Winter Weather Outlook for VA Part 2; Washout and Storms Possible Wednesday
Well first off, I haven't been blogging too much because of busy schedules homework and all. I also will admit that I have been overcommenting on master's blog so much and haven't been typing up that many blogs lately, hopefully the approaching winter will enable me to do so.
Along with posting another blog, I have officially accomplished a milestone, on my 100th post! Thanks to all who commented and contributed to my blog, especially during the busy winter.
It's getting close fellows, winter is not too far from now. That said, it's time for our winter weather outlook. First I want to start off by saying seasonal forecasting is not just a blind guess, it's about looking at the weather patterns, setups and even going by past analog winters(winters in the past with similar characteristics). The variables that do come into play when doing a winter outlook, are the ENSO(La Nina/El Nino), SSTA (Sea Surface Temperature Anomalies),snow cover in Oct-Nov in North America, QBOs, NAO, soil moisture patterns, and overall pattern in October/November. I won't cover all those, as some of those terms are difficult and quite complex, but I will cover more of the basics.
To start off, let's review last winter of 10-11. The CPC's initial forecast had normal precipitation and slightly above normal temperatures. The outcome was quite different, however, as we saw below normal temps and slightly above normal precipitation. It was deemed to be poorly forecasted.
Next, La Nina/El Nino. Last year we were under a weak/moderate La Nina. The waters in the Pacific are cooling at this point, which would indicate that we are most certainly will have a La Nina winter. This ENSO chart shows the incline and decline in SST anomalies.
Our winter would likely end up in the -0.5 to the -1 C range which isn't as deep as last winter, which suggests that this winter would be a weaker La Nina than the last. Weak La Ninas in the past, have consisted of slightly cooler than normal temperatures and normal precipitation.
Winter Weather Outlooks also are based off of who is getting what in the fall. In 10-11, the midwest was getting soaked, whereas 09-10 the wet spots were in the deep south, especially around the Mississippi Delta. It all depends on the weather pattern. If there are deep persistent troughs throughout the fall, then that pattern would likely continue through at least the first half of the winter. Steep troughs and the jet stream dips would favor coastal storms, the storms that typically bring us our big snows. So far this fall, we have had deep troughs, bringing us quite a bit of rain, so those signs point to a busy winter ahead for us. If the flow is more zonal ( west to east ) then the winter would likely be a quiet one. In 2010 the troughs were somewhat steep, but more zonal than in 09-10 and so far this fall, so therefore last winter was around or slightly above average as far as precipitation goes.
I will have more on this upcoming winter in a few hours in Part 2, along with the tropics and the forecast.
SAT NOON UPDATE
Light rain and drizzle continues to fall, with a stiff N wind. A few ice pellets have mixed in from time to time throughout the storm but overall mainly rain. There were even a few reports of flakes on the west end. None reported here in Chesterfield County. We are just about done as the storm moves up the coast and dumps a record breaking October snow to much of the Northeast. A few showers could develop with a few flakes or ice pellets mixing in as the temperature continues to drop, but overall we should be done. Areas to our west such as along I 81 have seen a little snow, about 2-3", which was their first snow of the season. I would watch though for the potential for a wraparound band. Those have caught us by surprise in the past, and I would not be shocked if one does indeed form.
WINTER WEATHER OUTLOOK PART 2
Hurricane seasons can bring us a hint of what's to come in the winter. For example, in 09-10 winter, the 09 season had only a few storms, with no east coast landfalls and plenty of recurves. Nor-Ida in Nov of 2009 set us up for the pattern for the coming winter. That was a strong El Nino, which favors little activity in the tropics and a busy winter for the east coast. Another example was last year in the 2010 hurricane season. It was active, however we saw no east coast landfalls and plenty of recurves. That and the following winter was under a moderate La Nina, however, the pattern did not favor any US impacts. Other winters like 1978-79 that were busy were quiet and had a lot of recurves. The hurricane season 2005 was very busy as we all know, and the following winter was quiet. Overall the rule of thumb is, if there are plenty of recurves in a hurricane season, then you can expect an active winter. If it's a quiet season with plenty of recurves then that can also mean an even more active winter. However if you have several US landfalls then expect a quiet winter. So far we have had 1 US East Coast landfall, which of course was Irene, however, that was forced up the coast by a trough, and it just so happened that the trough was weak and far enough inland which allowed Irene to impact NC and points up the coast. The rest of the storms consisted of recurves and Mexico storms with the exception of Lee, a TS which impacted the Gulf Coast. If we go partly by this season so far, then we can expect an active winter.
