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Subtropical Depression ELEVEN (Text)

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SUBTROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112007
500 AM EDT SUN SEP 23 2007
 
THE NON-TROPICAL LOW PRESSURE SYSTEM THAT HAS BEEN MEANDERING OVER
THE NORTH CENTRAL ATLANTIC DURING THE PAST FEW DAYS HAS BEEN
PRODUCING SOME PERSISTENT DEEP CONVECTION DURING THE LAST 12 HOURS
OR SO.  THAT CONVECTION HAD INITIALLY BEEN LIMITED TO THE WESTERN
SEMICIRCLE...BUT HAS BEEN STEADILY WRAPPING AROUND THE
SOUTHERN SEMICIRCLE OVERNIGHT.  VERY RECENTLY THE CONVECTION HAS
ALSO INCREASED TO THE EAST OF THE CIRCULATION CENTER...WHERE SOME
LONG-RANGE LIGHTNING SIGNATURES HAVE EVEN BEEN DETECTED.  TAFB
PROVIDED A TROPICAL DVORAK T-NUMBER OF 2.0...WHILE THE SAB
CLASSIFICATION WAS SUBTROPICAL 2.5.  THE CYCLONE FELL IN THE GAP
BETWEEN QUIKSCAT PASSES ABOUT 12 HOURS AGO...AND DATA FROM A NEW
OVERPASS HAS NOT YET ARRIVED.  THE INITIAL INTENSITY IS SET TO 30
KT.  THE SYSTEM IS DESIGNATED SUBTROPICAL FOR NOW...GIVEN THAT IT
IS STILL WELL-INVOLVED WITH AN UPPER-LEVEL LOW...AND SINCE THE
CONVECTION IS STILL A BIT DISTANT FROM THE CENTER.  THE RECENT
TRENDS IN SATELLITE IMAGERY...HOWEVER...SUGGEST THE SYSTEM IS
GRADUALLY GAINING MORE TROPICAL CHARACTERISTICS AND SHOULD BECOME A
TROPICAL CYCLONE LATER TODAY.

THE DEPRESSION HAS REMAINED STATIONARY FOR THE PAST SEVERAL
HOURS...TRAPPED WITHIN A LARGE MID- TO UPPER-LEVEL CUTOFF LOW. 
ALL AVAILABLE MODEL GUIDANCE INDICATES THIS WILL CHANGE
SOON...HOWEVER...AS A LARGE EXTRATROPICAL SYSTEM MOVES EASTWARD
OVER ATLANTIC CANADA DURING THE NEXT 24 HOURS.  THAT LARGER SYSTEM
WILL PULL THE DEPRESSION NORTHWARD AND EVENTUALLY ABSORB IT WITHIN
THE NEXT COUPLE OF DAYS.  THE OFFICIAL FORECAST RELIES ON MODEL
GUIDANCE THAT IS IN VERY GOOD AGREEMENT ON THIS SCENARIO...AND
CALLS FOR THE SYSTEM TO BE ABSORBED IN 48 HOURS OR LESS.  DURING
THE NEXT 24 HOURS...THERE IS SOME OPPORTUNITY FOR A LITTLE
STRENGTHENING OVER SSTS NEAR 24 CELSIUS...AND THE OFFICIAL FORECAST
CALLS FOR THE CYCLONE TO REACH 40 KT BEFORE TRAVERSING COOLER
WATERS AND BECOMING EXTRATROPICAL.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 36.2N  46.1W    30 KT
 12HR VT     23/1800Z 36.7N  46.1W    35 KT...TROPICAL
 24HR VT     24/0600Z 38.7N  45.3W    40 KT...TROPICAL
 36HR VT     24/1800Z 42.5N  42.5W    40 KT...BECOMING EXTRATROPICAL
 48HR VT     25/0600Z...ABSORBED BY LARGER EXTRATROPICAL SYSTEM
 
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FORECASTER KNABB
 
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