Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 9:21 PM GMT on January 07, 2009
Thoughts on January 9-10 storm...
Lack of confidence for forecast, therefore no discussion on storm. I believe that much of central Pennsylvania will be dry slotted and then as precipitation moves in, some of it will mix. Accumulations will be lucky to get to 4inches I think at this point. I am not one to give up on a storm, but I have had a bad feeling about this storm all week, just see my posts from a few days ago. I think these warnings may bust badly. I-80 corridor and northward is place to be as frontogensis places heavy snow band at that location. A sharp cutoff can be expected to the south. Then as precipitation moves in due north of low, mixing will take place. What we need to setup is a good initial band across central Pennsylvania as indicated by some earlier model runs on the 700mb RH moisture charts. Whether that will happen or not is a guestion. I have a feeling some areas in York and Lancaster will really get shafted. In any case I hope I am wrong, but this is how I see things this evening. And I would rather feel good to know that I am firm with my gut than stick with the NWS forecast of warning criteria snowfall just because they have a winter storm warning.
This is my current rain/snow line...
This is my experimental snow/mix/rain lines. These lines may adjust up to 25miles north or south, but they are my best estimation at this current time. This precipitation line is for the height of the storm, some initial snowfall to south of the lines is expected.
My rain/sleet line is... Deep Valley (Greene County) - Morgantown, WV - Frostburg, MD - Frederick, MD - Manchester, MD - Delta (York County) - Oxford (Chester County) - Wilmington, DE
My sleet/snow line is... Pittsburgh (Alleghany County) - Latrobe (Westmoreland County) - Johnstown (Cambria County) - Bedford (Bedford County) - Shippensburg (Cumberland County) - Middletown (Dauphin County) - Ephrata (Lancaster County) - Quakertown (Bucks County)
These are overall precipitation types. Precipitation types can wander several miles on either side of the lines.
1. Significant, widespread snowstorm.
2. Largest snowstorm for Pennsylvania for the winter season.
3. Mixing will cut down on accumulations for border counties.
4. Snow ratios near 13:1, 15:1.
5. Quick moving system.
*Note the southern part of the 5-9inch will more likely be 4-8inches.
Selected City Accumulations for the Northeast...
Hagerstown, MD- 1-3inches of light snow. Freezing rain up to .1inches.
Baltimore, MD- Light snow/sleet then rain. C-1inch of snow.
Washington, DC- Trace of light snow/sleet then rain.
Wilmington, DE- Light snow then rain. 1-3inches of snow.
Dover, DE- Trace of light snow then rain.
Cape May, NJ- Rain up to .5inches.
Trenton, NJ- 2-4inches of snow then sleet and rain.
New York City, NY- Moderate snow mixing with sleet and rain. 3-5inches of snow possible.
Poughkeepsie, NY- Heavy snow likely. 6-10inches of snow.
Binghamton, NY- Moderate to heavy snow likely. 5-10inches of snow.
Albany, NY- Moderate snow. Snow accumulations 4-8inches.
Hartford, CT- Heavy snow likely. 6-11inches of snow possible.
Concord, NH- 3-5inches of light snow.
Providence, RI- Heavy snow with some sleet. 5-9inches of snow.
Worcester, MA- Heavy snow likely with 6-10inches.
Boston, MA- Heavy snow. 6-10inches of snow likely.
Nantucket, MA- Moderate snow with some sleet. 3-5inches of snow.
Hyannis, MA- Moderate snow with 3-7inches.
Portland, ME- Light snow. 2-4inches.
Bangor, ME- Light snow. C-1inch of snow.
"Subject to Change"
After one of the most frusturating groups of model runs, we are now finally coming to a consensus. Model blend for my forecast consists of NAM/GFS/GGEM blend with EURO only for idea of mixing farther north. Models took a while to come on a solution as the EURO had a much more amplified runs and took the low well to the north. Meanwhile the GFS was the southern outlier along with the UKMET and showed the low crossing through central Virginia. As we got closer to the event, the NAM provided a middle ground solution and held ever side consistent with it generally trending only a bit to the south. The new EURO has now come around to a NAM track with similar temperature profiles. Track of 850 vortex low seems pretty consistent for all of the models tracking across central Pennsylvania between I-80 and the turnpike. This will cause mixes to occur generally to the south of the turnpike as a sliver of warm air sits at around 900-950mb. Timing is a major issue with the models as the NAM seems to be very slow with the system and even the latest 18z NAM does not show bulk of precipitation until the 24hour mark. Looking at the GGEM model it currently is the farther north, tracking the low across the Turnpike and bringing the H85 0C line as far north as just south of I-80. But during short term predictions I do not advise using the GGEM as the resolution is lower. The Canadian RGEM is a better high resolution model and takes the system very similar to the NAM with similar temperature profiles. The GFS finall came around to a slightly farther north solution taking the low just south of the Mason-Dixon line and that seems to be a good track. Personally I think the GFS has the best hold on this storm with temperature profiles, track, and QPF. Here is the simulated radar from the HIRES NMM for the height of the system...
