Sunday, October 21, 2012

For Now, Don't Believe The Model Hype

Funny how some tropical moisture and thunderstorms that have not organized into a tropical entity yet can create model havoc over a week from now on at least one computer model.

This tropical entity, which should develop into something during the coming week, will track through Hispaniola and Cuba and into the Atlantic. From there, there's a lot of uncertainty on its final path. Adding to that uncertainty is the interaction between the tropical entity, whatever strength it may ultimately obtain, and the eventual cool down that works into the Mid Atlantic for next Sunday-Monday.  Our Indian Summer will halt and reality checks back into the our world with temperatures that will be much more typical, if not cooler, than average to close out the month.

This trough-storm interaction is still a week plus from playing out but the models are having fun trying to spit up fascinating scenarios that are a bit out of reality.

If you want to believe what the Canadian/Global computer model spit out last night, the hype machine would be in full gear as the Canadian combines the tropical system with incoming cold trough, creating a storm system that gets captured and stalls out near Washington, DC...moving very slowly for a two to three day window as the low gets cut off from the main jet stream.  This scenario, which is the most extreme of the modeling right now, suggests mountain snow, lots of rain for us, and also a good deal of wind.

The good news, unless you like model extremes, is that no other model shows anything similar.  The GFS shows the approaching cold trough in the Midwest but that trough does not capture the tropical system and phase it into a major storm in last night's run. It's a bit more "realistic" in component except for the feedback with the secondary low in between the low above the Great Lakes and the tropical system near Bermuda.

The Euro is the slowest with the development of this event but does show the potential for a coastal low developing from energy with the tropical entity early next week, a bit later than the other modeling.

Anytime you get a trough diving down from Canada in late October and early November and a tropical system in the Caribbean, there is potential for some crazier weather.  Lili in 1996 enhanced a cold frontal passage in New England and gave them an excessive rainfall event.  Noel in 2007 brought rain and snow across Eastern New England as its nontropical remnants paralleled the East Coast.  Of course, we all know about Hazel in 1954 and its impacts to the Carolinas, the Mid Atlantic, and Toronto.  Hazel is an extreme analog, as extreme as what the Canadian computer model suggests.   Don't believe the model hype in this case, at least at this point.