Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 7:45 PM GMT on June 01, 2009
UPDATE 8:15 EDT:
The NHC has recognized the system, but for some reason has not named it yet, despite clear evidence that the system meets STS criteria, and has met it for at least the 6-hour minimum that the NHC likes to see. They are inconsistent in this area so there is no way to know. The invest will not be able to maintain itself for much longer due to cold SSTs.
ABNT20 KNHC 012355
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON JUN 1 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
A NON-TROPICAL AREA OF LOW PRESSURE LOCATED A COUPLE HUNDRED MILES
NORTH-NORTHEAST OF THE AZORES ISLANDS IS PRODUCING WINDS TO NEAR
GALE FORCE. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE LOW HAVE
BECOME A LITTLE LESS ORGANIZED DURING THE PAST FEW HOURS. THIS
SYSTEM IS EXPECTED TO MOVE NORTHWARD OVER COOLER WATERS DURING THE
NEXT DAY OR TWO. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A SUBTROPICAL CYCLONE DURING THE NEXT 48
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
We got a surprise to start off the 2009 Atlantic Hurricane Season! The SSD just put up an "invest" floater on a 1002mb extratropical system in the NE Atlantic centered around 24W 40N, just north of the Azores. This system has become warm-secluded (part warm-core), as seen in the phase diagram and satellite image below:
You can see the sub-tropical characteristics associated with this system. Shallow thunderstorms have formed into symmetrical bands rotating inward towards a warm "eye" at the center of the system. QuikSCAT shows a well-defined secondary wind field at the center of the system with tropical storm-force winds. This system bears great resemblance as well as location to Hurricane Vince of the 2005 hurricane season, although Vince was fully tropical.
What precipitated this rare event was probably the system getting cut off from the main westerlies and becoming a closed upper low over the NE Atlantic with the frontal structures spread out quite far from the center of the storm. The system is over water temperatures less than 20C, and hence thunderstorm activity is shallow, but we've seen things like this happen before and we know that it is not impossible. The low will move slowly towards the north and then northeast during the next couple days before the GFS forecasts it to dissipate. This system, by all definition, deserves to be named Sub-tropical Storm Ana, but we'll see whether the NHC decides to be weird or not. Enjoy this awesome storm =)
We shall see what happens!
Visible Loop of the sub-tropical storm (click image for loop)
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