Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 3:55 PM GMT on December 30, 2008
Thoughts on December 31 storm...
A relatively organized Alberta clipper will make a swing at northern Pennsylvania with some light to moderate snow accumulations. 1004mb vortex will be dropping out of the Upper Great Lakes in Michigan spreading light snow to the north of the track with the heaviest amounts located along and to the north of the 500mb jet streak. The clipper will be fast moving and only produce snow at locations for a little over 6hours. Initially there is some dry air to overcome as dewpoints are low in the teens, but with enough forcing this afternoon by later today some light snow will break out across western Pennsylvania. With cold air aloft and at the surface for areas north of I-80 it will be easy for snow ratios near 15:1 or 20:1 with decent ice crystal growth and dendrite development. Higher elevations above 1800ft with eastern facing slopes will pick up the highest accumulations of snow as orographic lift will be able to add to the moisture content. Forcing and energy with the associated clipper is rather impressive given the typical lack of dynamics with these systems. QPF will likely max out around .4inches somewhere in the northeastern mountains. Even with .25inches of QPF across the north country, snow ratios and excellent ice crystal growth will be able to accumulate 5inches in favored locations. Looking at bufkit data, Omega levels will also be near excellent values for precipitation development across northern locations. H85s will be around -10C for a majority of the event giving all snow to all locations that recieve precipitation. Snow will also fall during the nocturnal hours favoring snow accumulations widespread despite some warmer ground surface temperatures. This will be a moderate to high impact event thanks to the amount of travelers for New Years Eve with routes impacted such as interstate 80, route 5, interstate 81, and the Pennsylvania turnpike. The majority of the precipitation will be over by early Wednesday morning. Behind the clipper will be a much colder airmass with H85s dropping to near -20C at the NY/PA border. Winds will also become gusty as clipper bombs at near 988mb and lower off of Cape Cod up through the Gulf of Maine. Lake effect snow will also develop behind the system with a 310-320 trajectory gradually becoming a due north 360 trajectory ahead of a ridge/high pressure moving in from the Midwest. A few Huron-Erie streamers could develop for a short period on Wednesday adding to snow totals across northwestern Pennsylvania and the Laurel Highlands with some spots receiving up to 4inches of pure lake effect snow. Again fluff factor will be quite high, so snow will be squeezed out of relatively low moisture content. High pressure moves in for the coldest New Years Eve in several years with temperatures in the teens and single digits under a blustery northerly wind. No timeline will be issued for this event due to the short period of impact from Tuesday evening through early Wednesday morning.
This is my current rain/snow line...
This is an Alberta Clipper with marginal cold air in place for a mostly all snow event. Freezing rain/sleet/and plain rain is not likely in most all areas that receive QPF from this event. This is an all snow event.
1. Moderate impacts due to high amount of holiday travelers.
2. Burst of snow possible during height of event.
3. Light to moderate snow accumulations.
4. Snow confined to northern Pennsylvania from I-80 north.
5. Quick event with rapidly moving shortwave.
*Note areas south of 1-3inch line may see some coatings. Also I did take in account elevation so the boundaries between accumulations are not smooth.
Selected City Accumulations for the Northeast...
Hagerstown, MD- Cold and windy with a few flurries.
Baltimore, MD- Cold and partly cloudy.
Washington, DC- Cold and partly cloudy, breezy.
Wilmington, DE- Cold and mostly cloudy with a few flurries.
Dover, DE- Cold and partly cloudy.
Cape May, NJ- Cold and cloudy with a few flurries, breezy.
Trenton, NJ- Cloudy with a trace of a few snow showers.
New York City, NY- Cloudy with light snow at times. 1-2inches of snow possible.
Poughkeepsie, NY- Light to moderate snow at times. Snow accumulations 3-6inches.
Binghamton, NY- Light to moderate snow with 3-6inches of snow.
Albany, NY- Light snow possible accumulating up to 2inches.
Hartford, CT- Moderate snow at times with 3-7inches possible.
Concord, NH- Light snow and windy. Snow accumulations 1-2inches.
Providence, RI- Moderate snow with accumulations 4-7inches.
Worcester, MA- Moderate snow possible with 4-7inches.
Boston, MA- Light to moderate snow with 3-6inches.
Nantucket, MA- Moderate snow with accumulations 3-5inches.
Hyannis, MA- Moderate to heavy snow at times. Snow accumulations 4-7inches.
Portland, ME- Light snow. Accumulations 1-2inches.
Bangor, ME- A few light snow showers with C-1inch of accumulation.
