18 September 2009

Fred possibly making a comeback, new disturbance in central Atlantic...

Fred was initially classified as a Depression back on Sep 7, then was a major hurricane on Sep 9, dissipated on Sep 12, and after traveling 2000 miles westward as a low-level swirl, is finally making a convective comeback.  However, it won't be an easy path to regeneration... the vertical wind shear is quite strong from the north and expected to only relax slightly in the 1-2 day timeframe.  The SSTs under the storm will be ample to support a strong storm (28-29C) if the shear ends up being less than forecast.  A number of computer models intensify Fred over the next several days as it tracks fairly slowly to the WNW-NW.  The remnant circulation is located about 500 miles of Puerto Rico.

The other feature of interest is a slow-moving easterly wave that exited the African coast on Sep 10 and is now located near 13N 40W, or about 1400 miles east of the Windward Islands.  Similar to the remnants of Fred, the vertical shear is prohibitive for significant strengthening in the foreseeable future.  Some models do show it intensifying in the 4-5 day timeframe.  The next name on the list is Grace should it get named.

Please visit my tropical Atlantic headquarters.

08 September 2009

Fred forms in far eastern Atlantic...

On Monday afternoon, the easterly wave I referenced on Friday (was inland over western Africa then) was upgraded to Tropical Depression 7, and was further upgraded to Tropical Storm Fred just 6 hours later.  Since then, Fred has continued to get better organized and the latest intensity is 60kts and 990mb.  It is located about 350 miles southwest of the Cape Verde islands and tracking west at 12kts.

The satellite presentation is very impressive... there is healthy symmetric outflow, persistent cold cloud tops over the center, and microwave imagery reveals an eye and eyewall.  Fred is forecast to become the second hurricane of the season in the near future, and start heading NW into the open central Atlantic.  In the longer term, the same trough that will be responsible for steering Fred NW will also introduce a much less favorable environment and the storm should weaken notably by the end of the weekend.

Please visit my tropical Atlantic headquarters.

04 September 2009

Erika dissipates, new easterly wave developing...

Earlier today, NHC wrote their final advisory on Erika, which was downgraded to a Tropical Depression on Thursday.  In the face of strong mid-level wind shear, the low-level circulation was completely removed from the mid- and upper- level circulation and convection.  The remnant circulation is now south of Puerto Rico and will we monitored for any signs of redevelopment.

Elsewhere, a potent easterly wave is located just south of the Cape Verde islands and tracking W at 18kts.  There is a 1012mb Low associated with the wave.  On satellite imagery, it has an impressive presentation, both in the low-level circulation and attendant convection.
However, most computer models do not develop THIS wave, but rather the one behind it, currently over western Africa.

Please visit my tropical Atlantic headquarters.

01 September 2009

Erika finally forms in central Atlantic...

Since leaving the African coast one week ago, this easterly wave has remained intact, but struggled with shear.  Today, an aircraft reconnaissance flight revealed a closed circulation with 45kt sustained winds at the surface and a 1007mb central pressure.  So, it was immediately upgraded to TS Erika.  It's heading WNW at 8kts, and is located about 400 miles east of the Leeward Islands.  A Tropical Storm Watch has been issued for the northern Leeward Islands.

The official forecast is for gradual strengthening, but not quite reaching hurricane intensity, and to continue heading WNW.  By Friday, it should be just north of Puerto Rico... and in the longer term, this is a storm that the US east coast should be keeping an eye on.  A majority of forecast models bring Erika up to CAT1-2 intensity by the weekend.

Please visit my tropical Atlantic headquarters.