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WTPA44 PHFO 050857
TCDCP4
TROPICAL STORM GUILLERMO DISCUSSION NUMBER 26
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092015
1100 PM HST TUE AUG 04 2015
WE ONCE AGAIN HAVE THE LUXURY OF REAL-TIME IN SITU OBSERVATIONS OF
GUILLERMO...PROVIDED BY US AIR FORCE HURRICANE HUNTERS. THE LATEST
AIRCRAFT DATA...AS WELL AS SATELLITE OBSERVATIONS...INDICATE THAT
GUILLERMO IS BEGINNING TO WEAKEN...WITH MAXIMUM SUSTAINED SURFACE
WINDS ESTIMATED TO BE 55 KT BASED ON SFMR AND FLIGHT LEVEL WINDS.
WHILE WATER TEMPERATURES ALONG THE FORECAST TRACK ARE SUFFICIENTLY
WARM TO SUPPORT A STRONG HURRICANE...PERSISTENT STRONG VERTICAL
SHEAR WILL PRECLUDE THAT FROM OCCURRING. THE CYCLONE HAS MOVED NORTH
OF A RIDGE AXIS ALOFT...AND IS NOW ENCOUNTERING STRONG WESTERLY
WINDS ALOFT...ASSOCIATED WITH THE SUBTROPICAL JET. THE INITIAL
MOTION VECTOR IS ESTIMATED TO BE 295/07 KT...WITH THE RECENT SLOWING
AND WESTWARD TURN LIKELY RELATED TO THE SYSTEM BECOMING INCREASINGLY
DECOUPLED IN THE PRESENCE OF THE STRONG SHEAR...ANALYZED AS BEING AS
HIGH AS 35 KT. WITH EVEN GREATER SHEAR VALUES ALONG THE FORECAST
TRACK...A STEADY WEAKENING TREND IS ANTICIPATED UNTIL DISSIPATION
OCCURS BY DAY 5. SHIPS GUIDANCE DISSIPATES THE SYSTEM WITHIN 72
HOURS...AND THE LATEST ECMWF GUIDANCE OFFERED A DRAMATIC CHANGE FROM
PREVIOUS RUNS...WITH GUILLERMO NOW DEPICTED AS WEAKENING TO AN OPEN
WAVE WITHIN 48 HOURS. THE LATEST INTENSITY FORECAST IS SIMILAR TO
THE PREVIOUS...BUT HAS ACCELERATED THE WEAKENING TREND...AND CLOSELY
FOLLOWS THE IVCN.
AS FAR AS THE TRACK FORECAST...THE MUCH WEAKER SYSTEM ASSUMES A
NEARLY DUE WEST TRACK IN THE LATEST ECMWF GUIDANCE...STEERED BY THE
LOW LEVEL TRADE WIND FLOW...AND THUS THE TVCN AND GFEX CONSENSUS
GUIDANCE HAS SHIFTED SOUTHWARD AGAIN...CONTINUING A TREND THAT BEGAN
ABOUT 12 HOURS AGO. THE UPDATED TRACK FORECAST PARALLELS THE
PREVIOUS...BUT HAS BEEN SHIFTED SLIGHTLY SOUTHWARD...AND CLOSELY
MIRRORS THE GFEX. ALTHOUGH THE PROBABILITY OF SUSTAINED TROPICAL
STORM FORCE WINDS IN THE WATCH AREA HAVE DIMINISHED SLIGHTLY WITH
THIS ADVISORY...NO CHANGES WILL BE MADE TO THE WATCH AT THIS TIME.
12 FOOT SEA RADII WERE EXPANDED IN MOST QUADRANTS DUE TO
OBSERVATIONS FROM NOAA BUOY 51004...WHICH INDICATED THAT CURRENT
WAVE WATCH GUIDANCE WAS UNDERDONE IN THE SOUTHWEST QUADRANT.
FORECAST POSITIONS AND MAX WINDS
INIT 05/0900Z 20.6N 150.3W 55 KT 65 MPH
12H 05/1800Z 21.0N 151.7W 50 KT 60 MPH
24H 06/0600Z 21.9N 153.7W 45 KT 50 MPH
36H 06/1800Z 22.5N 155.6W 40 KT 45 MPH
48H 07/0600Z 23.0N 158.0W 35 KT 40 MPH
72H 08/0600Z 24.0N 162.0W 30 KT 35 MPH
96H 09/0600Z 26.0N 167.0W 25 KT 30 MPH...POST-TROPICAL
120H 10/0600Z...DISSIPATED
$$
FORECASTER BIRCHARD
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