I see many aspects that are condusive for a busy season however it is still too early to have much confidence about this season.Still here is a very brief rundown of what is emerging at the moment and what needs to be watched...1: SSTA'sThe Sea surface temperatures and thier anomalies are one of the most important factors in the hurricane season and making a call. For now they are well above normal. Interestingly something that has been noted is the SST's in the tropical E.Atlantic during Spring can give a good indication as to how busy a season will be. The E.Atlantic has become very warm which is obviously something thats sparking my interest. I'll do a sperate blog about this another time...2: Spring AO/NAOThis may not be something that you'd be thinking about but it links in very much to the first point. This is because typically a -ve NAO means a weaker Azores High and a -ve AO will mean a southerly tracking jet stream. A weaker subtropical high belt will allow for warming in the Atlantic. It is therefore hardly surprising the SST's are as warm as they are in the Atlantic, given the strength of the -ve AO/NAO this season, if we get any decent -ve bursts in the Spring, expect the SST's to challenge 2005 in the Spring...3: Sahal RainfallWhilst this is not a massivly important factor, when put in tandem with other factors it can make a difference. This is because if the Sahal region is experiencing higher rainfall its usually a good indication that conditions later in the season wil lbe condusive for systems in the tropical Atlantic.4: Tropical Stratopsheric conditionsMuch like the above, its not a massivly important factor apart from in the Autumn where the gradients between the upper air and the SST's start to increase. However it is another factor that can help out to get powerful hurricanes, and is also a more important factor for NE Atlantic systems, almost as much as SSTs.5: Position of the ITCZThis is the belt of convective acitivty that stretches across the globe. If this is further south then normal it tends to suggest there will be less convective structures in a favourable position to develop, though it can also allow more systems to get further west, and obviously vice versa.6: MJO timingsThis is a factor that is probably my weakest point, whilst this factor dosn't usually determine seasons overall activity, the MJO phase gives a very good idea about the timings of upticks of activity. This is because there tend to be dry and wet phases in the tropics, and obviously 'dry' phases will tend to surpress convective development and the other way round for the wet phase. Obviously this isn't the be all and end all and systems will still develop/not develop in both phases but it does tend to give a very good idea...of course this factor needs a very good grip on the tropics, something I'd guess GP would be well versed in!7: Pressure anomaliesThis is a very good indicator of how a season will end up evolving. This is because if you have lower then normal pressure to begin with it will be easier for a system to get going, whilst obviously it will be the other way round if you have higher then normal pressure. 2009 was an example where we had higher then normal pressure which also caused a lot of dry air in the Atlantic, whilst 2005 had well below normal pressures, esp in the Caribbean and Gulf, no surprise therefore we saw so many major hurricanes in that region that season.8: ENSO signalThis is quite probably one of the strongest signals for how a season will pan out. This is because El Nino will generally tend to cause shear in the Atlantic, esp in the Caribbean and Gulf. Neutral seasons tend to be quite active in warm phase cycle summers and La Nina's also tend to be active. It is worth noting however that in some cases a weak El nino is not a curse when it comes to activity, esp if the El nino sets up far enough west which deflects the higher shear into the E.Pacific, like we saw in 2004 and quite possibly in 1969. So these are general pointers to look out for, however what state are we in now....SST's are well above normal throughout the basin...Jan came in 3rd warmest ever and Feb maybe even higher. The gulf is cold but that is more due to the cold US winter, any prolonged period will see the SST's shot up. The general -ve NAO we've had this winter has helped to keep the SST's high as well. Typically the SST anomalies will not change greatly during Spring though obviously large scale changes will make a difference. Typically in the warm phase what you have in March in terms of anomalies tends to carry through to the summer, interestingly last year was an exception due to the big switch in ENSO states.The ECM pressure forecasts also raise my interest greatly as well. They suggest decently below normal pressure across a decent chunk of the tropical Atlantic, focused on the Caribbean region. The main reason this interests me is this is exactly what also occur in 2005, therefore needs to be watched, however of course that can all change.The big uncertainty right now is going to be the ENSO signal, typically you find active seasons become very unlikely above 0.7C however that is not a solid link. The models are quite keen to decay the El nino rapidly during the Spring, the ECM was very agressive indeed in its Feb forecast giving La Nina conditions, however I strongly suspect thats over the top in a big way and over-reacting to the big drop in late Jan.I suspect therefore we will end up between 0.3-0.7C, so borderline El nino/Neutral, however the models aren't always that great when it comes to forecasting ENSO, esp in Spring where there is a lot of change anyway occuring in the global patterns.So at the moment I'd be happy to call an above average season, from the data/forecasts I've seen, however with the added warning that a lot of these factors have time to shift and change...for example the El Nino could stay wher eit is now and not weaken much, the stratosphere temps could rocket, we could see a strong Azores high build in late spring/early summer and cause an uptick in the trades and also a big surge of dry air from Africa and also for pressure to be much higher then forecasted and before you know it your looking at a below normal season...However for now, I see nothing that is going to prevent a busy season apart from the El Nino taking longer to be gone!
