Potential Major Storm for Eastern US for January 26-27...
Current wavelengths are supporting a large synoptic storm east of the Mississippi River Valley during the January 26th to the 27th with widespread moisture from the Southeaast to New England. This setup is corresponded with highly favorable teleconnections. The NAO (North Atlantic Oscillation) remains negative but has shifted the higher heights more east-based. This causes less blocking upstream. Blocking is typically associated with suppression and tracks of coastal lows well over 100mi off the coast. Also blocking allows for a slower movement of low pressures ushering in cold air to the right of the low in the large cold sector of the storm. When the blocking is allowed to relaxed or becomes displaced as in this instance, it allows cyclogenesis to often occur a bit farther to the west offering warmer air with a southeasterly flow off the Atlantic. This upcoming coastal threat will favor the later with dampened upstream blocking. Also the MJO (Madden-Jullian Oscillation) is entering phases 7-8. The MJO is a measure of the positioning of the monsoonal rains across the Indian Oceans. Since all global weather patterns are interconnected, differing wavelengths of pressure in the Indian Ocean will in time affect areas downstream in the jet stream across North America. Here is the current composite 500mb mean charts for an MJO phase 7 during January from a meteorological study by Allan Huffman...
Link
As noted above, increasing ridging across the western United States with a deep trough over the east coast often occurs. This corresponds to the current teleconnective pattern over North America with a positive PNA (Pacific/North American Pattern) which favors high pressure over the western United States coupled with upper level ridging.
The teleconnections are certainly signaling the classic jet stream setup for eastern cyclonegesis. But several 'issues' will likely prevent a major east coast snowstorm for areas in the major metropolitan region of the United States. Paul Kocin and Louis Uccellini's monograph of Northeast snowstorms signals the classic setup for widespread historical snowfalls to be accompanied by an arctic high pressure to the north of the storm. Typically we would root for a large anticyclone to the north or north-northeast of New England across southern Canada. This helps usher in cold air funneling in the western periphery of the low pressure. Also this helps prevent the low pressure from running too far inland.
The current synoptic setup shows the high pressure to the north of the low quickly scooting to the northeast and eventually too far east to save many from the expected rainfall. The 1/21/11 12utc ECMWF shows the banana high displaced to the east in an unfavorable location.
Kocin/Uccellini's near miss historic east coast snowstorm often featured a high pressure in a similar displaced location. Typically this would then favor inland snows with a mix or rain across eastern areas. While a severe arctic air mass will be in place along with a fresh snow pack over the Northeast, oftern these air masses can disperse quicker than one would assume. Current GGEM/UKMET/ECMWF guidance supports the upper level trough becoming negatively tilted towards the easteern Mississippi Valley. With these higher amplitude trough, the banana high is quick to depart and allows the cyclogenesis to occur farther along the coast. The 1/21/11 12utc GFS shows this evolution a tad differently, but does appear to be an eastern outlier. The 12utc GEFS mean shows a farther west solution, which often argues that the operational model is too far east. Most of my analogs support the heaviest snows well northwest of I-95 as warmer invades from the east. Despite several global models showing the low becoming vertically stacked allowing H85s to crash, there will likely be a southeast maritime flow across eastern areas.
The track of the H5 low tracks across Virginia, which is a bit too far north for a favorable snowstorm for most areas south of Washington DC for certain. Given the departing arctic air mass I would expect areas that receive mainly rainfall still to receive snow accumulations on the front end of the storm. The ECMWF mentioned earlier supports a quick 4-8in along most of I-95 before rainfall.
At this point, those farther east will be hoping to look for the 500mb low to track farther south, the banana high to become more situated north and not northeast, and the exact placement of the negatively titled trough.
While the threat is several days away, current climatology and guidance supports a very high threat of a large storm system over the eastern United States in this time frame. Whether it is rain or snow, there appears to be a large amount of moisture involved with ECMWF QPF up to 4in in northern Delaware and southeastern Pennsylvania. I know many are critical of predictions of storms well in advance, but meteorology is about understanding the synoptic setup that leads to the development of these storms. Watching the evolution of this situation will be very interesting and I am becoming increasingly enthused for those well inland. Even along the coast heavy rain and high winds are possible with a western storm track so threats will be high with any storm scenario. Stay tuned for updates throughout the weekend. For now if I had to make a forecast, this would be the precipitation scenario map.
The exact placements of the trough/shortwaves/high pressures will change, but I have not seen such consistency in the computer models for a large event in a very long time. This is also backed up by a favorable wavelength pattern as mentioned earlier in the blog. I think there is a higher possibility of this tracking farther west and inland than it tracking east. The odds of all snow along I-95 to the coast remain low given the departing high pressure. Another concern is the poor modeling this winter and the trend for storms to phase later than expected. Something to keep reminded of... Stay tuned!
