sub-Tropical storm Andrea

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sub-Tropical storm Andrea

Postby hurricane » Mon May 07, 2007 6:13 pm

[May 7, 6:13pm] As you no doubt noticed on the main page, there is a large low pressure area featured off the coast of South Carolina today causing significant wind in the north-east Florida area along with wind on much of the east coast.

Looking at the satellite pictures the system looks sub-tropical. However the system is in a low-shear zone and over relatively warm waters. Models indicate that it will move more south-westerly bringing it over even warmer models.

What does all that mean? Easy: it will probably remain non-tropical, but there is a chance that it could develop into Andrea. It is one of those, "wow that would be early, but not unheard of" events.

Consequently, the odds are against a tropical system forming, but stranger things have happened. See 2005 Atlantic hurricane season for example.

Care to place bets yourself? ;-)


[Editted to remove the uncertainty in the title]
Last edited by hurricane on Wed May 09, 2007 10:21 am, edited 2 times in total.

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Postby hurricane » Tue May 08, 2007 9:29 am

As of this morning the system has taken on more tropical characteristics (e.g. convection). It is somewhat surprising that the NHC has not taken official notice of this yet.

Notice the convection showing in this image:
http://www.goes.noaa.gov/GIFS/ECI7.JPG
and this image:
http://www.ssd.noaa.gov/goes/flt/t4/avn-l.jpg

:-)

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"Non tropical low" vs "Sub-tropical low"

Postby hurricane » Tue May 08, 2007 10:16 am

It appears the National Hurricane Center has taken some notice (see below), calling it a "non-tropical low" as of 9:50am. The Weather Channel is now (11am) stating it is a "sub-tropical low" so there seems to be a significant amount of confusion regarding the system. Other forecasters are noting the tropical characteristics (see http://www.thestormtrack.com/2007/05/pr ... _storm.php) as well.

The summary:
Suffice it to say that the low -everyone agrees it is a low- has gale force winds (32-63 mph), probably around 50 mph. Everyone one the southeast coast should monitor the system whatever the classification.


----

SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
950 AM EDT TUE MAY 8 2007

A NON-TROPICAL LOW PRESSURE SYSTEM...CENTERED ABOUT 230 MILES
EAST-SOUTHEAST OF THE GEORGIA AND SOUTH CAROLINA COASTS...HAS BEEN
MOVING SLOWLY WESTWARD AT 5 TO 10 MPH. THIS SYSTEM IS PRODUCING
GALE-FORCE WINDS AND HEAVY SURF ALONG THE COASTS OF NORTH
CAROLINA...SOUTH CAROLINA...AND GEORGIA...WITH STRONGER WINDS
OFFSHORE. ASSOCIATED SHOWER ACTIVITY HAS INCREASED SINCE
YESTERDAY...BUT NO SIGNIFICANT STRENGTHENING OF THIS SYSTEM IS
EXPECTED. THE LOW IS BEING MONITORED FOR SIGNS OF TROPICAL OR
SUBTROPICAL CYCLONE DEVELOPMENT...AND AN AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT WILL BE AVAILABLE TO INVESTIGATE THE SYSTEM
TOMORROW MORNING...IF NECESSARY.

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Postby hurricane » Wed May 09, 2007 9:30 am

And then we have today word that the NHC may begin for Subtropical Storm Andrea will begin later today...

WONT41 KNHC 091303
DSAAT
SPECIAL TROPICAL DISTURBANCE STATEMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
905 AM EDT WED MAY 9 2007

SATELLITE IMAGERY AND PRELIMINARY REPORTS FROM AN AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT THIS MORNING INDICATE THAT THE AREA OF LOW
PRESSURE CENTERED ABOUT 150 MILES EAST OF JACKSONVILLE IS ACQUIRING
THE CHARACTERISTICS OF A SUBTROPICAL CYCLONE. THE SYSTEM CONTINUES
MOVING GENERALLY WESTWARD AT ABOUT 5 MPH. IF PRESENT TRENDS
CONTINUE... ADVISORIES ON SUBTROPICAL STORM ANDREA WOULD BE
INITIATED LATER THIS MORNING.

DANGEROUS SURF CONDITIONS CONTINUE ALONG THE COASTS OF THE
CAROLINAS... GEORGIA... AND NORTHEASTERN FLORIDA. INTERESTS IN
THESE AREAS SHOULD CONTINUE TO MONITOR PRODUCTS ISSUED BY LOCAL
NATIONAL WEATHER SERVICE FORECAST OFFICES. ADDITIONAL INFORMATION
ON THIS SYSTEM CAN ALSO BE FOUND IN HIGH SEAS FORECASTS ISSUED BY
THE NATIONAL WEATHER SERVICE... UNDER AWIPS HEADER NFDHSFAT1 AND
WMO HEADER FZNT01 KWBC.

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Andrea

Postby hurricane » Wed May 09, 2007 10:18 am

The NHC began advisories on Sub-Tropical Storm Andrea at 11am today, May 9. In my book 24-36 hours late, but it was a judgement call and perhaps the NHC was hoping it would fall apart without needlessly getting people stirred-up about the low.


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