A developing tropical cyclone off the coast of Florida and The Bahamas will likely have some impact on our weather later this week. While a direct hit seems highly unlikely, some of the moisture associated with “Arthur” will likely stream up the coast and may produce a band of heavy rain somewhere in southern New England either Thursday or Friday.
Our computer models are beginning to indicate a possible “Predecessor Rain Event” or PRE well north of Arthur later Thursday. There has been plenty of research on PREs – Bosart and Carr (1978), Cote et. al (2008), Galarneau etl al (2010) to name a few – and Arthur may produce a PRE over Connecticut later this week. Here is a conceptual model of a PRE from Cote et. al which is a nice illustration of the synoptic and mesoscale features that coexist for a PRE.
In this case, Arthur will be approaching the Outer Banks of North Carolina with the northeastern U.S. in the right entrance region of a strengthening jet streak.
While the mesoscale details will need to be ironed out as we get closer to the event we’ll have to watch for a period of excessive rainfall later this week. It’s possible that some areas will see flash flooding though it’s too soon to say exactly when and where.
Additionally, we’ll have to watch for severe thunderstorms on Wednesday afternoon and Thursday afternoon. A remnant plume of elevated mixed layer air will be moving across New England with gradually increasing deep layer wind shear. It is possible we remain capped on Wednesday (700mb temperatures near or just over +10C at least initially – late show??) but by Thursday any capping will be eliminated and convection will be widespread.