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Subtropical Depression TWENTY-TWO (Text)

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SUBTROPICAL DEPRESSION TWENTY-TWO DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SAT OCT 08 2005
 
SATELLITE IMAGERY THIS MORNING INDICATES THAT THE NON-TROPICAL LOW
PRESSIRE AREA SOUTHEAST OF BERMUDA HAS ACQUIRED SUFFICIENT
ORGANIZED CONVECTION TO BE CALLED A SUBTROPICAL DEPRESSION...
SUBTROPICAL INSTEAD OF TROPICAL DUE TO THE INTERACTION WITH A
LARGE-MID/UPPER LEVEL LOW SOUTH OF THE CYCLONE.  THE CENTER IS
LOCATED ON THE SOUTHEASTERN EDGE OF A CENTRAL CONVECTIVE FEATURE...
WITH AN ELONGATED OUTER BAND IN THE NORTHEASTERN SEMICIRCLE.
SATELLITE INTENSITY ESTIMATES ARE 25-30 KT FROM TAFB AND 35-40 KT
FROM SAB.  THE INITIAL INTENSITY OF 30 KT IS A BLEND OF THESE.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 320/13...UNCERTAIN
BECAUSE WHILE THE OVERNIGHT MOTION WAS NORTH-NORTHWESTWARD THE LAST
FEW IMAGES SUGGEST A TURN TOWARD THE LEFT.  IN THE SHORT TERM...THE
CYCLONE SHOULD MOVES GENERALLY WEST-NORTHWESTWARD BETWEEN A LARGE
DEEP-LAYER RIDGE TO THE NORTH AND THE LARGE MID/UPPER-LEVEL LOW TO
THE SOUTH.  AFTER 48 HR OR SO...THE TRACK FORECAST BECOMES LOW
CONFIDENCE AS A SIGNIFICANT SPREAD APPEARS IN THE GUIDANCE.  IF THE
LARGE-SCALE MODELS ARE RIGHT...A SECOND LOW PRESSURE AREA WILL FORM
TO THE SOUTH AND SOUTHEAST OF THE SUBTROPICAL DEPRESSION...WHICH
COULD STEER THE SYSTEM MORE WESTWARD.  ON THE OTHER HAND...IF THE
NEW LOW IS SLOWER TO FORM OR TROUGHING CONTINUES ALONG THE EAST
COAST OF THE UNITED STATES AS SUGGESTED BY THE LARGE-SCALE
MODELS...THE CYCLONE COULD TURN MORE TOWARD THE NORTH.  THE TRACK
FORECAST AFTER 48 HR WILL CALL FOR A GRADUAL NORTHWARD TURN AT A
DECREASING FORWARD SPEED ON THE PREMISE THAT THE MID/UPPER-LEVEL
TROUGHING WILL BE THE DOMINANT STEERING MECHANISM.
 
THE DEPRESSION IS CURRENTLY IN DEEP-LAYER EASTERLY FLOW ON THE NORTH
SIDE OF THE MID/UPPER-LEVEL LOW WITH ABOUT 10 KT OF SHEAR.  THE
SHIPS MODEL SUGGESTS THAT THE SYSTEM WILL UNDERGO SOME PULSES OF
SHEAR DURING THE NEXT THREE DAYS...AND THEN UNDERGO SIGNIFICANT
SHEAR AFTER THREE DAYS.  THE GFDL AND THE LARGE-SCALE MODELS ALL
LOSE THE SYSTEM IN 36-72 HR.  ALL OF THIS...COMBINED WITH SEA
SURFACE TEMPERATURES OF 26C-27C ALONG THE FORECAST TRACK...SUGGEST
THE CYCLONE COULD STRUGGLE TO INTENSIFY.  THE INTENSITY FORECAST
CALLS FOR MODEST STRENGTHENING IN LINE WITH THE SHIPS MODEL...WITH
A PEAK INTENSITY OF 50 KT IN 48 KT.  IF THE LARGE-SCALE MODELS ARE
CORRECT ON THE FORMATION OF THE SECOND LOW...OR IF THE SHIPS MODEL
IS CORRECT ABOUT THE SHEAR...THE CYCLONE COULD WEAKEN FASTER THAN
CURRENTLY FORECAST AFTER 72 HR.  THERE IS A CHANCE THE CYCLONE
COULD FULLY TRANSITION TO A TROPICAL CYCLONE DURING THE NEXT 48 HR.
 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 28.1N  59.0W    30 KT
 12HR VT     09/0000Z 29.2N  60.7W    35 KT
 24HR VT     09/1200Z 30.4N  63.4W    40 KT
 36HR VT     10/0000Z 31.2N  66.4W    45 KT
 48HR VT     10/1200Z 32.3N  68.3W    50 KT
 72HR VT     11/1200Z 34.0N  71.5W    50 KT
 96HR VT     12/1200Z 36.0N  72.0W    45 KT
120HR VT     13/1200Z 37.0N  72.0W    40 KT
 
 
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