WTNT44 KNHC 050236
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092009
1100 PM AST SUN OCT 04 2009
 
CONVECTIVE ACTIVITY ASSOCIATED WITH THE LOW PRESSURE AREA NORTHEAST
OF THE AZORES ISLANDS HAS BECOME BETTER ORGANIZED THIS EVENING. THE
CONVECTION...WHICH HAS SHOWN SOME ORGANIZATION FOR MUCH OF THE
DAY...IS RELATIVELY DEEP AND SURROUNDS AN EYE-LIKE FEATURE THAT HAS
PERSISTED FOR SEVERAL HOURS.  THIS IS THE SAME SURFACE LOW PRESSURE
AREA THAT MOVED THROUGH THE AZORES SEVERAL DAYS AGO AND MADE A
COUNTER-CLOCKWISE LOOP. THE LOW...PREVIOUSLY ASSOCIATED WITH AN
OCCLUDED FRONT AND CO-LOCATED WITH AN UPPER LOW...HAS SINCE LOST
ITS FRONTAL STRUCTURE AND IS NOW LOCATED UNDER A FAIRLY UNIFORM
SOUTHWESTERLY UPPER FLOW. IN ADDITION...2210Z ASCAT DATA INDICATED A
VERY SMALL RADIUS OF MAXIMUM WIND...LESS THAN 20 MILES. WITH THESE
STRUCTURAL CHANGES...THE SYSTEM CAN NOW BE CLASSIFIED AS A TROPICAL
STORM.
 
THE ASCAT PASS SHOWED A COUPLE OF 45-50 KT WIND VECTORS TO THE
SOUTHEAST OF THE CENTER...AND THESE DATA ARE THE BASIS FOR THE 55
KT INITIAL INTENSITY. GRACE IS CURRENTLY OVER SSTS AROUND 21
DEGREES CELSIUS AND WITHIN AN UPPER-LEVEL ENVIRONMENT CHARACTERIZED
BY LIGHT TO MODERATE SOUTHWESTERLY SHEAR. ALTHOUGH THE SHEAR IS NOT
FORECAST TO INCREASE DURING THE NEXT DAY OR TWO...THE CYCLONE IS
HEADED FOR EVEN COLDER WATER AND WILL LIKELY BEGIN TO WEAKEN VERY
SOON. THE GLOBAL MODELS SUGGEST THAT THE SMALL CYCLONE WILL BE
ABSORBED BY A LARGER EXTRATROPICAL CYCLONE OVER THE NORTHEASTERN
ATLANTIC IN ABOUT 36 HOURS...IF NOT SOONER.
 
GRACE IS MOVING NORTHEASTWARD IN THE DEEP LAYER SOUTHWESTERLY FLOW
OVER THE NORTHEASTERN ATLANTIC.  A GENERAL NORTHEASTWARD MOTION IS
EXPECTED TO CONTINUE UNTIL DISSIPATION.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0300Z 41.2N  20.3W    55 KT
 12HR VT     05/1200Z 44.0N  18.0W    50 KT
 24HR VT     06/0000Z 48.0N  16.0W    45 KT
 36HR VT     06/1200Z...DISSIPATED
 
$$
FORECASTER BROWN/FRANKLIN
 

WTNT44 KNHC 050851
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092009
500 AM AST MON OCT 05 2009
 
DESPITE ITS ENVIRONMENT AND UNUSUAL LOCATION...INFRARED SATELLITE
IMAGERY INDICATES THAT GRACE HAS BEEN MAINTAINING A SMALL BUT
IMPRESSIVE INNER CORE OF RELATIVELY DEEP CONVECTION. MORE
RECENTLY...THERE HAS BEEN AN EXPANSION OF COLD-TOPPED CONVECTION IN
A RING SURROUNDING A RAGGED EYE-TYPE FEATURE. BASED ON SUBJECTIVE
DVORAK CLASSIFICATIONS AND THE CURRENT TREND OF INCREASING
ORGANIZATION...THE INITIAL INTENSITY IS RAISED TO 60 KT. IT IS
UNCLEAR WHETHER SURFACE WINDS MATCH THE SATELLITE SIGNATURE...
ESPECIALLY SINCE CONVECTIVE TOPS MIGHT LACK SOME VIGOR OVER 20C
SSTS. HOWEVER...THERE HAVE BEEN NO RECENT DATA TO CONFIRM OR DENY
DVORAK ESTIMATES...OTHER THAN AN ASCAT PASS OF 45-50 KT FROM MUCH
EARLIER.
 
