000
WTPZ45 KNHC 140832
TCDEP5
HURRICANE GUILLERMO DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102009
200 AM PDT FRI AUG 14 2009
 
GUILLERMO IS UPGRADED TO A 65-KT HURRICANE BASED ON THE APPEARANCE
OF AN EYE IN MICROWAVE IMAGERY FROM A 0151 UTC SSMIS PASS AND A
0218 UTC AMSU PASS...ALONG WITH CONSENSUS DVORAK T-NUMBERS OF 4.0
FROM TAFB AND SAB AT 0600 UTC. ALTHOUGH THE EYE IS NOT APPARENT IN
GEOSTATIONARY INFRARED IMAGERY...THE CENTER APPEARS TO BE LOCATED
ON THE NORTHERN SIDE OF THE CDO BETWEEN TWO CURVED BANDS OF COLD
CLOUD TOPS THAT HAVE DEVELOPED OVER THE PAST COUPLE OF HOURS.
 
VERTICAL SHEAR IS FORECAST TO REMAIN LOW AND THE SYSTEM WILL REMAIN
OVER SSTS ABOVE 26C FOR THE NEXT 12 TO 24 HOURS...SO SOME SLIGHT
STRENGTHENING IS FORECAST IN THE SHORT TERM. AFTER 24 HOURS...THE
INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...SHOWING A
GRADUAL SPIN DOWN AS THE CYCLONE ENTERS PROGRESSIVELY COOLER WATERS
AND VERTICAL SHEAR INCREASES. THE FORECAST IS CLOSE TO THE
INTENSITY CONSENSUS ICON THROUGH 72 HOURS...BUT IS BELOW ICON AT
DAYS 4 AND 5...AS THE HWRF AND ESPECIALLY THE GFDL SEEM TOO SLOW TO
WEAKEN GUILLERMO GIVEN THE HOSTILE ENVIRONMENT EXPECTED AT THAT
TIME.
 
MICROWAVE IMAGERY AND AN AMBIGUITY ANALYSIS FROM A 0259 UTC QUIKSCAT
PASS SHOW THAT GUILLERMO IS LOCATED SLIGHTLY TO THE NORTH OF THE
PREVIOUS FORECAST TRACK...WITH AN INITIAL MOTION ESTIMATE OF
280/13. THE TRACK FORECAST REASONING REMAINS UNCHANGED. GUILLERMO
IS MOVING AROUND THE SOUTHWESTERN PERIPHERY OF THE MID-LEVEL
SUBTROPICAL RIDGE AND WILL FEEL THE INFLUENCE OF A WEAKNESS IN THE
RIDGE THAT DEVELOPS EAST-NORTHEAST OF THE HAWAIIAN ISLANDS BY DAYS
4 AND 5. THEREFORE...A WEST TO WEST-NORTHWEST MOTION IS EXPECTED
THROUGH THE PERIOD...EVEN AFTER THE CYCLONE BECOMES A SHALLOWER
SYSTEM. THE TRACK FORECAST HAS BEEN ADJUSTED A LITTLE TO THE NORTH
OF THE PREVIOUS PACKAGE TO ACCOUNT FOR THE INITIAL MOTION AND A
NORTHWARD SHIFT IN THE TVCN TRACK MODEL CONSENSUS.
 
THE INITIAL 34-KT WIND RADII WERE ADJUSTED BASED ON DATA FROM THE
THE AFOREMENTIONED QUIKSCAT PASS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 17.6N 125.9W    65 KT
 12HR VT     14/1800Z 17.9N 127.9W    70 KT
 24HR VT     15/0600Z 18.4N 130.5W    70 KT
 36HR VT     15/1800Z 19.0N 133.1W    60 KT
 48HR VT     16/0600Z 19.6N 135.7W    55 KT
 72HR VT     17/0600Z 21.0N 141.0W    45 KT
 96HR VT     18/0600Z 22.0N 146.0W    35 KT
120HR VT     19/0600Z 23.0N 151.0W    30 KT
 
$$
FORECASTER BRENNAN