000
WTNT41 KNHC 291438
TCDAT1
 
TROPICAL STORM KIRK DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112012
1100 AM AST WED AUG 29 2012
 
WHILE KIRK HAS A DISTINCT MID-LEVEL CENTER ON THE SOUTHWEST SIDE OF
THE RELATIVELY DISORGANIZED CONVECTIVE CANOPY...THE LOW-LEVEL
CIRCULATION APPEARS TO BE DISPLACED A LITTLE TO THE WEST DUE TO
ABOUT 15 KT OF WESTERLY SHEAR OVER THE CYCLONE. THE INITIAL
INTENSITY IS HELD AT 40 KT BASED ON A BLEND OF DVORAK FINAL-T
NUMBERS FROM SAB AND TAFB. IN THE SHORT TERM THE COMBINATION OF DRY
AIR AROUND THE CYCLONE AND SHEAR OF 10 TO 15 KT SUGGESTS THAT ANY
INTENSIFICATION WILL BE GRADUAL FOR THE NEXT DAY OR SO. THE NEW NHC
FORECAST HAS BEEN NUDGED SLIGHTLY DOWNWARD THROUGH 36 HOURS BUT IS
STILL ABOVE MOST OF THE GUIDANCE THROUGH THAT TIME. AFTER THAT TIME 
AS KIRK RECURVES AND THE SHEAR DECREASES...STRENGTHENING TO
HURRICANE INTENSITY IS FORECAST BY 72 HOURS IN AGREEMENT WITH THE
INTENSITY CONSENSUS. KIRK IS EXPECTED TO BECOME EXTRATROPICAL BY
THE END OF THE PERIOD WITH SLOW WEAKENING UNDERWAY BY THAT TIME. 

MICROWAVE IMAGERY SUGGESTS THAT THE CENTER WAS LOCATED WEST OF
PREVIOUS ESTIMATES OVERNIGHT...AND THE INITIAL MOTION ESTIMATE IS A
RATHER UNCERTAIN 290/10. KIRK WILL TURN NORTHWESTWARD IN THE NEXT
36 HOURS INTO A BREAK IN THE SUBTROPICAL RIDGE...AND THEN TURN
NORTHWARD AND NORTHEASTWARD AS THE CYCLONE RECURVES INTO THE
MID-LATITUDE WESTERLIES LATE IN THE PERIOD. WHILE THE MODEL
GUIDANCE IS IN AGREEMENT ON THIS OVERALL SCENARIO...THERE REMAIN
SOME SIGNIFICANT DETAIL DIFFERENCES IN THE MOTION IN THE SHORT
TERM. THE ECMWF MODEL KEEPS KIRK WEAKER AND SHOWS MORE GRADUAL
RECURVATURE...WHILE THE GFS...GEFS ENSEMBLE MEAN...AND THE REGIONAL
HURRICANE MODELS SHOW A SHARPER RECURVATURE. THE NEW NHC TRACK IS
FASTER THROUGH 36 HOURS AND A LITTLE TO THE LEFT OF THE PREVIOUS
FORECAST THROUGH THE PERIOD...LARGELY DUE TO THE INITIAL POSITION
AND MOTION. THE NHC TRACK IS CLOSE TO THE LATEST TVCA CONSENSUS
THROUGH 48 HOURS AND A LITTLE TO THE LEFT AFTERWARD...CLOSE TO A
BLEND OF THE GFS AND ECMWF AT DAYS 3 THROUGH 5. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 24.7N  46.9W   40 KT  45 MPH
 12H  30/0000Z 25.3N  48.4W   45 KT  50 MPH
 24H  30/1200Z 26.2N  50.2W   45 KT  50 MPH
 36H  31/0000Z 27.8N  51.7W   50 KT  60 MPH
 48H  31/1200Z 29.8N  52.2W   55 KT  65 MPH
 72H  01/1200Z 34.5N  50.5W   65 KT  75 MPH
 96H  02/1200Z 40.5N  44.0W   65 KT  75 MPH
120H  03/1200Z 48.5N  32.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN