POTENTIALLY some good news for East coast Winter weather Lovers 2019-20
One of the important things that are overlooked in making the final winter forecast is the development of coastal LOW-pressure areas during the months of October and November which impact the East Coast. These might be inland coastal Low or actual true nor'easter but the point is to see how much activity there is in the southern jet stream. The idea is to get some decent activity in the southern jet stream which holds into the winter season. Remember that it is the southern jet stream that provides the moisture and the polar or northern jet stream which provides the cold air. So if you don't have an active southern jet stream... that chances of seeing the big East coast snowstorms become much reduced regardless of how much air there might or might not be. Of course the same is true the other way - you can have the most active southern jet stream the world but if you don't have the cold air then you have pattern / winter that will feature a bunch of cold rain.
As some may know there are generally two types of winter storms for the East Coast (actually there are 3) . There is a type of LOW pressure area that tracks through the Midwest that redevelops from Ohio Valley that "jumps" reforms off the Middle Atlantic coast. This kind of winter storm is referred to in the weather business as a (MILLER B) system. Generally MILLER B type -LOW redevelopment of the Mid Atlantic benefits mostly New England and not Middle Atlantic & Tennessee Valley areas.
However the classic big winter storm which comes roaring of the Gulf of Mexico and brings up heavy precipitation into the cold air over the Middle Atlantic and New England regions is refferred to in the weather biz as a MILLER A. These MILLER A-classic coastal LOW Noreaster usually have a lot more precip and it impacts reach deeper inland & covers more of the East Coast than a MILLER B.
so... an active southern jet means that a winter season is more likely to see MILLER A LOW pressure systems coming out of the Gulf of Mexico and impacting large portions of the East Coast. (this is of course assuming that recent trend of active the southern jet continues into the heart of the Winter.
The problem with this Autumn so far is that the first half of October was part of the hot and dry pattern from August and September and as a result there has not a lot of coastal activity. There was a weak coastal LOW on October 12 that became tropical storm Melissa in the Northwest Atlantic Ocean. This was followed by the more serious coastal LOWS on October 16 -17 which was followed by another system on October 20 21. Since then there have been a number of strong cold fronts which it move through the eastern third of the country that has provided significant rain but in terms of any more coastal LOW pressure areas there have been none since OCT 21.
However, that appears to be changing.
The various weather models continue to show a very strong and active southern jet stream with a major piece of energy moving over the Southeastern states this upcoming weekend November 15 -16. At the same time the models show a very strong and large Canadian HIGH pressure system over the Great Lakes and New England. If this was an arctic HIGH pressure system or one that was later into the heart of the winter ... then this November 15 16 coastal LOW pressure area could set up a significant snowstorm for much of North Carolina Virginia and perhaps Maryland and Delaware. But again the air mass associated with this large semi cold HIGH on November 16 over New England does not have enough cold air with it to keep the warm air from the gulf stream from coming northward with the LOW pressure system. As a result most of the precipitation of falls is rain.
There is some uncertainty as to how much rain is going to come northward but certainly North Carolina South Carolina Georgia will have a major rain event on November 16 -- that might start on the 15th- and some other rain will get into the southeastern third of Virginia on the 16th as well. As you can see both the GFS and the European models have this is a very slow moving system that only slowly drifts off the Carolina Coast on the 17th. Again if this was the heart of the winter this could be a major snowstorm for the lower Middle Atlantic region.
Then after that system moves away the weather models show the northern jet southern jet streams phasing or merging over the Mississippi River valley and the Delta on November 18. This results in producing another coastal LOW starting in the northeast Gulf of Mexico that moves up the Southeast coast and provides rain for much of the East Coast from Georgia into Pennsylvania and possibly New York on November 19 - 20. This second system shows up as a SIGNIFICANT coastal LOW that tracks close to the coast and is fairly strong on early WED morning European and GFS models.
Assuming that the weather models are correct with these two systems over the next seven days this would give us a fairly adequate number of southern coastal Low pressure areas developing in or next to the southern jet tream as we go into the heart of the winter. This can only be viewed as an encouraging sign for people who like East Coast snow storms.