"Subject to Change"
Decent model consensus on this event, but by far the model that lead this entire track was the EURO. The EURO had a further south solution for quite a while along with showing more widespread QPF. The CMC then finally caught on with the southern solution followed lastly by the GFS. The GFS for the longest time showed a weak clipper moving across Northern New England. Then we began to slowly see a southern shift with each model run. For my forecast guidance I used the EURO track and GFS QPF shield. The EURO tracks the central vortex over the PA turnpike. All of the precipitation will fall north of the center which is being indicated. There seems to be a sharp cutoff to snow and non snow likely resulting in a few forecast busts. The NMM WRF HIRES 0z seems to have a good hold on the simulated radar for the height of the event across Pennsylvania...
Note the sharp cutoff between moderate snow and no snow positioned about 20miles north of the Pennsylvania turnpike. The short term NAM model seems to have a good hold on the track of this system across southern Pennsylvania, but there does appear to be some QPF errors in the model run likely enhancing all locations by about .1-.2inches too much. Overall seems models have a good hold on the system, but I am still noting southern shifts in each model run. I am not concerned about it, but it is just something minor to note.
After the storm...
Alright, well this is a pretty optimistic long term forecast. It appears we are entering the best period of Atlantic and Pacific correspondance for east coast storm tracks since the winter of 2002 and 2003. Now I can see this all falling apart, but I will save the scenario towards the end of the discussion. Let me first talk about the event for Friday, or should I saw what was the event Friday. For nearly a week we tracking what could have been an east coast snowstorm. We had developed a negative NAO with Greenland Blocking. But what we did not have was a favorable Pacific thanks to a very strong low plowing into the Pacific Northwest. This therefore led to the jet not digging in and phasing with the southern jet for a secondary low as the primary low heads off to the north. Placement of the 50/50 low also got a bit squashed to the north. Anyways it does not seem the linking will be made therefore the event will likely only favor a C-1inch of snow with snow showers while a low forms well off the coast barely even scraping the New England Maritimes.
Ok, now onto the more optimistic side of things. We are entering a two week pattern of very favorable teleconnections and setups. First off a negative NAO will be developing during this early to mid January time period with a high developing over Greenland. In fact during some periods the H85s will be above +0C. There has also been indications of blocking developing over the Hudson Bay and Davis Straights. The AO index has also been sharply headed negative. Now that leads to the possibility of two things. One is the cold is headed towards Asia with the lesser of the anomaly across North America. Or the coldest air heads over North America leaving Asia with a more modified airmass. It appears that the latter of the two scenarios is likely. There also appears to be a more favorable transition to a new MJO phase as we pull out of 4/5 and possibly into phase 6. Looking at January analogs this favors the cooler air stationed over the midwest and east coast. GFS operational and GFS ensembles are in good correspondance for this development along with the EURO operational and EURO ensembles. Now the question more or less turns to the Pacific. The Pacific has been in an highly unfavorable flow for us here in the east trying to get a non Great Lakes cutter of a storm. The GFS ensembles have finally come to the idea of a positive PNA development near +1 standard deviation around the 5-8th of January. But this is not set in stone by any means, as EURO and GFS have both questioned this development. One positive out of the Pacific is the momentum of the Alaskan Vortex positioning now across Canada delivering the United States colder air. Alaska has been having brutally cold air the last few days and weeks. When there is a strong Alaska anticyclone there has never been an east coast major snowstorm. The new positioning of this polar vortex will favor downstream troughing over the east coast. So then turns the question of West Coast ridging. Latest GFS/EURO 8-10 day means show beautiful ridge across the west with repositioned Polar Vortex and Hudson Bay blocking. Maps really look great, but can these models be taken seriously? They have been anything but consistent with previous events in December. The side of confidence that I am given is the wonderful agreement between all of the global models. Now what can really throw this setup off is the continued development of the cooling sea surface temperatures in the central Pacific cooling to nearly 1 deviation below normal. Yes that means a La Nina is already occuring although Climate Prediction Center is reluctant to classify it. But there is some optimism I suppose; it does not appear the affects towards the United States will not be as great as they were last year. It does not appear we will have to worry about the southeast ridge for at least the next two weeks. But down the road it may be of a concern. Also of concern is the QBO index which could inhibit ridging on west coast, but that remains to be seen. So what does that all mean for you?
Well it appears we are finally headed into a favorable storm track along the east coast. And during the winter time that means major winter storms. A pattern this favorable has not been modeled to this fullest since the winter of 02/03. There also appears to be an interesting split flow develop month which could favor the recently rare Miller A type storm that develops out of the Gulf of Mexico. Highs seem to be provided up in southern Canada to fuel the cold air with the Polar Vortex setting up over central Canada keeping the cold air continuosly funneling into the region. Blocking would develop to inhibit Great Lakes Cutters into secondary lows. But things could go completely wrong with the pattern if the Pacific does not cooperate or if the scenario does not become modeled as we get closer to the time period. The ENSO/SO could also provide issues. In any case I am looking for these as possible storm dates...
