000
AXPZ20 KNHC 252152
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.               

...SPECIAL FEATURE...

A 1007 MB LOW PRESSURE IS EMBEDDED IN THE MONSOON TROUGH NEAR  
11N100W AND IS MOVING NW...OR 295 DEG...AT 9 KT. CURRENTLY 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 
210 NM OVER THE SE SEMICIRCLE OF CENTER. SCATTEROMETER WINDS 
DETECT S-SW 20-25 KT LOW LEVEL WINDS WITHIN 300 NM OVER THE SE 
SEMICIRCLE OF CENTER. CONDITIONS ARE FAVORABLE FOR TROPICAL 
CYCLONE FORMATION WITH THE LOW FORECAST NEAR 12.5N102.5W ON SAT 
AND NEAR 14N102.5W ON SUN.    
    
...TROPICAL LOW AND TROPICAL WAVES... 

A 1007MB SURFACE LOW IS EMBEDDED IN THE MONSOON TROUGH AT   
13N91.5W AND IS DRIFTING NW. CURRENTLY SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS NOTED WITHIN 150 NM OVER THE E 
SEMICIRCLE OF CENTER. A RECENT SCATTEROMETER PASS DETECTED E TO 
SE 20-25 KT SURFACE WINDS WITHIN 150 NM OVER THE E SEMICIRCLE OF 
CENTER. EXPECT THE GRADIENT TO WEAKEN AS THE LOW MOVES TO NEAR 
13N93.5W ON SAT.
 
A TROPICAL WAVE IS ANALYZED FROM 05-18N BETWEEN 104-107W...AND 
HAS BEEN MOVING W AT 10 KT. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED WITHIN 150 NM E AND WITHIN 120 NM W OF THE  
WAVE AXIS.

A TROPICAL WAVE WAS ANALYZED FROM 03N TO 17N ALONG 135W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED S OF 10N 
WITHIN 240 NM OF THE WAVE AXIS.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE TROPICAL LOW PRESSURE CENTERS PREVIOUSLY MENTIONED HAVE  
PULLED THE MONSOON TROUGH AXIS NORTHWARD. THE AXIS IS CURRENTLY 
ANALYZED FROM THE PACIFIC COAST OF NICARAGUA AT 12.5N88W THROUGH 
THE EMBEDDED LOW PRESSURE AT 13N91.5W...THEN TURNS SW THROUGH 
THE SECOND EMBEDDED LOW PRESSURE AT 11N100W...THEN TURNS W ALONG 
10N TO 09N124W WHERE SCATTEROMETER WINDS INDICATE A TRANSITION 
TO AN ITCZ AXIS...WHICH CONTINUES W TO 10N133W...THEN TURNS SW 
TO BEYOND 06N140W. EXCEPT AS PREVIOUSLY DESCRIBED IN ASSOCIATION 
WITH TROPICAL LOWS AND TROPICAL WAVES...SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS NOTED WITHIN 90 NM OF 06N79W AND 
WITHIN 150 NM EITHER SIDE OF A LINE FROM 06N110W TO 09N130W. 

...DISCUSSION...

A SURFACE RIDGE EXTENDS SE FROM A SURFACE HIGH AT 32N131W TO  
13N107W. A PRE-FRONTAL TROUGH HAS MOVED INTO THE NW PORTION FROM 
32N132W TO 26N140W. AN INITIAL COLD FRONT ANALYZED FROM 32N136W 
TO BEYOND 29N140W WILL CONTINUE SE REACHING A POSITION FROM 
32N135W TO 26N136W LATE SAT NIGHT. STRENGTHENING HIGH PRESSURE 
NW OF THE FRONT WILL INCREASE THE POST-FRONTAL NW FLOW TO 20-25 
KT WITH COMBINED SEAS BUILDING TO 12 FT NEAR 32N140W ON SUN. 
EXPECT THE FRONT TO STALL FROM NEAR 32N132W TO 23N136W ON MON. 
NORTHERLY WINDS W OF THE FRONT WILL DIMINISH TO 15 KT S OF 
32N...BUT COMBINED SEAS OF 8-11 FT ARE EXPECTED W OF A LINE FROM 
32N136W TO 27N140W ON MON.
  
GAP WINDS...PULSES OF STRONG N-NE WINDS ARE EXPECTED ACROSS AND  
DOWNSTREAM OF THE GULF OF TEHUANTEPEC THROUGH LATE SAT THEN THE 
GRADIENT WILL RELAX SUPPORTING ONLY 15-20 KT DRAINAGE FLOW LATE 
SUN NIGHT INTO MON.  
    
$$
NELSON