[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 272043
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 PM AST FRI AUG 27 2010

THE CONVECTIVE CLOUD STRUCTURE OF DANIELLE HAS IMPROVED A LITTLE
DURING THE DAY AND THE 15-20 NMI DIAMETER EYE REMAINS VERY
DISTINCT. UPPER-LEVEL OUTFLOW IS GOOD IN ALL QUADRANTS AND
CONTINUES TO IMPROVE TO THE NORTH AND EAST OF THE HURRICANE. AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT INVESTIGATED DANIELLE EARLIER
THIS AFTERNOON AND FOUND A CENTRAL PRESSURE OF 942 MB AND MAXIMUM
700 MB FLIGHT-LEVEL WINDS OF 119 KT...WHICH EQUATES TO ABOUT 107 KT
SURFACE WINDS. MAXIMUM SFMR WINDS WERE ONLY 101 KT...HOWEVER.
SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB WERE A CONSENSUS
T6.0/115 KT. UW-CIMSS ADT ESTIMATES ARE T6.4/125 KT... AND HAVE
BEEN INCREASING OVER THE PAST COUPLE OF HOURS. A BLEND OF THESE
INTENSITY ESTIMATES SUPPORTS KEEPING THE INTENSITY AT 115 KT FOR
THIS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 310/08. THE NHC MODEL GUIDANCE
REMAINS TIGHTLY PACKED THROUGH 48-72 HOURS...AND IS STILL
INDICATING SHARP RECURVATURE BY 24 HOURS AROUND THE SUBTROPICAL
RIDGE THAT LIES ALONG 29N-30N LATITUDE. AFTER RECURVATURE
OCCURS...A STRONG MID-LEVEL TROUGH CURRENTLY PUSHING SOUTHEASTWARD
OFF THE EASTERN U.S. COAST AND CANADIAN MARITIMES REGION IS
FORECAST TO ACCELERATE DANIELLE QUICKLY TO THE NORTHEAST OR
EAST-NORTHEAST AND GRADUALLY CAPTURE THE CYCLONE AT HIGHER
LATITUDES BY 96 HOURS...AND THEN TURN IT SHARPLY POLEWARD BY 120
HOURS AS A STRONG AND DEEP EXTRATROPICAL CYCLONE. THE OFFICIAL
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK THROUGH 96
HOURS...AND THEN A MORE POLEWARD AT DAY 5...WHICH REMAINS
CONSISTENT WITH THE CONSENSUS MODELS...TVCN AND TVCC.

DANIELLE MAY STRENGTHEN SLIGHTLY DURING THE NEXT 12-24 HOURS AS THE
HURRICANE MOVES INTO A REGION OF LOWER VERTICAL SHEAR AND OVER 29C
SSTS. BY 36 HOURS...HOWEVER...INCREASING SOUTHWESTERLY VERTICAL
SHEAR AHEAD OF THE AFOREMENTIONED TROUGH SHOULD COMBINE WITH
DECREASING SSTS TO INITIATE STEADY WEAKENING. AROUND 96 HOURS OR
SO...DANIELLE SHOULD BEGIN EXTRATROPICAL TRANSITION AS IT MERGES
WITH A STRONG FRONTAL SYSTEM AND BE FULLY EXTRATROPICAL BY 120
HOURS AS A VERY LARGE 60-KT LOW PRESSURE SYSTEM OVER THE FAR NORTH
ATLANTIC. THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE VARIOUS
INTENSITY MODELS.

ALTHOUGH THE CENTER OF DANIELLE IS EXPECTED TO PASS WELL TO THE EAST
OF BERMUDA...THE LARGE AND EXPANDING WIND FIELD ON THE WEST SIDE OF
THE HURRICANE COULD BRING TROPICAL-STORM-FORCE WINDS CLOSE TO
BERMUDA ON SATURDAY. FOR THIS REASON...A TROPICAL STORM WATCH HAS
BEEN ISSUED FOR THAT ISLAND.

FORECAST POSITIONS AND MAX WINDS

INITIAL      27/2100Z 27.3N  60.3W   115 KT
 12HR VT     28/0600Z 28.6N  61.0W   120 KT
 24HR VT     28/1800Z 30.5N  60.8W   110 KT
 36HR VT     29/0600Z 32.8N  59.0W   100 KT
 48HR VT     29/1800Z 35.1N  56.3W    85 KT
 72HR VT     30/1800Z 38.4N  49.7W    75 KT
 96HR VT     31/1800Z 41.8N  39.1W    65 KT
120HR VT     01/1800Z 50.0N  28.0W    60 KT...POST-TROP/EXTRATROP

$$
FORECASTER STEWART


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