INCREASING THREAT FOR MAJOR WINTER STORM FOR TENN VALLEY AND MID ATLANTIC FEB 4–5 .. WOOF?
One of the rules I try to convey to people who have some interest in weather and understanding how weather forecasting process works is that while it is true that the regular deterministic or operational weather models (GFS EURO CANADIAN etc) beyond 4 days become increasingly unreliable when it comes to figuring out large-scale weather patterns and changes…. using the Ensemble and the ensemble mean of a weather model from 72 hours out to 15 days is actually quite useful and reliable especially if you know what you are doing.
Let’s assume for a second the day 7 operational or regular Canadian model is showing a snowstorm for Chicago and you being a winter weather lover and a snow nut near Chicago…. you are very concerned and potentially quite happy. What you want to do is compare the regular or operational Canadian to the Canadian ensemble to see if they match AND to see if the solution makes sense from a weather point of view.
CLEAR?
In the previous edition of THE NEXT 3 WEEKS Newsletter on January 22nd and in the video January 23rd I talked about how the warm pattern was going to end MUCH sooner than expected AND lead a sudden dramatic reversal to a much colder and stormier pattern for February.
And over on the Twitter page wxrisksnowstorm and on the wxrisk THREADS pages I posted this on January 25
…MAJOR CHANGES AT 500mb ACROSS NORTH AMERICA WILL END MILD PATTERN MUCH SOONER THAN INITIALLY THOUGHT…..
I talked about a process known as UNDERCUTTING caused by the development of the “Pamela Anderson” 500mb pattern.
That is to say the development of a MASSIVE Trough along the West Coast of CALIF and a series of large UPPER LOWS dropping down from eastern Canada into the Mid-Atlantic then out into the Western Atlantic Ocean during the next several days. This would cause the RIDGE over the Plains to expand extremely rapidly and get pushed northward into south-central Canada where it would become a monster BLOCKING pattern.
The result is the development of new cold Arctic HIGH pressure system driving cold air back into the eastern CONUS….. all the while the never ending Pacific jet stream will continue to blast energy into CALF and the SW states across the lower Plains and into the Gulf Coast setting the stage for potential significant Mid-Atlantic winter storm February 4- 5.
The 0z Saturday op-European model showed exactly that as it brings a historic record shattering snowstorm to much of Virginia (24 -28inches at Richmond ) and major snowfalls to DEL MD WV and western NC.
Moreover, the position of the monster BLOCK in south central Canada AND the large UPPER LOW off the coast of Maine would ensure that any LOW pressure area that developed in the northern Gulf Coast areas along the frontal boundary can only track in the East or ENE direction. This would imply a very sharp north were cut off to the snow boundary — -so for example in this possible outcome that might not be any significant snow north of the PA Turnpike
IMAGE 1 and IMAGE 2 shows exactly how the situation COULD develop according to the 0Z op ECMWF valid FEB 3–4–5.
That being said, it is quite possible this solution may not be correct at all. Loook… there is NO doubt that the El Nino driven southern jet stream energy IS going to undercut the huge block that forms in south central Canada.
The combination of this massive split flow jet stream pattern with the huge BLOCK in south central Canada and the incredible southern Stream Energy moving into the lower Plains and the Gulf Coast — — offers a extremely high probability KU major or historic winter storm, with HIGH RSI /NESIS values for somebody in the eastern US sometime around February 4 or 5.
(if you are weather nut/ hobbyist/ weenie etc and you dont know what RSI or NESIS is when it comes to east coast winter storms… then shame on you! )
THE KEY==== what happens in the northern Jet stream in the first few days of FEB .
The 0z Saturday operational European has been dropping these powerful pieces of energy or short waves in the northern jet stream from western Quebec Canada into the Great Lakes then through the Mid-Atlantic that then swing up into SE Canada.
IF… that is correct and there is a large closed UPPER LOW south of Nova Scotia on February 2–3–4 …IF…. then the significant LOW pressure area that develops in the Gulf Coast will have very little north latitude movement. the system will essentially be Force attracting a ENE direction.
At this point I am sure you are saying …”hey DT get a grip you sick twisted weather freak!! This is 8 days out.”… Perfectly understandable
Soooooooo lets look at the 0z Saturday European ensemble (called the EPS). It clearly shows massive upper LOW in the TENN Valley on FEB 5. On top of that the BLOCK in south central Canada is very strong- of exceptional intensity at around 400dm above normal centered in south central Canada.
Experienced synoptic meteorologists KNOW that this 500mb pattern means that there is a large Arctic HIGH moving into the Great Lakes and driving the cold air southward while the huge and Powerful 500mb LOW in the Deep South / TENN Valley is generating a significant surface LOW .
So even if you don’t accept the 0z Saturday op-European model solution… the Ensemble is screaming snowstorm for the Mid-Atlantic and potentially the Tennessee Valley FEB 5.
***** 12z EURO
The 12z Saturday op-Euro has come in and it has a totally different solution with regard to February 5. It does NOT show a historic record shattering snowstorm for the southern half of the Mid-Atlantic region and the Tennessee Valley on February 5.
However the 12z European Ensemble on Saturday afternoon looks exactly like the 0a Saturday European sample. BOTH of these 500mb maps are screaming snowstorm for the Tennessee Valley in the Mid-Atlantic region for February 5.
When we compare the 12z EPS to the 0z run of the European Ensemble we see the same sort of thing. The Saturday 12z EPS still has a MAJOR LOW the TN Valley with arctic HIGH pressure coming down from the Block in south central Canada. In other words, the Saturday 12z EPS is IDENTICAL to the 0z Saturday EPS run for FEB 5 and is very strong signal for a major Middle Atlantic snowstorm for February 5.
