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June 2012

Debby Weakens but Still Soaking Florida – Atlantic to Turn Quiet after She is Gone

   Posted by Levi at 2:05pm on June 25, 2012

Debby continues to meander slowly in the NE Gulf of Mexico this morning, and is currently drifting ENE. Convection has waned throughout the core, a function both of the continued wind shear that was talked about yesterday and cold upwelling of the ocean due to Debby’s stalling for so long in the same area. She has weakened since yesterday and now has only 50mph winds, though rains on the eastern side continue to affect Florida, where flooding has been a problem. Florida will continue to receive more rain until Debby’s center crosses the peninsula, which is where Debby is now headed.

The track forecast for Debby within the last 36 hours has gone from every model except for the GFS and the NHC track itself taking the storm into Texas, to a swing eastward over Florida, and yesterday afternoon I was forced to change my track as well. Although this was likely the most difficult track forecast we will have to make this entire year, and the possibility for a Florida landfall was always on the table, it was still a bust, and something to learn from. I show in the video the most logical reason for why the forecast failed, that being the pattern amplification over North America that was not conducive for a ridge orientation that could block Debby underneath. Overall Debby’s forecast was a mixed bag, as we have been talking about her development for a full 2 weeks with the potential for an Allison-type rain event for the gulf coast, and this along with the intensity forecast verified, but the track did not come through.

Debby will be taking her sweet time in crossing the Florida peninsula, and once on the other side the state will likely dry out, but Debby may still move very slowly and hang near the Gulf Stream for a while, possibly restrengthening. The latest Euro bombs her to a major hurricane over the Gulf Stream, but the pattern with the trough over the east coast would prevent a 2nd landfall, and will likely steer her northeastward out to sea eventually.

After Debby, the Atlantic will turn quiet again as the MJO starts to leave the basin. The upward motion provided by the MJO is rather necessary before August to get any significant development, and until the MJO comes back around to the Atlantic, much of July may be uneventful. In general, as we get closer to the peak part of the season, activity relative to normal should decrease, typical of El Nino seasons, which favor development early and then tone it down during the peak of the season.

Although this was the fastest start to the hurricane in the record books in terms of storm count, Debby was the first truly tropical development of the year, and this is nothing like the 2005 season. This season should still end up near or slightly below normal in terms of overall activity, with the potential for slightly inflated number totals due to all of the subtropical-based developments that we had in May and June. Indeed, the last time a season started this fast before July was 1968, when 3 storms formed before July, but in the end the season total was only 8 storms. Unsurprisingly, this was also an El Nino year, and this season should follow the same general path, though I expect storm totals will be 10-12 by the end.

We shall see what happens!