Short Computer Model Introduction
This is a pretty decent quick intro on computer model forecasts along with beneficial links. Computer models use the complex calculus algorithms to print out the forecasts. Despite our complaning with the models, without them much of us would be lost except in the short time. Some of the earlier computer models consisted of the ETA, NGM, and AVN, which forecasted generally less than 84hrs. They were highly inaccurate, but provided a basis. The ETA was actually the computer model that helped meteorologists predicted the "storm of the century" in March of 1993 so well in advance. But now more than ever we have a myriad of computer models available to the general public with many mesoscale models only available to NOAA. Lets start with the general. All current computer models are based off on the Zulu time. Zulu time is also known as UTC or Greenwich time . Generally to forecast timing of storms my special BUFKIT data transitions UTC time to EST time, which is helpful. But BUFKIT is a special download, which I won't get into, but the transition is helpful as for some reason I never am able to understand time zones too well, hahaha. Anyways let me start with each computer model...
-GFS (Mentioned most of all as it is a global model (Global Forecasting System))
~Available in 0z (initiates at 10:30pm), 6z (initiates at 4:30am), 12z (10:30am), 18z (4:30pm)
~Forecasts out to 384hrs
~Typical biases
Cold bias on long range on 18z run
6z and 18z slightly unreliable
Northwest trend on lows within 84hrs of event
-ECMWF (This is another global model run by an international organization (European Centre for Medium-Range Weather Forecasts))
~Available in 0z (initiates at 1:30am), 12z (initiates at 1:30pm)
~Forecasts out to 240hrs
~Typical biases
Overphases lows in 168hr range
Holds too much energy in southwest
Known as extremely accurate within 140hrs
-NAM (Mesoscale short range model)
~Available in 0z (Initiates at 9:30pm), 6z (Initiates at 3:30am), 12z (initiates at 9:30am), 18z (Initiates at 3:30pm)
~Forecasts out to 84hrs
~Typical biases
Highly inaccurate towards the 84hrs
Handles coastal storms very well and southwest overrunning events
Tendency for way too much QPF
Those three above are the most common models for a beginner in computer models, but there are many more. All of the global models consistent of ensemble models also, such as the GFS has a myriad of ensemble (small models) that create a mean solution known as GEFS. They typically are too cold and southeast with low pressures, but some reason the NWS seems to enjoy using them. There are also more global models than the GFS and ECMWF... The UKMET is run by an internation organization and forecasts out to 144hrs. This model typically comes out an hr before the ECMWF and usually is pretty similar to the ECMWF. The ECMWF may also be known as the EURO by the way. There is also a Canadian model known as the GGEM/CMC, which again contains ensemble models. All of the internation models only run 0z and 12z runs. This is probably for the best as all models only receive new upper air data in 0z and 12z runs, so this is why the American model runs of the 6z and 18z are usually worthless. There is also a high resolution Canadian model known as the RGEM, which is very similar to the American NAM. High resolution (mesoscale models) are important as they usually are able to pick up on fine details such as frontogenesis, advection, adebiatic cooling, convection, etc. Some of this high resolution models include the WRF, HIRES NMM, RUC, ARW. They all are usually very accurate, but the WRF and HIRES NMM usually have wet bias.
As mentioned above there are ensemble models which come up with a mean solution instead of using one computer model's algorithms like the global models use. These ensemble mean solution are known as the MREF and SREF with MREF being in the medium range and SREF in the short range. SREF is usually pretty accurate and forecasts within 87hrs of an event. There are also other computer models used for hurricane forecasting, but I will not get into them. For instance one is the GFDL, which you may have heard of. I find I use mainly the GFS, NAM, and WRF/NMM in the summer, but use all of the models in the winter.
A few models to avoid...
JMA
KMA
CAMPASS
DGEX
Here is a list of links for explanations on how to interperate the models...
-PennState E Wall, which runs all of the models
http://www.meteo.psu.edu/~gadomski/ewall.html
-PennState E Wall tutorial on computer models (Check it out)
http://www.personal.psu.edu/adb241/eWallTutorial/ Main.htm
-Severe Weather parameters used on models, explanation
http://www.crh.noaa.gov/sgf/n=severe_weather_chec klist_paper
-Forecasting winter weather
http://www.crh.noaa.gov/lmk/soo/docu/precip_type. php
-NCEP; used to find American Computer models
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/
-Severe Weather Models
http://www.wxcaster.com//conus_0012_us_models.htm
-Winter Weather Models
http://www.wxcaster.com/conus_snowfall.htm
-Model Soundings
http://wxweb.meteostar.com/sample/sample.shtml?te xt=KMDT#
The last link is listed above as model soundings which takes all of the data to print out all sorts of information including precipitation type along with dynamics such as Omega. This is very complex and takes some time getting used to. Also you may see this data instead of in charts, it is sometimes used in SKEWT T charts.