RECENT FIXES INDICATE THAT GRACE HAS ACCELERATED WHILE MOVING A
LITTLE TO THE LEFT OF ITS PREVIOUS HEADING AND IS NOW MOVING
045/24.  THE CYCLONE IS MOVING NORTHEASTWARD IN A DEEP LAYER OF
SOUTHWESTERLY FLOW...BUT IS EXPECTED TO TURN NORTH-NORTHEAST AND
DECELERATE AS A POTENT SHORTWAVE NEARS IT FROM THE SOUTHWEST. ON
THIS TRACK...A STEADY WEAKENING IS FORECAST AS GRACE MOVES OVER
SUB-20C WATER TEMPERATURES IN AN ENVIRONMENT OF MODERATE TO STRONG
WESTERLY SHEAR. GRACE SHOULD MERGE WITH A LARGER EXTRATROPICAL
CYCLONE OR ITS ASSOCIATED COLD FRONT OVER THE NORTHEAST ATLANTIC
WITHIN 24 TO 36 HOURS...IF NOT SOONER.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0900Z 43.0N  18.0W    60 KT
 12HR VT     05/1800Z 45.5N  16.5W    50 KT
 24HR VT     06/0600Z 49.0N  15.0W    45 KT
 36HR VT     06/1800Z...DISSIPATED
 
$$
FORECASTER KIMBERLAIN
 

WTNT44 KNHC 051445
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092009
1100 AM AST MON OCT 05 2009
 
THE CONVECTIVE STRUCTURE OF GRACE HAS BEGUN TO DETERIORATE
SLIGHTLY...WITH THE RING OF DEEP CONVECTION AROUND THE CENTER
BECOMING LESS SYMMETRIC AND FRACTURED.  THE INITIAL INTENSITY IS
LOWERED TO 55 KT ON THIS ADVISORY BASED ON TROPICAL AND SUBTROPICAL
CLASSIFICATIONS OF 3.5...AND A 0644 UTC QUIKSCAT PASS WHICH
SUPPORTED MAXIMUM WINDS BETWEEN 50 AND 55 KT.  ALSO...GRACE IS NOW
OVER WATER NEAR 18C...AND THIS IS LIKELY INHIBITING STRONG
CONVECTIVE MIXING OF WINDS TO THE SURFACE.  SOME ADDITIONAL
WEAKENING IS ANTICIPATED OVER THE NEXT 24 HOURS...AND THE GLOBAL
MODELS ALL INDICATE THAT GRACE SHOULD BE ABSORBED BY A FRONT JUST
SOUTHWEST OF IRELAND BY TUESDAY MORNING.
 
GRACE IS ACCELERATING WITH AN INITIAL MOTION OF 30 DEGREES AT 27 KT.
THE CYCLONE IS EXPECTED TO TURN TOWARD THE NORTH-NORTHEAST AND SLOW
DOWN OVER THE NEXT 12 TO 24 HOURS AS IT MOVES NORTH OF THE STRONGEST
BELT OF MID-LATITUDE WESTERLIES...AND BECOMES ABSORBED BY THE
FRONTAL BOUNDARY TO ITS NORTHWEST.
 
DESPITE THE FACT THAT GRACE IS MOVING OVER VERY COLD WATERS...AN
AMSU PASS FROM EARLIER TODAY STILL SHOWS THE PRESENCE OF A MODERATE
TO DEEP WARM CORE IN ASSOCIATION WITH THE CYCLONE.  IN ADDITION...
THE WIND RADII HAVE BEEN ADJUSTED BASED ON THE 0644 UTC QUIKSCAT
PASS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/1500Z 45.4N  16.4W    55 KT
 12HR VT     06/0000Z 48.0N  14.6W    50 KT
 24HR VT     06/1200Z...ABSORBED BY A FRONT
 
$$
FORECASTER BERG
 

WTNT44 KNHC 052034
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092009
500 PM AST MON OCT 05 2009
 
