Friday, October 04, 2013

Karen Still Churning Through Gulf

25-30 mph upper level winds are having their way with Tropical Storm Karen in the Gulf of Mexico, shearing off thunderstorms from near the center to a good distance east. You can see the swirl that depicts the actual center of Karen to the south of Louisiana, with thunderstorms firing and active to the storm's east. That wind shear will continue through today before slackening some tomorrow. Karen may have one more chance at strengthening before landfall but even with diminishing upper level winds the heat content in the northern Gulf is not incredibly great. Karen probably comes ashore as a tropical storm, perhaps on a strengthening trend.

Modeling has flip-flopped with regards to Karen's trek up the coast. The GFS, which had been consistently more progressive with Karen's track and push of moisture into our region has instead slowed its track after landfall down tremendously and spins the post-landfall zombie remnants of Karen across the Southeast and Carolinas for a few days. We get some rain with the front on Monday but due to the lack of phasing between the remnants of Karen and the front our rains aren't as significant as depicted on the Euro, which shows a full and total slug of rain working on through the Northeast as Karen gets pulled along.

The timing, as of now, looks like mainly Monday and Monday night with rains (and probably some thunder as well) as the front and whatever remnant moisture of Karen we get entangled along the front.

The GFS has historically shown a better track record the past several weeks with regards to weather locally and had shown the faster push that the Euro is now showing.  We'll keep an eye on the modeling flip-flops and see if this is merely an aberration or the start of a real shift in thinking with Karen post-landfall. The separate look that the GFS is suggesting in last night's run would produce slightly less rainfall locally (1/2-3/4" at the coast, up to a couple of inches inland) than the Euro (1" at the coast, up to 3" west of I-95). Rainfall likely isn't enough to cause significant problems given we're a bit dry of late but some of the usual suspect spots that flood easily could have some minor issues.