Clark
(Meteorologist)
Tue Sep 02 2008 08:48 PM
Hanna, Ike, Josephine - oh my

Hanna's quite the interesting storm -- atypical development, ingestion of an upper low, acquiring subtropical elements, prolonged intense convective burst in the face of Gustav-enhanced shear, and today weakening in the face of that shear. What changed today versus yesterday? Most likely the orientation of the shear and the location of a deformation axis, or area where winds come to an axis and "deform" in all directions on either side of it. Yesterday, it was in a highly diffluent area along the deformation axis, but today the upper trough along the east coast has dug a bit further south and pushed that axis away. Hanna is left in an area of weakened steering currents, waiting for the pattern to change slightly, only moving as the center continues to try to redevelop underneath the convection. Since the convection redevelops downshear, the center moves (or reforms) south. Eventually this will end and Hanna should move to the NW, paralleling or running along the FL east coast before landfall in the southeast US, but it's not going to end today.

Ike behind it is chugging along westward underneath a ridge that keeps progressing westward with it. As Ike nears Hanna, the pattern should begin to change and keep the two far enough apart from any significant interaction, but given the large size of Hanna's circulation it's not out of the realm of possibility that northerly shear from Hanna ends up impacting Ike, especially if Hanna moves slower than forecast. Otherwise, conditions appear fairly ripe for Ike with the NHC 11a discussion doing a great job of some of the factors at play. There is a bit of uncertainty in the long-range steering patterns, an uncertainty that only increases if Hanna doesn't start moving as it is possible that the storm could help lift Ike further northward. That's being discounted right now given the lack of evidence in the model forecasts, but it's not impossible.

Josephine's likely a fish. NHC package looks good there, with intensity leveling off in a couple of days as it nears cooler waters. Near-Africa waters in the Atlantic are running above normal for the first time in a few seasons, helping to fuel these storms so far east.

The next wave over Africa is very well organized already and stands a chance at developing in 2-3 days after moving over the open Atlantic. Several models suggest this to occur, developing a fairly intense storm for such easterly latitudes. While that is probably a bit over done, it's quite likely that we've got another storm to deal with before the end of the week. 'Tis the season for such activity -- and we're still over a week away from the peak of the season. Eventually we'll quiet down, but we probably have another week left in this run.



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