GRACE CONTINUES TO HAVE THE SATELLITE APPEARANCE OF A TROPICAL
CYCLONE AND A MODERATE TO DEEP WARM CORE AS INDICATED BY RECENT
AMSU PASSES.  HOWEVER...CLOUD TOP TEMPERATURES HAVE CONTINUED TO
WARM OVER THE PAST FEW HOURS AS THE CYCLONE IS NOW OVER SSTS OF
17-18C. THE INTENSITY IS DECREASED TO 50 KT BASED A SUBTROPICAL
CLASSIFICATION OF 3.5 FROM TAFB AND A DVORAK CI-NUMBER OF 3.0 FROM
SAB. A QUIKSCAT PASS SHOULD PROVIDE SOME INFORMATION ON THE
INTENSITY AND STRUCTURE OF GRACE SOON. THE CENTRAL PRESSURE IS HELD
AT 990 MB BASED ON AN 1800 UTC OBSERVATION OF 992 MB AND A WIND OF
20 KT FROM SHIP A8I02 ABOUT 30 NM NORTH OF THE CENTER OF GRACE.
 
THE INITIAL MOTION ESTIMATE IS 025/26 KT...AS GRACE IS BEING STEERED
BY DEEP-LAYER SOUTHWESTERLY FLOW AHEAD OF A MID- TO UPPER-LEVEL
TROUGH ALONG 27W. BY TUESDAY MORNING...ALL OF THE GLOBAL MODELS
SHOW GRACE BEING ABSORBED BY A FRONT ASSOCIATED WITH A DEEPENING
EXTRATROPICAL CYCLONE TO THE NORTHWEST OF THE BRITISH ISLES.
 
IT IS WORTH NOTING THAT OTHER ATLANTIC TROPICAL STORMS HAVE FORMED
FARTHER NORTH THAN GRACE DID. IN 2008 TROPICAL STORM LAURA WAS
FIRST CLASSIFIED AS A TROPICAL STORM AT 40.6N....SLIGHTLY FARTHER
NORTH THAN THE LATITUDE OF 40.2N WHERE GRACE WAS FIRST CLASSIFIED
AS A TROPICAL STORM AT 0000 UTC TODAY.  ALSO...IT IS LIKELY THAT
POST-STORM ANALYSIS WILL SHOW GRACE BECOMING A TROPICAL STORM
EARLIER...AND FARTHER SOUTH...THAN INDICATED OPERATIONALLY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 47.7N  14.8W    50 KT
 12HR VT     06/0600Z 50.6N  12.0W    50 KT
 24HR VT     06/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 060241
TCDAT4
TROPICAL STORM GRACE DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092009
1100 PM AST MON OCT 05 2009

GRACE HAS MERGED WITH A FRONTAL BOUNDARY OVER THE FAR NORTHEASTERN
ATLANTIC WITHIN THE PAST HOUR OR SO AND THIS WILL BE THE LAST
ADVISORY ON THIS SYSTEM.  

AN EARLIER QUIKSCAT PASS AT 2026 UTC...PRIOR TO INTERACTION WITH THE
FRONT...SHOWED A FEW 40-45 KT WIND VECTORS TO THE SOUTHEAST OF THE
CENTER.  THE REMNANTS OF GRACE WILL LIKELY PRODUCE A DECREASING AREA
OF GALE FORCE WINDS AS THEY MOVE NORTHEASTWARD ALONG THE FRONTAL
BOUNDARY DURING THE NEXT SEVERAL HOURS.  THE PREVIOUSLY ESTIMATED
MINIMUM PRESSURE MAY HAVE BEEN A FEW MILLIBARS TOO HIGH...AS A
RECENT SHIP OBSERVATION NEAR THE CENTER REPORTED 986.6 MB.  
 
ADDITIONAL INFORMATION ON THE REMNANTS OF GRACE CAN BE FOUND IN HIGH
SEAS FORECASTS ISSUED BY THE UNITED KINGDOM METEOROLOGICAL OFFICE
UNDER WMO HEADER WONT54 EGRR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0300Z 49.7N  13.4W   45 KT
 12HR VT     06/1200Z...ABSORBED BY FRONT
 
$$
FORECASTER BROWN
 