As you can see it is pretty widespread with precipitation. Here are the final QPF totals for the GFS...
This a relatively sharp gradient, so that will need to be monitored in the form on Nowcasts.
After the storm...
Good Wednesday afternoon!!! This is the only section I will update for today, but there is a lot to talk about. So far I am very pleased with how my winter outlook is unfolding. Cold temperatures have dominated the winter so far along with snowfall +-1-2inches of normal, which is my call. It does appear we are entering what I believe to be the main theme of January. Who is ready to board the clipper express? Extreme cold air has been bottled up in Alaska for quite a while part in response to an unfavorable polar vortex over the region. A shift in this vortex will occur. This vortex is part reason why storm tracks have been through the Great Lakes and Ohio Valley. Lets first look at the teleconnections... The NAO is sharply negative currently with a negative PNA. The negative NAO is balancing out the unfavorable PNA resulting in near normal temperatures for the time period. Right now if we had less blocking and a positive NAO, I think we would be quite mild. The NAO is trending towards a positive state. Now in the past massive swings like this have been accompanied by major storms systems along the coast. In fact all major snowstorms on the east coast have showed a negative to positive trend in NAO. But for now models are speculative to anything of that occuring. 0z GGEM from Wednesday morning had a tightly wound cutoff low inland bombing out, but that scenario seems unlikely for next week. The AO index is positive currently and will be trending sharply negative during the time period of this arctic blast. The PNA lastly is going to be positive through this time period. The EPO and PNA being in favorable conditions along with the negative AO should balance out the effects of the positive NAO. Another major feature resulting in this highly cold period coming up is the dramatic shift of the MJO. Over much of December it was in phase 4 trending to phase 5, which favors more of a midwest and western US trough axis resulting in inland runners. Now finally we have moved into phase 6 and possibly into phase 7 which is ideal for an east coast trough axis. Something of concern is the La Nina that has developed quite impressively over the central Pacific with temperature anomalies near -1.1degree. Now there has been a few signs of warming waters very gradually surrounding the cold anomaly region. Also I have found from the past that La Ninas typically peak in early winter with a gradual decrease or otherwise known as warming of sea surface temperatures. All ENSO/SO climatic schemes are different and they cannot be put into judgement on further exact forecasts for future, but in this overall pattern the SO is the bust potential.
So now onto global models. They are in fair agreement for a severe arctic blast lasting from midweek next week through at least January 21, nearly a seven day period. H85s are near -20C with even a core of -30C across southern Canada. Surface temperatures likely resulting in negative numbers in some areas and single digits. While this seems extreme, it is all of the models showing this. EURO at times has been even more extreme showing polar vortex over the Great Lakes. This will result in likely a few lake effect snow outbreaks and many clippers. The latest 12z GFS from Wednesday afternoon makes this an evident idea with clippers moving in every few days bringing colder and colder air, snow ratios for some of these events may be near 30:1 across the north. The coldest temperatures look to be in the 10day mean with strong riding on east coast. Also another evident sign of cold air will be the positive anomalies across much of Alaska. Temperatures will be quite bitter for several days with gusty northwest winds under a times tight gradients. This will likely be the coldest period of the winter. Also I apologize for not issuing a January formal outlook, but it does seem like the month will be below normal for average snowfall for all across Pennsylvania. It has already started off very wintry and this is likely to continue. Stay warm all!
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- C-1.5inch of snow
Monthly Total- 2.00inches
Seasonal Total- 12.45inches
Winter Weather Advisories- 6
Winter Storm Warnings- 1
Ice Storm Warnings- 1
Blizzard Warnings- 0
Freezing Rain Advisories- 0
Winter Storm Watches- 3
Lowest High Temperature- 14degrees
Lowest Low Temperature- -3degrees
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
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.