A breakdown of the weather pattern throughout the winter will consist of a cold and snowy December, , a normal January, and normal temperatures and above normal precipitation. This resembles the winter of 09-10, which brought a cold, and very snowy December, a relatively quiet January, and an active February which had 2 snowstorms 2 weekends in a row.
Overall, this winter will share the characteristics of both the 09-10 winter and last winter. 09-10 would resemble the pattern for each month, and 10-11 being a weak-moderate La Nina. The pattern so far would likely favor those big classic coastal lows along the east coast. The storm that is moving up the coast today is a great example. We will just have to see if this pattern of upper disturbances generating coastal lows will continue, only with deeper and colder air, and what the trend will be over the next month or so. If there is a very -NAO (lots of High Latitude Blocking) then it could very well be like 1995-96, the same winter of course, as the blizzard of 96 which dumped well over a foot of snow. That storm was driven by a -NAO. IF the blocking pattern doesn't hang around then the pattern would likely favor the big storms over the mid-west which is what we saw in the 2nd half of last winter. Also if you are still looking for a first flake, watch for a better chance for a first snow(if you haven't seen any) in mid-late November into early December. This winter will definitely be interesting for sure. I will have another update mid-late November.
Comments are encouraged!
NOVEMBER WINTER WX OUTLOOK UPDATE
Alright, there has been little change to the updated winter weather forecast. However, it does appear that our first real cold shot will likely not arrive until early December, so the stretch of mild temperatures should continue, albeit a few cold fronts that may allow a few frosty mornings. Chances for any winter weather over the next 2 weeks are quite slim given the pattern, but I would start watching for those first flakes at the beginning of December when we start having those arctic blasts. Snow lovers, do not panic! It is not unusual to see a mild fall and have a shift towards a colder and perhaps more wintry pattern once winter arrives. I'm not anticipating another winter like 06-07. Until then, expect temperatures to be above average and a few morning freezes.
This warm weather we have been stuck in has just been unbelievable. High temperatures have consistently topped out in the 60s and even 70s. Today we topped out in the mid 70s, the second (or third correct me if I'm wrong) 70 degree day in a row, and we will likely see another one tomorrow. That will all change, however, as a cold front sweeping from the NW will not only usher in cooler weather, but will also bring us a good bit of rain. Showers will become a little more widespread later tonight, and by tomorrow morning, expect a pouring rain for your morning commute. The rain should remain steady through the lunch hour, then should taper off. By early afternoon (2ish) the next round of rain should be moving through, and accompanying that will be a few thunderstorms. Some of the strongest could produce heavy downpours, gusty winds and occasional lightning. The SPC has put areas just to the SE of metro under a slight risk of severe weather. Damaging straight line winds, more frequent lightning, and heavy downpours will be possible there. The front should pass through as the rain begins to taper off Wednesday night, leaving behind a few showers for Thursday morning. After that, expect some clearing later on that morning. It will be a bit cooler as well following the front, as highs are expected to top out in the mid 50s. Friday morning temperatures may bottom out to freezing with highs in the mid 50s, and the same could be said about Saturday. From there on out, expect a warming trend as temperatures top out in the 60s through early next week. There is a slight chance of a few showers Sunday into Monday as a weak disturbance sweeps through the area. Models are hinting at a possible storm around Thanksgiving, but it's far out and it will likely change a thousand times before it gets here. Fingers crossed that our Thanksgiving stays dry!
Enjoy the rest of your week!