I hope all of this information helped out... Keep in mind precipitation amounts is QPF, with 500mb aloft being the jet stream, 700mb aloft measuring relative humidity, 850mb aloft measuring 5,000ft aloft temperatures, 925-1000mb measuring surface temperatures. Generally I would look at the GFS and NAM first to get a hang of it along with reading the tutorial links. Use the 850mb and 2m charts for the GFS especially as they are pretty self explanatory and color coded. You will find some maps for international models are confusing and black and white.
"Here northeast of Harrisburg 2010-2011 winter statistics"
(Snow Stats)
Current Snow Cover- 1-4in
Monthly Total (November)- Trace
Monthly Total (December)- 0.6in
Monthly Total (January)- 11.65in
Seasonal Total- 12.25in
Winter Weather Advisories- 5
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 1
(Temperature Stats)
Lowest High Temperature- 23.7F
Lowest Low Temperature- -1.7F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First accumulating snow - December 10 - 0.50in
Clipper light snow - January 7-8 - 2.25in then another 1in
Double Barrel Low - January 11 - 4.5in of snow
Coastal Low - January 17-17 - 1.8in of snow/sleet
Arctic Front - January 20-21 - 2.1in of snow
Lower Susquehanna Valley Doppler...
(Courtesy of WGAL)
This is the most difficult forecast I have ever had to make for the region. The gradient is going to be very sharp across the north and will make for a very high bust potential. This map is a bit bullish for northern areas. We shall see. Enjoy!
"Here northeast of Harrisburg 2010-2011 winter statistics"
(Snow Stats)
Current Snow Cover- 4-8in
Monthly Total (November)- Trace
Monthly Total (December)- 0.6in
Monthly Total (January)- 18.15in
Seasonal Total- 18.75in
Winter Weather Advisories- 6
Winter Storm Warnings- 1
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 1
(Temperature Stats)
Lowest High Temperature- 23.7F
Lowest Low Temperature- -1.7F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First accumulating snow - December 10 - 0.50in of snow
Clipper light snow - January 7-8 - 2.25in then another 1in of snow
Double Barrel Low - January 11 - 4.5in of snow
Coastal Low - January 17-17 - 1.8in of snow/sleet
Arctic Front - January 20-21 - 2.1in of snow
Upper level/coastal low - January 26 - 5.75in of snow
Reader Comments
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I think Blizz's plan is a new blog soon on verification of the last storm, and then a blog on Monday on the next.
It looks to me like our area of Maryland could get a snow to freezing rain to rain storm, with GFS taking the main low north and west of us. HPC has a low in Kentucky. I'm a little worried about temps, with the prospect of cold air damming and ice in our area. We have a lot of snowpack to help keep surface temps down, and the models are saying that the arctic airmass pushing this next storm will be quite cold as it spreads over north of us. Look at the -30c line on GFS -- all the way down into PA. Granted that's a week away, so the model may be off base. But still, with this much cold air around, if some of that cold air is in place ahead of the storm anything could happen...
Duane Thomas ,a running back for the Cowboys back in the 70's,was asked,"How does it feel to play in the Ultimate Game?"..He replied;"If it's the Ultimate Game how come they play it every year?"
Blizz the Wizz must be workin' in his lab..let's see what he cooks up for us this time.
P451 we need your help, turn on your ground zero machine again , will ya ?
Thanks bwi. I will wait for a blog update.
That's a great quote! I'm just not a football fan.
It's always "just a snowstorm", there's always going to be another ULTIMATE STORM if we wait long enough:)
1)Will the data from the previous storm immediately be used in future modeling?
2) What caused that storm to explode like it did? Was it simply a timing issue missed by the models?
Nvrmnd. I looked at radar for first time in an hour and it's doing its usual thing. Clippers suck for us near the coast.
You obviously don't have Pepco!
I like that model! Time for northern New England to get a decent snowfall for a change. Lots of 3-4" over the past few weeks but a 2 footer is what we want now.
Well that would certainly put Philly at 4th or 3rd for snow this year, truly wild. This season's already only a few inches away from overtaking 2002-2003. Hopefully it won't try to challenge 2009-2010.
it was the only way to get back into this blog. i wonder if anyone else knows how to get back in?
Keep the link in your favorites or go to Blizz's new blog and enter 180 in over the 181 in the address bar.
http://www.wunderground.com/blog/Blizzard92/comment.html?entrynum=180#yourcomment
His new blog is 181. Also you need to ignore crowe1 to see the whole blog as there is an entry that is causing errors.
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