1815 EDT 28 OCTOBER
1700 EDT OCT 22
While we have had a few significant eastern U.S. Low pressure areas… so far in this cool season so far we have not yet seen a MAJOR East coast or eastern US Low. The data is increasingly showing that that is likely to change as we approach the end of the month with the potential for significant East Coast Low pressure area on October 28-29. Depending on the track and how the system develops the potential exists for significant early season snowfall over the mountains of eastern TN e KY of good portion WVA … southeast OH ..far western MD… western and central NY state … western and central PA far western MD. There could also be some snowfall occurring in the Pocono Mts of northeast PA … as well as the Catskills in eastern NY and the berkshires in western Mass.
Even though I shouldn’t have to say it …. let me be clear… This event… even in the cold est and worst case scenario… is NOT a threat for any sort of snowfall over any portion of the I – 95 big cities from RIC to BOS. There may be some other folks were talking about that– but you won’t hear it from me.
We will start out by look of the 0Z Saturday 10/22 run of morning European model. As you can see the model has a pretty strong low pressure area centered for close to Baltimore Washington, DC on the western side of the Chesapeake Bay.
The three images of the 0z euro show regional impact of the major coastal Low late Friday night in deciding morning over the Middle Atlantic states and over New England.
I have highlighted or drew in the rain snow line which you can see is mostly over the mountains of WVA western MD and PA.
In these next images you can see how the European models developing this major East Coast low. Essentially there are 2 pieces of energy — called short waves in the wx Biz that cause this coastal Low to develop. Th 1st one is over NM ( the southern short wave) and the northern s/w over the Upper Plains / MN. What is important to notice here is that the tilt or alignment of the 2 pieces of energy or short waves is SW to NE . This sort of angle or tilt is referred to as a “positive tilt”. Over the next two days the 0z European model at day 5 and day 6 slowly swing these two short waves around so that by the time they reach the Mississippi river / Delta the southern energy is now NEUTRALLY tilted… that is running S to N. The Northern energy is dropping into the southern Energy which is a process referred to as PHASING in the weather business. Whenever you have the two jet streams of phasing like this and the merging of two piece of energy it is always a sign that a major Low is going to form .
The 0z 10/22 British Model– the UKMET — strongly supports the European scenario. It shows the same sort of phasing or merging of the two pieces of energy over the Southern Mississippi River at Day 6.
Not surprisingly,… the 0z and 12z GFS model runs have a totally different solution with regard to the development of this potential system for OCT 28-29. Both model runs of the GFS show this MAJOR Low but the model develops the system much faster because it handles the upper atmosphere synoptic pattern Much differently. And because the Low forms much faster … the track is waaaaaay inland.
This image from the 0z 10/22 GFS shows the Jet stream (500 MB) valid for 8pm on 10/28.
The 0Z GFS model has a closed off DEEP Low over the Deep South that has developed a NEGATIVE TILT… this is where the tilt or alignment of the Upper Low is running NW to SE. The 12z 10/22 run of GFS continues to do this. This sort of RAPID phasing between the Jet stream is known ” bias” of the GFS Model.
These images — from the 12z GFS run –show how fast the model is swinging around the southern s/w froma POSITIVE to NEUTRAL to NEGATIVE tilt. A Classic case of the GFS Model over phasing .
On the other hand the 12z saturday EURO model has come out and seems to have backed off the BIG east coast Low idea.
These two images show the JET stream (500mb) maps and the surface maps at day 5 and Day 6. We can clearly see the southern energy over NM and the northern energy over the Upper Plains at DAY 5…… but at Day 6 the model seems to have totally lost southern energy!
Remember it is the PHASING of the two pieces of energy that causes the Big East coast Low. If the southern energy is gone there is NO phase and NO big storm.
Indeed that is EXACTLY what the 12z European Model at day 6 shows ..an ordianry Low over the northeast US.
I am not altering my forecast at all . I think the 12z GFS and 12z EURO Models are both wrong .