  3. kold weather
    Cookie asked me a good question on the comments page about whether the 2005 season could happen again, with this question in mind I've decided to do another blog entry on this very topic, that being what did cause 2005 to be so busy?Well in my mind there are 2 main reasons, but a 3rd reason which is why this season came in above the likes of other super above average seasons such as 1933 and 1887...[b]Reason 1:[/b] Weak El nino of the 2nd half of 2004 pushed Atlantic tropical SST's even higher up then they were in the season of 2004. This was then followed by a slack Azores/Bermuda high during the spring of 2005 which allowed further warming upto record temperatures by the time we reached May. Such warm temperatures, esp in the Western Atlantic is what helped aid so many hurricanes that season in generally favourable conditions[b]Reason 2:[/b]During the summer of 2005 a rather unusual occurence occured, the Pacific monsoonal trough spread a lot further east then it usually would, getting well into the Caribbean. This meant lower then normal surface pressures for a good part of the western basin. This also meant a good breeding ground for tropical cyclones and therefore it should not be surprising that most of the storms formed west of 50-60W. Another point worth making with this reason is 3 of the top 10 deepest pressures in the basin were recorded in 2005. This is not by chance and also purely because of the monsoonal trough being present which meant pressure was lower then normal even before any system was present. Usually any monsoonal will not tend to last long before retreating back westwards but the fact it lasted for so long was unusual. It is worth noting this is why the WPAC basin tends to be so active and thats why 2005 had a similar number of storms in the Atlantic as in the Westr Pacific.[b]Reason 3:[/b]This reason is somewhat hypothetical in nature simply because I don't have the data in front of me, but here we go anyway!The NE part of the basin was very active in the Autumn of 2005 with quite a few systems that developed tropical features in parts of the Atlantic that are not typically warm enough to give tropical systems during Autumn. The above normal SST's helped but they clearly weren't the full picture...and thus what was the cause?Well to put it simply the driving force for deep convection to form in the first place is the lapse rates, the difference between the surface and the upper levels. I can only imagine that during Autumn of 2005 the uppers in this part of the world were below normal, this therefore meant surface temperatures could be that bit lower and still allow deep enough convection for the system to be tropical. However these systems are for another blog thats for sure!So those are the three reasons in my eyes, the ENSO state clearly is always going to be important but given it was a neutral season for most of it, the other three factors probably had a larger direct part in why the hurricane season of 2005 had so many storms as it did.Its worth comparing 2005 to 1933 and 1887 as well, and more to the point look at the maps and see where the storms were:1887:[url="http://weather.unisys.com/hurricane/atlantic/1887/track.gif"]http://weather.unisys.com/hurricane/atlantic/1887/track.gif[/url]1933:[url="http://weather.unisys.com/hurricane/atlantic/1933/track.gif"]http://weather.unisys.com/hurricane/atlantic/1933/track.gif[/url]2005:[url="http://weather.unisys.com/hurricane/atlantic/2005/track.gif"]http://weather.unisys.com/hurricane/atlantic/2005/track.gif[/url]The key thing to note is just how few storms there were east of 40E, indeed 1887 only had 1 whilst 1933 has none. Compare that to 2005 which had 5-7 storms. What does this mean?Possibly either 1933 or 1887 could have been every bit as active at least in terms of numbers of storms. The simple truth is we'll never know but because data was both lower in terms of quantity and sometimes quality, plus our understanding has improved loads (I'm sure there were systems in 2005 that would have been thought as just extratropical systems, esp in Autumn, afterall remember the old 26.5C rule, which is in theory not actually true) its quite possible they had as many storms as 2005 and some may have been stronger then currently estimated.So in conclusion, the 2005 was indeed an amazing season and had exceptionally positive factors which helped it be super active, however there have been other very active seasons in the last 150 years which may have been nearly as busy.
