Tropical Storm GILMA

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TROPICAL STORM GILMA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072012
200 PM PDT WED AUG 08 2012

GILMA HAS BEEN ON THE VERGE OF BECOMING A HURRICANE THROUGHOUT THE
DAY...SHOWING MIXED SIGNALS ABOUT ITS INTENSITY.  SATELLITE
INTENSITY ESTIMATES HAVE BEEN 65 KT FROM TAFB AND 55 KT FROM SAB. 
AMSU INTENSITY ESTIMATES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN
AND CIRA AT COLORADO STATE UNIVERSITY HAVE BEEN 57-63 KT. 
ALSO...EARLIER MICROWAVE DATA SHOWED AT BEST A PARTIAL EYEWALL
UNDER THE CENTRAL DENSE OVERCAST...WHILE LATER VISIBLE IMAGES HAVE
HINTED AT EYE FORMATION.  GIVEN THE AMBIGUITIES...THE INITIAL
INTENSITY WILL REMAIN AT 60 KT...JUST BELOW HURRICANE STRENGTH. 
WHILE THE OUTFLOW REMAINS GOOD IN THE SOUTHWESTERN SEMICIRCLE...A
BAND OF CIRRUS CLOUDS APPROACHING THE STORM FROM THE NORTHEAST
SUGGESTS SOME LIGHT VERTICAL WIND SHEAR IS OCCURRING.
 
THE INITIAL MOTION IS NOW 285/9 KT.  THE CYCLONE IS BEING STEERED
BY A MID- TO UPPER-LEVEL RIDGE EXTENDING WESTWARD OVER THE
NORTHEASTERN PACIFIC FROM THE SOUTHWESTERN UNITED STATES.  THIS
SHOULD KEEP GILMA ON A WEST-NORTHWESTWARD TRACK AT A DECREASING
FORWARD SPEED DURING THE NEXT 24 HR OR SO.  AFTER THAT...THE GLOBAL
MODELS CONTINUE TO SHOW A LARGE AREA OF BROAD LOW- TO MID-LEVEL
CYCLONIC FLOW...POSSIBLY INCLUDING THE REMNANTS OF ATLANTIC
HURRICANE ERNESTO...FORMING TO THE EAST OF GILMA.  THE LATEST
DYNAMICAL MODEL RUNS SHOW THIS FEATURE HAVING LESS OF AN IMPACT ON
GILMA THAN PREVIOUSLY FORECAST...AND AS A RESULT THE GUIDANCE
ENVELOPE HAS SHIFTED WESTWARD AFTER 48 HR.  THE NEW FORECAST TRACK
IS NUDGED A LITTLE TO THE WEST OF THE PREVIOUS FORECAST AND IS IN
BEST OVERALL AGREEMENT WITH THE GFS MODEL.
 
GILMA IS NOW OVER SEA SURFACE TEMPERATURES OF NEAR 27C...AND
THE FORECAST TRACK TAKES THE CYCLONE OVER PROGRESSIVELY COOLER
WATERS.  A LITTLE STRENGTHENING IS POSSIBLE TONIGHT...AND THE
INTENSITY FORECAST STILL CALLS FOR GILMA TO BECOME A HURRICANE. 
STEADY WEAKENING SHOULD OCCUR AFTER 24 HR...WITH THE CYCLONE
FORECAST TO WEAKEN TO A DEPRESSION BY 96 HR AND TO DEGENERATE TO A
REMNANT LOW BY 120 HR.  THE NEW INTENSITY FORECAST IS SIMILAR TO...
BUT A LITTLE ABOVE...THE SHIPS AND LGEM MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 16.1N 117.8W   60 KT  70 MPH
 12H  09/0600Z 16.5N 118.8W   65 KT  75 MPH
 24H  09/1800Z 17.2N 119.9W   65 KT  75 MPH
 36H  10/0600Z 17.8N 120.8W   60 KT  70 MPH
 48H  10/1800Z 18.4N 121.4W   50 KT  60 MPH
 72H  11/1800Z 19.5N 122.0W   40 KT  45 MPH
 96H  12/1800Z 20.0N 122.5W   30 KT  35 MPH
120H  13/1800Z 20.5N 123.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BEVEN
 
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