Special Edition Of WEATHERAmerica Newsletter, Monday, September 22, 2008

Upcoming Event For The Eastern Seaboard: Disturbed Frontal Structure And Possible Landfall Of Tropical Cyclone (Kyle)

The potential exists for a complex heavy rainfall and strong wind event along the Eastern Seaboard between Wednesday and Sunday. I say "complex', since the unfolding scenario includes a packed pressure and thermal gradient, a subtropical disturbance, strong IcP anticyclone and perhaps even a hurricane!

With moderately strong high pressure building across New England into Nova Scotia, a subtropical disturbance now taking shape over the western Gulf of Mexico will create an impressive gradient between SC and S NY at midweek. Overrunning and orographic processes generated by the tightening distance between the low and high will complement the gusty surface winds, with 3 to 5 inches of rain possible during the first part of the sequence in N SC.....NC....S VA....E TN.

There is a fairly wide variety of forecasts for the track of the tropical cyclone, which should start to influence sensible weather around Thursday night. If it is correct to assume that the disturbance now straddling Puerto Rico becomes a depression and then a named storm (Kyle), the direct flow of tropical moisture into the frontal structure off of the East Coast will begin to enhance rainfall rates from VA into the Delaware and Susquehanna Valleys. The GFS version and the statistical tropical schemes see only minimal rain and wind from the Kyle circulation reaching the Interstate 95 corridor. However, the ECMWF, GGEM, and many of the dynamical equations show a fairly strong impact in NJ, S NY, CT, RI and MA, with the Canadian, GFDL and HWRF showing a worst-case situation involving more than 5 inches of rain, storm force winds, and a noteworthy coastal surge/flood this weekend.

Something to keep in mind before accepting the "out to sea" path: all of the numerical models feature a fairly vast 500MB weakness covering the eastern third of the U.S. while also illustrating a very gradual exit of the anticyclone through Maine and Nova Scotia. With a solid majority of these predictions favoring a Category 2 peak strength, it is not inconceivable that the system possibly known as Kyle will follow a north-northwest path into the New York NY metro area, followed by a slow rightward turn with rain and wind concerns for New England.