  4. kold weather
    Well here we are in the middle of this cold winter and I find myself already thinking of the hurricane season. I think most storm people, be it hurricane lovers, tornado lovers and even just bog standard convective lovers tend to get something of the winter blues at the back end of the winter and this winter seems to be no different for me, indeed if anything its even worse thanks to how good this winter has been!Anyway I did plan to do a blog way back when the blog system was first started but never found enough time to comment on it but now, in 2010 I feel I have just enough time and also dedication to go for it, very simply I'll put my thoughts about certain systems up here every now and then, esp with the biggies of course!Firstly, here is the 2010 season name list, which is quite different from the last outing of this name set in 2004, as there were several hurricanes retired from that list. So anyway here it is, with new names in red AlexBonnie[color="#ff0000"][b]Colin[/b][/color]DanielleEarl[color="#ff0000"][b]Fiona[/b][/color]GastonHermine[color="#ff0000"][b]Igor[/b][/color][color="#ff0000"][b]Julia[/b][/color]KarlLisaMatthewNicoleOttoPaulaRichardSharyTomasVirginieWalter Also one other little fact, in 1952 we would have already had our first tropical storm. A very rare system formed in the Caribbean and tracked NE making landfall in Florida. Just how tropical this sysem really was is unknown but forming on the 2nd of Feb, its the earliest pure tropical storm to form in the Atlantic basin. Indeed only 5 systems have developed before May in the Atlantic, the last being tropical storm Ana which developed in April 2003, such systems are very rare and thus are not to be expected in any season, though obviously they do crop up every now and then!Anyway I'll leave it at that for now, I'll update when I can as there may well be other systems from other basins that deserve a mention but until next time, stay safe!
  5. kold weather
    Hello everyone, this blog is where I'll be making forecast for storms when they develop in the Atlantic in the 07 season.
    This was inspired by the net-weather forecasters blogs and I thought to myself why can I not do one on hurricanes, something I do know something about, and hence why this blog page is here right now.
    We've already had subtropical storm Andrea which developed from a cold cored system that moved off from the NE then dug down SSE as a strong high pressure cell developed over Canada at 1036mbs helping to give a tight pressure gradient and allowing gusts of 55-70kts as well as giving forcing for the system to develop further. At the time it was a baroclinic low (cold cored) however as it moved over the Gulf stream, a area of flowing water which is also warmer the system started to develop shallow convection as the lapse rates grew between the surface waters and the cooler atmosphere above. As this occurs instability increases and the storms can become larger and stronger which drives pressure down eventually.
    Andrea showed such a transition. Now lets briefly qualify what a subtropical storm requires to be upgraded:
    1: A closed low level circulation. this is sometimes hard to tell in pure tropical systems but easier to tell with subtropical storms because:
    2: Convection is usually displaced a little away from the center of the low level circulation. This also means that the system has a larger wind-field, which is a tell-tale sign of a subtropical storm.
    3: Separation from the frontal system. This third requirement usually occurs though with storms that transfer from cold cored systems (baroclinic) to warm core systems (barotropic)
    Now lets see if Andrea fits the bill:

    The circulation was present based on IR and clearly the circulation is evident with the center somewhere in the red in the above visible image. The convection is displaced to the east of the center and clearly there is no frontal system visible which means the system fits into the criteria of subtropical cyclone and as winds had already been upped because of the tight gradient the previous days it meant it was upgraded to Andrea right away. As the gradient slackened and as it moved off the gulf stream it weakened with nothing to sustain it.
    While I didn't make a blog forecast on this system my call of a subtropical storm possibly and also 35-45mph max sustained winds looked a decent enough call and also made the right call in dismissing the more aggressive models which progged a hurricane.
    Next Blog should be sometime early next week, where we'll be looking at other early season storms, of course unless another system starts to develop!
    hoped you enjoyed it.
×
×
  • Create New...