000
AXPZ20 KNHC 200315
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
0405 UTC SUN SEP 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0130 UTC.               

...SPECIAL FEATURES...

A PAIR OF LOW PRESSURE CENTERS ARE EMBEDDED WITHIN THE MONSOON 
TROUGH...THE MAIN LOW NEAR 21.5N112W AND THE OTHER NEAR 
14.5N118W. SCATTERED MODERATE TO STRONG CONVECTION CONTINUES 
WITHIN 150 NM ACROSS THE W SEMICIRCLE...WHILE SCATTERED MODERATE 
TO STRONG CONVECTION HAS INCREASED FROM 23N TO 26.5N BETWEEN 
108W AND 113W...INCLUDING THE GULF OF CALIFORNIA AND BAJA 
CALIFORNIA SUR. THERE REMAINS THE POTENTIAL FOR THIS LOW TO 
DEVELOP INTO A TROPICAL CYCLONE DURING THE NEXT 24 HOURS OR SO 
AS IT MOVES IN A N-NW DIRECTION...THEN WILL MOVE ACROSS PORTIONS 
OF BAJA CALIFORNIA AND BEGIN TO ENCOUNTER A LESS FAVORABLE 
ENVIRONMENT. 

THE MONSOONAL FLOW WILL CONTINUE TO ADVECT ABUNDANT TROPICAL 
MOISTURE ACROSS SOUTHERN BAJA CALIFORNIA AND INTO CENTRAL 
PORTIONS AS WELL AS THE ADJACENT GULF AND MEXICAN STATES TO THE 
E THROUGH SUNDAY. THIS TROPICAL MOISTURE SHOULD THEN SPREAD 
FARTHER NW-N ACROSS NORTHERN BAJA CALIFORNIA...AND MAY REACH FAR 
SOUTHERN CALIFORNIA MON INTO TUE. INCREASING RAIN CHANCES SHOULD 
BE EXPECTED ACROSS THESE AREAS...EXTENDING INLAND ACROSS 
MAINLAND MEXICO TO THE W SLOPES OF THE SIERRA MADRES 
OCCIDENTALES...WITH THE POTENTIAL FOR HEAVY RAINS...FLASH 
FLOODING AND LANDSLIDES THROUGH THE WEEKEND. 

...TROPICAL WAVES... 

A TROPICAL WAVE IS INVOF 90W-91W...EXTENDING FROM INTERIOR OF 
YUCATAN PENINSULA S TO 91W. SCATTERED MODERATE TO STRONG 
CONVECTION ASSOCIATED WITH THIS WAVE CONTINUES ACROSS THE 
YUCATAN PENINSULA ALONG AND AHEAD OF THIS WAVE...AS WELL AS 
CENTRAL AMERICA ON BOTH SIDES OF THE WAVE AXIS...WHILE A FEW  
ISOLATED MODERATE CONVECTIVE CELLS ARE NOTED ALONG ABOUT 09N 
JUST AHEAD OF THE WAVE.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 10N74W TO 08N80W 
TO 11N96W TO 09N110W...WHERE IT REMAINS FRACTURED...THEN RESUMES 
FROM COMPLEX LOW PRES NEAR 21.5N112W TO LOW PRES NEAR 14.5N118W 
TO BEYOND 11N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
NOTED WITHIN 60 NM N AND 330 NM S OF TROUGH BETWEEN 98W AND 
110W. SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 120 
NM NW AND 150 NM SE OF TROUGH BETWEEN 112W AND 123W. ISOLATED TO 
SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 90 NM 
N AND 240 NM S OF TROUGH BETWEEN 123W AND 140W. 
 
...DISCUSSION...

A 1024 MB HIGH IS CENTERED NW OF THE AREA NEAR 37N145W AND 
EXTENDS A RIDGE SE TO NEAR 26N114W. THE PRES GRADIENT BETWEEN 
THE RIDGE AND MONSOON TROUGH IS PRODUCING MODERATE TO FRESH NE 
TRADE WINDS OVER MOST OF THE WESTERN WATERS. THIS IS PRODUCING 
SEAS TO 8 FT FROM FROM 17N TO 23N W OF 133W. THE HIGH PRESSURE 
CENTER WILL SHIFT FURTHER FROM THE AREA OVER THE NEXT 24 HOURS 
WHICH WILL LOOSEN THE PRESSURE GRADIENT AND DIMINISH TRADE WINDS 
MODESTLY OVER THIS AREA AND ASSOCIATED SEAS WILL SUBSIDE BELOW 8 
FT.
 
GAP WINDS... N WINDS OF 20-25 KT ARE EXPECTED TO BEGIN ACROSS 
THE GULF OF TEHUANTEPEC EARLY ON MON AND PULSE EACH NIGHT TO 25 
KT...POSSIBLY 30 KT...THROUGH TUESDAY NIGHT. 
 
$$
STRIPLING