TAOI 07-20-2010

There are 2 primary areas of interest within the experiment domain, PGI-16L and AL-97 (PGI-17L).  PGI-16L is centered east of the Yucatan Peninsula around 20N, 85W.  AL-97 is located north of Puerto Rico,  just SW of 20N,65W.  Elsewhere in the Atlantic, a pair of 1025 and 1027 hPa ridges dominates the flow resulting in largely easterly surface winds from Africa through Gulf of Mexico.  The NHC is analyzing a tropical wave in the SW Gulf of Mexico, west of 90W, however this has no PGI assignment.  This wave is associated with an upper-level low in the central Gulf, and convection is observed in this location.  While it poses no development threat, it will bring rain and thunderstorms to the eastern Texas coast within the next 2 days.  Another upper-level low remains north of AL-97, and is contributing to high shear just north of AL-97's center.  However, the center itself is in an area of relatively low shear, only 5-10 kts.  However, there is a strong shear gradient here.  Shear is low through the Gulf of Mexico and Southern Caribbean.  Finally, PGI-18L is located near 13N,30W, however pouch tracking shows no immediate threat of development.

Over the past 24 hours, PGI-16L has remained relatively unorganized, however convection has remained fairly persistent.   Satellite imagery shows a slight hint of a mid-level circulation, but no surface circulation has been observed on ASCAT.  While NOGAPS has no pouch in the 00Z run, the GFS has PGI-16L crossing the Yucatan Peninsula within the next 12 hours before losing the pouch over the SW gulf after the 36 hour forecast.

AL-97L continues to be the primary area of interest.  The NHC has a 40% probability of development within the next 48 hours as of 12Z.  Over the past 24 hours, convection has become somewhat more concentrated towards the center of the pouch.  However, a clear low level circulation is still not evident from ASCAT, however the most recent passes have not had complete coverage over the area.  Additionally, while the center is in an environment of low shear, there is a strong shear gradient just to the north.  Depending on the exact track of AL-97, it could move into a region of shear greater than 30kts, or remain in an area of 20 or fewer knots.  A consensus of 12Z models seem to favor a relatively more northern track, which would bring AL-97 into the Bahamas within the next 48 hours, and approaching the southern (east) coast of Florida within 90 hours.  This track would keep the system in high shear for the immediate future and would suppress any development.

GFS and NOGAPS pouch tracking are somewhat conflicting.  While the GFS has the center moving north through higher shear, it actually develops AL-97 fairly quickly resulting in OW and Zeta values literally off the chart.  On the other hand, NOGAPS develops the system very little over the next 120 hours while shear remains relatively low due to a more southerly predicted path.  A consensus model intensity forecast would be the development of a tropical storm within the next 36-48 hours, however due to the lack of a defined surface circulation, and the expected track through an area of high shear, I don't expect much development within the next 48 hours unless a circulation does develop