000
AXPZ20 KNHC 250924
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC FRI SEP 25 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 
0900 UTC.               

...TROPICAL WAVES...

TROPICAL WAVE ALONG 103W FROM 04N TO 16N MOVING W AT 5-10 KT. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 06N  
TO 12N WITHIN 180 NM W OF THE WAVE AXIS. THE WAVE HAS BEEN 
DIFFICULT TO TRACK HOWEVER THERE IS BROAD 700 MB TROUGHING 
BETWEEN 100W AND 104W ALONG WITH 850 MB VORTICITY MAXIMUM NOTED 
FROM 09N TO 12N NEAR THE WAVE AXIS.

TROPICAL WAVE ALONG 135W FROM 04N TO 19N MOVING W AT 10-15 KT. 
SCATTERED MODERATE CONVECTION IS FROM 15N TO 18N WITHIN 180 NM E 
OF THE WAVE AXIS. 700 MB TROUGHING IS NOTED BETWEEN 135W AND 
138W WHILE RECENT SCATTEROMETER PASSES INDICATED A WIND SHIFT  
AT THE SURFACE.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE MONSOON TROUGH AXIS EXTENDS FROM 11N84W TO LOW PRES      
NEAR 12N92W TO 10N110W TO 11N120W TO 11N133W. NO ITCZ AXIS IS 
PRESENT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION     
IS FROM 07N TO 11N BETWEEN 97W AND 102W. ALSO...SCATTERED 
MODERATE CONVECTION IS N OF 14N BETWEEN 96W TO 100W UNDER AN 
AREA OF UPPER LEVEL DIFFLUENCE.

...DISCUSSION...

A 1006 MB SURFACE LOW IS EMBEDDED IN THE MONSOON TROUGH AT 
12N92W. THE LOW HAD BEEN STATIONARY FOR SEVERAL HOURS BUT HAS 
NOW TAKEN A NNW MOVEMENT AROUND 5 KT. SCATTERED MODERATE AND 
ISOLATED STRONG CONVECTION IS WITHIN 270 NM IN THE NE SEMICIRCLE 
OF THE LOW. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH 
BOTH THE GFS AND ECMWF NOW SHOWING SLOW DEVELOPMENT OF THE LOW 
WITH AT LEAST 20-30 KT WINDS BY 48 HOURS. WILL WAIT FOR MORE RUN 
TO RUN CONSISTENCY BEFORE ENHANCING THIS LOW IN THE FORECAST. IN 
THE MEANTIME...THE PROXIMITY OF THE LOW TO CENTRAL AMERICA WILL 
RESULT IN HEAVY RAINFALL OVER PORTIONS OF EL SALVADOR...SOUTHERN 
GUATEMALA AND SOUTHEASTERN MEXICO THROUGH AT LEAST THE NEXT 48 
HOURS.

A SURFACE RIDGE EXTENDS FROM 1017 MB HIGH PRES WELL N OF THE 
DISCUSSION WATERS NEAR 37N128W THROUGH 28N124W TO 19N110W. 
SCATTEROMETER DATA INDICATES GENTLE TO MODERATE WINDS W OF   
110W WHERE 4-7 FT SEAS ALSO PREVAIL. A COLD FRONT IS JUST NW OF 
THE AREA. THE FRONT WILL SAG SLOWLY TO THE SE INTO SAT BEFORE 
STALLING WITH LOW PRES DEVELOPING ALONG IT JUST N OF THE 
DISCUSSION WATERS.

LOOKING AHEAD...THE LOW WILL DEEPEN THROUGH LATE SAT AND FRESH 
TO GALE FORCE WINDS WILL DEVELOP ON THE NW SIDE OF THE LOW STILL 
N OF THE AREA BY EARLY SUN. THIS WILL SEND FRESH TO STRONG WINDS 
AND BUILDING SEAS OF 8-12 FT INTO THE NW CORNER BY SUN.

GAP WINDS...PULSES OF FRESH TO NEAR GALE FORCE N-NE WINDS ARE 
EXPECTED ACROSS AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC 
THROUGH THE WEEKEND WITH THE STRONGEST WINDS EXPECTED DURING 
MAXIMUM DRAINAGE AROUND SUNRISE EACH MORNING. SEAS WILL BUILD TO 
UP TO 11 FT DOWNSTREAM OF THE GULF. 
    
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LEWITSKY