000
AXPZ20 KNHC 020252
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
0405 UTC FRI AUG 02 2013

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURES... 
HURRICANE GIL AT 14.3N 125.1W AT 01/2100 UTC MOVING W OR 270 DEG
AT 10 KT.  MAXIMUM SUSTAINED WIND 75 GUSTS TO 90 KT AND MINIMUM
CENTRAL PRES 985 MB.  CURRENTLY...NUMEROUS STRONG CONVECTION IS
WITHIN 90 NM NW AND WITHIN 30 NM SE SEMICIRCLES OF CENTER. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IN BANDS ELSEWHERE
WITHIN 150 NM OF CENTER. GIL STILL REMAINS UNDER FAVORABLE UPPER
LEVEL CONDITIONS AS ANTICYCLONE ALOFT ENHANCES HURRICANE OUTFLOW.
NEVERTHELESS GIL WESTWARD TRACK WILL BRING IT CLOSER TO A REGION
OF INCREASING SW SHEAR AND SEA SURFACE TEMPERATURES ARE JUST N
OF GIL. FORECAST MAINTAINS GIL HOLDING ITS OWN FOR ANOTHER 24-36
HOURS BEFORE THE ONSET OF A WEAKENING TREND. SEE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTNT22 KNHC
FOR ADDITIONAL DETAILS.

LOW PRES CENTER AT 13N117W MOVE W AT 8 KT FOLLOWS IN WAKE OF GIL.
WHILE UPPER ENVIRONMENT IS SIMILAR TO THE ONE OVER GIL DUE TO 
THEIR PROXIMITY...OUTFLOW FROM GIL SEEM TO BE DISRUPTIVE AND
DOES NOT ALLOW ANY SIGNIFICANT INTENSIFICATION OF LOW PRES
CENTER. IT BARELY HOLDS ITS STRENGTH STEADY...NOT QUITE READY TO
BE DISCARDED ALTHOUGH PROBABILITY OF IT BECOMING A TROPICAL
CYCLONE WITHIN THE NEXT 48 HOURS HAS BEEN LOWERED TO 30 PERCENT.
CURRENTLY SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN
150 NM OVER SW SEMICIRCLE. 
 
SECOND LOW PRES CENTER FORMED EARLY TONIGHT NEAR 12N136W 1009 MB.
NUMEROUS MODERATE AND SCATTERED STRONG CONVECTION NOTED WITHIN
90 NM IN ITS E QUADRANT AND SCATTERED MODERATE CONVECTION WITHIN
60 NM ELSEWHERE.  WHILE NOT ENTIRELY IN A FAVORABLE UPPER LEVEL 
ENVIRONMENT...SYSTEM HAS ABUNDANT TROPICAL MOISTURE AVAILABLE 
AND WARM SEA SURFACE TEMPERATURES TO ENHANCE ITS DEVELOPMENT.   

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 102N104W TO 1009 MB
LOW PRES AT 13N117W. ITCZ AXIS STRETCHES FROM 14N129W TO LOW 
PRES 1009 MB AT 12N136W TO BEYOND 10N140W.  MODERATE TO STRONG
CONVECTION WITHIN 150 NM S OF AXIS E OF 84W AND WITHIN 120 NM N
OF AXIS W OF 133W.

...DISCUSSION...                                              
BOTH THE UPPER LEVEL CYCLONE AT 28N145W AND ITS ATTENDANT TROUGH
EXTENDING TO 14N150W HAVE RETREATED W BUT STILL BRINGING DRY AIR
MASS INTO E PAC N OF 18N W OF 119W...ALTHOUGH DIMINISHING IN
STRENGTH. THIS BRINGS AN INTERESTING CONTRAST WITH PREVIOUSLY
EXPECTED STRONG SOUTHWESTERLIES TO SHEAR AND DECOUPLE HURRICANE
GIL APART. RESULT MAY ALLOW FOR A LONGER PERIOD OF INTENSIFY AND
/OR A SLOWER DECAY OF GIL. LARGE UPPER LEVEL E-W QUASI-
STATIONARY RIDGE ACROSS CENTRAL E PAC HAS BEEN HOLDING HURRICANE
GIL AND LOW PRES NEAR 13N116W ALIVE BY PROVIDING GOOD OUTFLOW
ENVIRONMENT.  

...AT THE LOWER LEVELS...
BROAD SURFACE RIDGE 1028 MB AT 33N146W MAINTAINS STEADY FLOW OF 
FRESH NE TRADES...BUT NOW DIMINISHING AS RIDGE WEAKENS AND 
RETREATS W.  CURRENT SEAS TO 8 FT N OF 18N W OF 120W EXPECTED TO SUBSIDE.

$$ 
WALLY BARNES