Wednesday, August 03, 2005



Tropics Watch 0803



The tropical wave I mentioned yestersday that is in the eastern Atlantic continues to look like a future tropical depression/storm. The Tropical Weather Outlook mentions it thusly:

THE COMBINATION OF A TROPICAL WAVE AND A LOW PRESSURE CENTER IS
PRODUCING A LARGE AREA OF DISTURBED WEATHER ABOUT 375 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS. THIS SYSTEM HAS THE
POTENTIAL FOR SOME DEVELOPMENT DURING THE NEXT DAY OR TWO AS IT
MOVES TOWARD THE WEST-NORTHWEST OVER THE EASTERN ATLANTIC.


I continue to think that we won't see anything really interesting out of this until it gets past 40° West (and on its current course it wouldn't be out there until Friday evening). However, there is already a closed circulation, so things could start happening sooner.

GFS, UKMET, and Canadian models continue to suggest that this will develop and move to the northwest and eventually to the north such that it would not threaten land.

However, the GFDL has a dissenting position. It keeps the wave on a more westerly course that would increase the probability of it affecting land at some point.

Due to how far out it is, we will have plenty of time to watch and wait.

SLIGHTLY LATER:  This Quickscat image shows what the winds are in the eastern Atlantic.  If you look along the 12° North line, between 28° and 30° West, you can see the tell-tale sign of a closed circulation: winds shifting in a counter-clockwise manner, forming a circle. 

Arguably, that image is enough to classify this as a tropical depression.


2005 Hurricane Season, Weather comment []7:42:10 PM   trackback [] 


Tropical Storm Harvey Update 031810Z



THE FIRST REPORTS FROM AN AIR FORCE RESERVE UNIT RECONNAISSANCE
AIRCRAFT INVESTIGATING TROPICAL STORM HARVEY INDICATE THAT HARVEY
IS STRONGER THAN PREVIOUSLY ESTIMATED. THE AIRCRAFT FOUND A
MINIMUM SEA-LEVEL PRESSURE OF 999 MB AND PEAK FLIGHT-LEVEL WINDS OF
62 KT. BASED ON THESE DATA...THE INTENSITY OF HARVEY IS NOW
ESTIMATED TO BE NEAR 60 MPH.

TD8 was upgraded to TS Harvey at 11 AM EDT today.   The intensity estimate was 40 mph.  As noted above, the intensity is significantly greater than estimated.  Part of the problem was disagreements over how to analyze the imagery; whether it should be treated as a tropical system or a sub-tropical system.

Needless to say, this throws all previous intensity forecasts out of whack.  The last intensity model forecast only brought the system up to 50 knots.  However, an important part of that inensity model is the current strength of the system (which is set by a human).  If the initial intensity isn't set correctly, then the model output isn't going to be accurate.

Otherwise, the forecast is in good shape.  No surprises as far as track goes.
  

2005 Hurricane Season, Weather comment []2:46:23 PM   trackback []