000
AXPZ20 KNHC 270902
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC SUN SEP 27 2015

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0830 UTC.               

...SPECIAL FEATURES...

TROPICAL STORM MARTY CENTERED NEAR 14.3N 103.1W AT 27/0900 UTC 
OR 243 NM SW OF ACAPULCO MEXICO MOVING N AT 5 KT. ESTIMATED 
MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND 
SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED STRONG CONVECTION 
IS WITHIN 60 NM OF THE CENTER. NUMEROUS MODERATE CONVECTION IS 
ELSEWHERE WITHIN 210 NM IN THE E SEMICIRCLE...300 NM IN THE SW 
QUADRANT AND 150 NM IN THE NW QUADRANT. MARTY IS FORECAST TO 
MOVE TO THE N THROUGH TODAY WITH A TURN TO THE NNE AND NE WITH A 
DECREASE IN FORWARD SPEED TONIGHT THROUGH MON NIGHT. MARTY IS 
FORECAST TO APPROACH BUT REMAIN OFFSHORE OF SOUTHWESTERN MEXICO. 
THE FORECAST NOW INCREASES THE STRENGTH OF MARTY TO A HURRICANE 
BY 24 HOURS...THEN WEAKENING BACK TO A TROPICAL STORM BY 48 
HOURS. EVEN IF MARTY DOES STAY OFFSHORE...DEEP TROPICAL MOISTURE 
WILL SPREAD NORTHWARD ACROSS SOUTHWESTERN MEXICO INCREASING THE 
LIKELIHOOD FOR LOCALIZED FLASH FLOODING AND MUDSLIDES. IN 
ADDITION...LARGE SWELLS WILL PROPAGATE TOWARD SHORE RESULTING IN 
DANGEROUS SURF AND AN INCREASED THREAT OF RIP CURRENTS. SEE 
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS.  
    
...TROPICAL WAVES... 
 
TROPICAL WAVE EXITING THE DISCUSSION WATERS FROM 10N TO 15N 
ALONG 139W MOVING W AT 5-10 KT. ONLY ISOLATED CONVECTION IS 
OCCURRING NEAR THE WAVE AXIS. THIS WAVE WILL MOVE COMPLETELY W 
OF 140W LATER THIS MORNING.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE MONSOON TROUGH AXIS EXTENDS FROM 11N108W TO LOW PRES     
NEAR 09N120W TO 12N134W TO 10N139W. NO ITCZ AXIS IS PRESENT. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN   
240 NM SE OF THE AXIS BETWEEN 108W AND 120W. ALSO...SCATTERED 
MODERATE CONVECTION IS FROM 04N TO 08N BETWEEN 86W AND 90W  
WHERE A FAINT PORTION OF THE MONSOON TROUGH MAY BE FORMING.

...DISCUSSION...

A 1008 MB LOW IS EMBEDDED WITHIN THE MONSOON TROUGH NEAR 
09N120W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM IN THE W 
QUADRANT OF THE LOW. SURFACE WINDS NEAR THE LOW ARE RUNNING 5-10 
KT WITH LITTLE CHANGE ANTICIPATED THROUGH THE NEXT 48 HOURS AS 
THE LOW MEANDERS OR DRIFTS TO THE NE-E. 

BROAD SURFACE RIDGING IS ACROSS THE WATERS N OF 20N...EXCEPT IN 
THE NW CORNER WHERE A WEAK COLD FRONT EXTENDS FROM A 1013 MB 
GALE CENTER NEAR 33N135W TO THE SW TO 26N140W AND BEYOND. ONLY 
MODERATE TO FRESH WINDS ARE W OF THE FRONT S OF 30N HOWEVER 
ASSOCIATED SEAS OF 8-9 FT WILL PROPAGATE INTO THE CORNER BY THIS 
EVENING. THE FRONT WILL MANAGE TO DRIFT E-SE WHILE THE LOW 
GRADUALLY WEAKENS.

CROSS-EQUATORIAL SOUTHERLY SWELL COMBINED WITH MODERATE TO  
FRESH WINDS S OF THE MONSOON TROUGH BETWEEN 87W AND 123W IS 
RESULTING IN SEAS OF 8-9 FT ACROSS THE S CENTRAL WATERS. THESE 
CONDITIONS WILL PERSIST THROUGH THE NEXT 24-48 HOURS ACROSS THE 
SAME GENERAL AREA.
 
GULF OF TEHUANTEPEC...THE LOCAL PRES GRADIENT COMBINED WITH 
NOCTURNAL DRAINAGE FLOW IS JUST ENOUGH TO RESULT IN A PULSE AND 
SURGE OF FRESH TO STRONG NORTHERLY WINDS IN THE IMMEDIATE GULF 
WITH RESULTANT SEAS TO 8 FT. THESE CONDITIONS WILL IMPROVE 
SHORTLY AFTER SUNRISE.
     
$$
LEWITSKY