[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 300250
TCDAT1
HURRICANE DANIELLE DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
1100 PM AST SUN AUG 29 2010

DEEP CONVECTION HAS GRADUALLY ERODED INTO AN ELONGATED BAND IN THE
NORTHERN SEMICIRCLE AS DANIELLE CONTINUES TO MOVE OVER COOLER WATER
AND TAKES ON THE APPEARANCE OF AN EXTRATROPICAL CYCLONE. HOWEVER...
A UW-CIMSS AMSU INTENSITY ESTIMATE AT 29/2133 UTC STILL INDICATED
A STRONG UPPER-LEVEL WARM CORE...AN INTENSITY ESTIMATE OF 87 KT AND
A PRESSURE OF 968 MB.  THE INITIAL INTENSITY OF 70 KT IS A BLEND OF
THE AMSU ESTIMATE AND A DVORAK CURRENT INTENSITY ESTIMATE OF
T4.0/65 KT FROM TAFB.

DANIELLE APPEARS TO HAVE SLOWED DOWN SOME DURING THE PAST 6 HOURS
AND THE MOTION ESTIMATE IS 045/14. WATER VAPOR IMAGERY INDICATES
THAT DANIELLE HAS CLEARLY BEEN CAPTURED BY A LARGE MID-/UPPER-LEVEL
TROUGH AND THE FLOW PATTERN IS EVOLVING INTO A LARGE MID-LATITUDE
CUT-OFF LOW PRESSURE SYSTEM WHICH TYPICALLY MOVES SLOWER THAN A
TROPICAL CYCLONE AT THIS LATITUDE. THE GLOBAL MODELS ARE IN FAIR
AGREEMENT ON DANIELLE MOVING NORTHEASTWARD OR EVEN EAST-
NORTHEASTWARD AT 15-20 KT FOR THE NEXT 2 DAYS OR SO...FOLLOWED BY
ACCELERATION TOWARD THE NORTH-NORTHEAST AND THEN NORTHWARD BY DAYS
3 AND 4 AS A LARGER AND STRONGER MID-/UPPER-LEVEL TROUGH MOVES OUT
OF NORTHEASTERN CANADA AND ACTS TO KICK OUT THE EXTRATROPICAL
DANIELLE CIRCULATION. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY THROUGH 48 HOURS AND IS A BLEND OF THE PREVIOUS
TRACK AND THE CONSENSUS MODEL...TVCN...AFTER THAT.

DANIELLE IS EXPECTED TO CONTINUE TO WEAKEN AND BECOME FULLY
EXTRATROPICAL WITHIN THE NEXT 24 HOURS AS THE HURRICANE MOVES OVER
MUCH COOLER WATER THAT LIES NORTH OF 40N LATITUDE. HOWEVER...THE
CYCLONE IS EXPECTED TO GET A SHOT OF BAROCLINIC ENERGY BY 72 HOURS
FROM THE LARGER MID-/UPPER-LEVEL TROUGH COMING OUT OF CANADA...
WHICH WILL HELP THE EX-DANIELLE CIRCULATION REMAIN LARGE AND FAIRLY
STRONG OVER THE FAR NORTH ATLANTIC SHIPPING LANES.

THE 34-KT WIND RADII REMAIN LARGE AND ARE UNCHANGED BASED ON LIMITED
SHIP AND BUOY OBSERVATIONS SURROUNDING THE HURRICANE. 12-FT SEAS
RADII WERE SIGNIFICANTLY EXPANDED IN THE SOUTHWESTERN QUADRANT
BASED ON GUIDANCE FROM TAFB AND THE OCEAN PREDICTION CENTER.


FORECAST POSITIONS AND MAX WINDS

INITIAL      30/0300Z 39.3N  53.0W    70 KT
 12HR VT     30/1200Z 40.8N  51.2W    60 KT
 24HR VT     31/0000Z 42.0N  47.4W    55 KT...POST-TROP/EXTRATROP
 36HR VT     31/1200Z 43.5N  42.0W    55 KT...POST-TROP/EXTRATROP
 48HR VT     01/0000Z 45.1N  34.0W    60 KT...POST-TROP/EXTRATROP
 72HR VT     02/0000Z 51.5N  27.5W    60 KT...POST-TROP/EXTRATROP
 96HR VT     03/0000Z 60.0N  30.0W    50 KT...POST-TROP/EXTRATROP
120HR VT     04/0000Z...DISSIPATED

$$
FORECASTER STEWART


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