WTNT43 KNHC 152049
TCDAT3
 
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
500 PM EDT WED AUG 15 2012
 
THE LOW PRESSURE SYSTEM THAT HAS BEEN MOVING ACROSS THE EASTERN AND
CENTRAL ATLANTIC OCEAN FOR THE PAST WEEK HAS FINALLY ACQUIRED
ENOUGH PERSISTENT ORGANIZED CONVECTION TO BE CLASSIFIED AS A
TROPICAL DEPRESSION. ALTHOUGH CLOUD TOPS ARE NOT PARTICULARLY
COLD...THE CONVECTION IS DEEP ENOUGH TO MEET THE CRITERIA FOR
DVORAK SATELLITE CLASSIFICATIONS...WHICH ARE T1.5/25 KT FROM TAFB
AND SAB. HOWEVER...CONVECTIVE BANDING HAS IMPROVED SINCE THE 18Z
CLASSIFICATIONS. ALSO...A RECENT UW-CIMSS SATELLITE INTENSITY
ESTIMATE INDICATES THE INTENSITY IS NEAR 30 KT...AND THAT IS THE
INTENSITY USED FOR THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 355/16 KT BASED ON A BLEND OF VISIBLE
AND MICROWAVE SATELLITE FIXES OVER THE PAST 12 HOURS. THE NHC MODEL
GUIDANCE IS IN EXCELLENT AGREEMENT ON THE CYCLONE MOVING NORTHWARD
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE FOR THE NEXT
12 HOURS OR SO. AFTER THAT...A SHARP TURN TOWARD THE NORTHEAST AND
EVENTUALLY TOWARD THE EAST IS EXPECTED AS THE CYCLONE BECOMES
EMBEDDED IN THE DEEP-LAYER MID-LATITUDE WESTERLIES ACROSS THE NORTH
ATLANTIC. BY DAYS 4 AND 5...THE CYCLONE IS FORECAST TO BECOME
CAPTURED BY A SHORTWAVE TROUGH AND LIFT OUT TO THE NORTHEAST
TOWARD THE AZORES ISLANDS. THE OFFICIAL TRACK FORECAST CLOSELY
FOLLOWS THE CONSENSUS MODELS TVCA AND TV15.
 
THE DEPRESSION HAS A RELATIVELY SMALL CIRCULATION THAT IS SURROUNDED
BY VERY DRY MID-LEVEL AIR. ALTHOUGH THE CYCLONE WILL REMAIN OVER
FAVORABLE SEA-SURFACE TEMPERATURES FOR THE NEXT 2-3 DAYS AND IN A
LOW VERTICAL SHEAR ENVIRONMENT...OCCASIONAL INTRUSIONS OF DRY AIR
ARE EXPECTED TO KEEP THE SYSTEM CONVECTIVELY CHALLENGED THROUGHOUT
THE FORECAST PERIOD. ALTHOUGH NOT EXPLICITLY FORECAST...THE BEST
OPPORTUNITY FOR THE CYCLONE TO ACHIEVE HURRICANE STATUS WOULD BE
BETWEEN 48 AND 72 HOURS PRIOR TO THE ONSET OF STRONG WESTERLY
VERTICAL WIND SHEAR ON DAY 3. THE OFFICIAL INTENSITY FORECAST IS
BELOW THE MAJORITY OF THE GUIDANCE DUE TO THE POTENTIALLY NEGATIVE
EFFECTS OF THE SURROUNDING DRY ENVIRONMENT...BUT ABOVE THE GFDL
WHICH SHOWS LITTLE STRENGTHENING.
 
THIS SYSTEM IS EXPECTED TO REMAIN WELL TO THE EAST OF BERMUDA AND...
THEREFORE...SHOULD NOT HAVE ANY DIRECT IMPACT ON THAT ISLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/2100Z 29.9N  55.1W   30 KT  35 MPH
 12H  16/0600Z 31.6N  55.0W   35 KT  40 MPH
 24H  16/1800Z 33.5N  53.4W   40 KT  45 MPH
 36H  17/0600Z 34.6N  50.4W   45 KT  50 MPH
 48H  17/1800Z 35.0N  46.5W   50 KT  60 MPH
 72H  18/1800Z 35.2N  38.3W   60 KT  70 MPH
 96H  19/1800Z 36.6N  29.7W   60 KT  70 MPH
120H  20/1800Z 38.8N  23.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT43 KNHC 160242
TCDAT3
 
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
1100 PM AST WED AUG 15 2012
 
ALTHOUGH THE CONVECTION IS NOT VERY DEEP...THE OVERALL CLOUD
PATTERN...WHICH IN FACT IS SMALL...IS A LITTLE BETTER ORGANIZED
THAN EARLIER TODAY. A CYCLONICALLY-CURVED BAND IS WRAPPING AROUND
THE NORTHERN HALF OF THE SYSTEM...BUT THE UPPER-LEVEL OUTFLOW IS
VERY LIMITED. T-NUMBERS FROM TAFB AND SAB HAVE INCREASED TO 2.0 ON
THE DVORAK SCALE WHICH RESULTS IN AN INITIAL INTENSITY OF 30 KNOTS.
THE DEPRESSION HAS THE OPPORTUNITY TO STRENGTHEN DURING THE NEXT 2
TO 3 DAYS BEFORE THE SHEAR INCREASES AND THE CYCLONE ENCOUNTERS
COOLER WATERS. ON THIS BASIS...THE NHC FORECAST SHOWS ONLY A SLIGHT
INTENSIFICATION DURING THE NEXT 2 TO 3 DAYS FOLLOWING THE ICON AND
THE LGEM MODELS...BUT NOT AS MUCH AS THE HWRF...WHICH INSISTS ON
MAKING THE DEPRESSION A HURRICANE IN ABOUT 36 HOURS OR SO. 

THE DEPRESSION IS MOVING TOWARD THE NORTH-NORTHWEST OR 345 DEGREES
AT 15 KNOTS AROUND THE WESTERN EDGE OF THE SUBTROPICAL HIGH. VERY
SOON...THE CYCLONE WILL LIKELY SLOW DOWN AND RECURVE AS IT BECOMES
EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES. ONCE IN THE
WESTERLIES...THE CYCLONE SHOULD TURN EASTWARD WITH SOME INCREASE IN
FORWARD SPEED. THERE IS HIGH CONFIDENCE IN THE FIRST PORTION OF THE
FORECAST SINCE MOST OF THE TRACK MODELS ARE IN VERY GOOD
AGREEMENT...AT LEAST DURING THE NEXT 3 DAYS. AFTER THAT...THE
FORECAST IS LESS CERTAIN...BUT IT APPEARS THAT IN 4 DAYS OR
SO...THE CYCLONE WILL BE MOVING VERY NEAR THE AZORES. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0300Z 31.3N  55.5W   30 KT  35 MPH
 12H  16/1200Z 33.0N  54.4W   35 KT  40 MPH
 24H  17/0000Z 34.5N  52.0W   40 KT  45 MPH
 36H  17/1200Z 35.5N  48.3W   50 KT  60 MPH
 48H  18/0000Z 35.5N  44.5W   60 KT  70 MPH
 72H  19/0000Z 35.5N  36.0W   60 KT  70 MPH
 96H  20/0000Z 37.5N  28.0W   55 KT  65 MPH
120H  21/0000Z 40.0N  22.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