7/8... It seems that this situation is likely with a primary headed up through Great Lakes with secondary development off Carolina coast for the classic Miller B type storm. EURO/GFS have relatively similar scenarios. Blocking and a negative NAO appear to be in place but the ridging in west is a little questionable. Some places could see a significant ice storm as high should be in place in southern Canada. There is also the possibility of no secondary development putting us in the warm sector which going by the pattern of the last two/three winters; this makes this scenario quite likely.
9/10/11... This appears to hold the best potential for a pure east coast storm track and also be the third storm in the series under the blocking. Still very far out, but main concern for this event would be surpression which has been modeled by the GFS.
14/15... Another storm opportunity but yet too far out for any specifics.
In conclusion we have a great opportunity that appears to last through mid January. This too me seems to be probably the best potential to hold the largest snowstorm of season. That is not too say the other months won't be snowy, but this period has the best teleconnections modeled by the computer models in quite awhile. Still keep in mind how poorly the models have verified lately so keep hope high, but do not get overally excited, lol.
Please post storm reports in this blog from across the Northeast during the winter storm...
This blog is in progress. Check back soon...
"Here northeast of Harrisburg 2008-2009 winter statistics"
Current Snow Cover- 0.00inches
Monthly Total- 4.35inches
Seasonal Total- 10.45inches
Winter Weather Advisories- 5
Winter Storm Warnings- 0
Blizzard Warnings- 0
Ice Storm Warning- 1
Freezing Rain Advisory- 0
Winter Storm Watches- 2
Lowest High Temperature- 23
Lowest Low Temperature- 10
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First Snow - October 29 - Trace
First Snow on Ground - November 18 - Coating
Lake Effect Snow - November 21/22 - 6.00inches
Synoptic Snow - December 16 - 3.5inches
Winter Storm Discussion for January 6-7...
Surface analysis continues to show high pressure out in Indiana and moving northeastward quickly ahead of the next system. A nearly stalled frontal boundary is draped across the southeast causing its own assortment of problems. Latest radar returns show very light virga across the Middle Atlantic thanks to some warm air advection along with high moisture streaming in aloft. Clouds are beginning to thicken and will slowly lower through the night. But temperatures should be allowed to fall near freezing for many locations before coming to a halt. Then as the precipitation falls evaporational cooling with bring temperatures down into the 20s. Low pressure along stalled front will cause precipitation shield to slide to our south overnight while a new low pressure forms and sets sail towards the Great Lakes. This is a classic example why not to take teleconnections such as a negative NAO verbatum for an east coast storm track. Synoptics are much more than that. Low pressure will bring a cold front through Ohio Valley with a warm front likely located across Maryland for most of the storm. A weak anticyclone to our northeast will result in cold air damming along with some confluence from Canada. Warm air advections snows will break out by daybreak across the southern border counties already beginning to mix with sleet as H85s stay marginal near (-1C)-(-3C). Rising warm air aloft from the southwest will result in a changeover to mixed precipitation for southern areas likely by midday possibly early evening while the north then deals with a bit more snow on the order of 2-4inches. Surging PWATs a few deviations above normal will provide decent Gulf Moisture. There will likely be a weak secondary low forming along the Atlantic Coast which will only help to enhance the cold air damming. Through Tuesday night freezing rain should be ongoing across much of Pennsylvania up to about 25miles north of I-80. By Wednesday morning a dry slot should enter much of the region meanwhile as the cold air damming finally loses the battle. By Wednesday afternoon colder air will work into the region causing any leftover precipitation to turn to a trace of snow. Final accumulations of snow... Look for a widespread 1-3inches from I-80 southward with some isolated amounts near 4inches particularily in the higher elevations. Across northern Pennsylvania amounts should be more on the order of 2-5inches. Sleet accumulations look to be moderate in a few areas with some areas across the I-80 corridor receiving 1-2inches of pure sleet. Freezing rain is the main threat with this storm likely giving areas from Wisconisco to Tower City to Hazleton to Mt. Pocono a pretty destructive ice storm. But overall many areas are likely to see .25inches of freezing rain with some areas near a half an inch. Again marginal temperatures may prove to bust parts of this storm system making ice storms likely the hardest storms to predict. Nowcasting will play a big role along with every tenth of a degree for temperatures. Stay tuned for another short update tomorrow morning to see if it is a go for this forecast. Have a wonderful evening!!!
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