Sunday, August 07, 2005

Tropical Storm Irene


At  11AM EDT, the center of newly formed Tropical Storm Irene was at 20.5 North 45.5 West, 1160  miles of east of the northern leeward islands  and moving to the west-northwest at 9 mph.  Maximum sustained winds are 40 mph and minimum central pressure is 1005 millibars (29.68").

Upgrade to a tropical storm was based on a observations of 40 knots winds  from the Quikscat satellite.  Organization and covection have since diminished so the initial intensity was set at 35 knots.  When the motion of the system as a whole (i.e. when you ignore the disappear/reappear games the center of the storm has been playing), the average heading is 300 (west-northorthwest).  This motion is expected to continue until Irene finds an expected weakness in the high pressure ridge to her north and turns to the northwest.  While sea surface temperatures are increasing along Irene's path, upper level winds remain unfavorable for development.  Increases in the intensity forecast are reserved for the end of the period on the chance that shear decreases.  This is the earliest ninth tropical storm on record.  On average only two storms form by this point in the season.

Previous record for earliest ninth tropical storm was set on August 20, 1936. The next record (for the earliest tenth tropical storm) was set on August 23, 1995.

This was an annoying storm to track last night as the center disappeared for a few hours and then rappeareed to the north of its previouls location.  The system had played a similar game yesterday morning. 

Looking at the visible satellite loop,  the storm almost looked impressive (or at least the best it had ever looked) earlier this morning.  That appearance has since degraded, however, as the shear analysis shows that it has a hostile 20+ knots of shear to contend with.

Track forecast remains to my expectations.  The only chance for Irene to affect any kind of
land is to pass over Bermuda, and now it looks like she may not make it even that far west.  The situation in the atmosphere remains in  line with what was expected.  Also, the record of the past 55 years shows that no storms that were within 50 nautical miles of Irene's 11 AM position affected land.  (The only one to come close was a weak tropical storm that dissipated just north of the Windward Islands.  The present atmospheric situation clearly prevents such a path).   Like yesterday, it is not a question if the storm will turn to sea, only when.

2005 Hurricane Season, Weather comment []12:08:38 PM   trackback []