706  
AXPZ20 KNHC 090330  
TWDEP  
 
TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL  
0405 UTC THU NOV 09 2017  
 
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
 
 
A TIGHT PRESSURE GRADIENT HAS SET UP OVER SOUTHEASTERN MEXICO,  
AND IS BRINGING STRONG NORTHERLY WINDS THROUGH THE ISTHMUS OF  
TEHUANTEPEC AND ACROSS THE GULF OF TEHUANTEPEC WHERE SEA SURFACE  
TEMPERATURES ARE QUITE WARM, 29.5 TO 30.5 DEG. CELSIUS. THESE  
CONDITIONS ARE EXPECTED TO CONTINUE INTO THURSDAY MORNING. HIGH  
PRESSURE SURGING SOUTHWARD BEHIND A COLD FRONT MOVING ACROSS THE  
WESTERN GULF OF MEXICO WILL PUSH A COOLER AIR MASS TOWARDS THE  
EASTERN SLOPES OF THE SIERRA ORIENTAL MOUNTAINS ALONG EASTERN  
MEXICO THAT WILL ACT TO FURTHER TIGHTEN THE PRESSURE GRADIENT  
ALREADY IN PLACE ALLOWING FOR THESE WINDS TO INCREASE TO GALE  
FORCE BY EARLY THURSDAY AFTERNOON. A GALE WARNING IS ALREADY IN  
EFFECT FOR THE GULF OF TEHUANTEPEC THROUGH 48 HOURS, AND MOST  
LIKELY WILL HAVE TO EXTEND BEYOND THE 48 HOUR FORECAST PERIOD OF  
THE DISCUSSION. SEAS ARE EXPECTED TO BUILD TO THE RANGE OF ABOUT  
10-15 FT WITH THESE GALE CONDITIONS. MODEL GUIDANCE SUGGESTS  
THAT THIS EVENT WILL LAST THROUGH THE NEXT FEW DAYS, WHILE  
PULSING DOWN TO JUST BELOW GALE FORCE IN THE LATE MORNINGS.  
   
..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH
 
 
THE MONSOON TROUGH AXIS EXTENDS FROM 10N85W TO 10N100W TO  
08N110W TO LOW PRESSURE NEAR 10N122W 1009 MB TO 10N138W WHERE  
SCATTEROMETER WINDS FROM THIS AFTERNOON INDICATE THE ITCZ THEN  
BEGINS AND CONTINUES TO BEYOND 08N140W. SCATTERED MODERATE  
CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 83W-86W,  
WITHIN 120 NM N OF THE AXIS BETWEEN 102W-108W AND ALSO WITHIN  
60 NM N OF THE AXIS BETWEEN 117W-119W.  
   
..DISCUSSION
 
 
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...  
 
A RIDGE WILL DOMINATE THE WATERS W OF BAJA CALIFORNIA THROUGH THE  
REST OF THE WEEK, WHILE A TROUGH WILL MEANDER BETWEEN THE COAST  
OF NW MEXICO AND THE GULF OF CALIFORNIA. MODERATE TO LOCALLY  
FRESH NW TO N FLOW WILL PREVAIL ACROSS THE WATERS W OF BAJA  
CALIFORNIA, INCREASING TO FRESH TO LOCALLY STRONG OFFSHORE OF  
THE NORTHERN WATERS THU NIGHT THROUGH FRI. A COLD FRONT IS  
EXPECTED TO WEAKEN BEFORE REACHING THE AREA ON FRIDAY, BUT THE  
ASSOCIATED LONG-PERIOD NW SWELL INDUCING SEAS IN THE RANGE OF 8-  
10 FT WILL PROPAGATE SOUTHEASTWARD ACROSS THE WATERS N OF 23N  
AND TO THE W OF BAJA CALIFORNIA ON FRIDAY, THEN SPREAD SOUTHWARD  
THROUGH ALL THE WATERS W OF BAJA ON SATURDAY WHILE SUBSIDING  
SLIGHTLY.  
 
A RELATIVELY STRONG JET STREAM BRANCH FROM THE CENTRAL PACIFIC  
WATERS IS ADVECTING ABUNDANT MOISTURE ENE TOWARDS NORTHERN AND  
CENTRAL BAJA CALIFORNIA AND FAR SOUTHERN CALIFORNIA. THIS  
MOISTURE CONSISTS OF MULTILAYER CLOUDS WITH POSSIBLE ISOLATED  
SHOWERS AND THUNDERSTORMS UNDERNEATH THEM.  
 
GULF OF CALIFORNIA: THE PRESSURE GRADIENT WILL TIGHTEN A LITTLE  
RESULTING IN A NARROW SWATH OF FRESH TO LOCALLY STRONG NW WINDS  
FROM 25N TO 28N BY THIS AFTERNOON. THE PRESSURE GRADIENT WILL  
RELAX WITH MODERATE NW FLOW ONLY TO THE S OF 26N BY THURSDAY  
EVENING. MAINLY LIGHT AND VARIABLE WINDS AND SEAS OF 2 FT OR LESS  
WILL THEN PREVAIL FOR THE END OF THE WEEK INTO THE UPCOMING  
WEEKEND.  
 
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND  
WITHIN 750 NM OF ECUADOR...  
 
GULF OF PAPAGAYO: MODERATE NE WINDS WILL PULSE DURING THE  
OVERNIGHT HOURS TONIGHT, WITH SEAS BUILDING TO 5 OR 6 FT  
DOWNSTREAM OF THE GULF NEAR 11N87W.  
 
LIGHT AND VARIABLE WINDS AND 4 TO 6 FT SEAS, ARE EXPECTED  
ELSEWHERE TO THE N OF 09N, WHILE MODERATE TO LOCALLY FRESH  
SOUTHERLY WINDS AND 5 TO 7 FT SEAS, ARE FORECAST S OF 09N  
THROUGH THE REMAINDER OF THE WEEK AND THE UPCOMING WEEKEND.  
 
REMAINDER OF THE AREA...  
 
A 1020 MB HIGH PRESSURE SYSTEM IS ANALYZED NEAR 26N132W AND  
EXTENDS A RIDGE SOUTHEASTWARD TO NEAR 23N119W AND WESTWARD TO  
NEAR 26N139W. THIS HIGH CENTER IS FORECAST TO REMAIN NEARLY  
STATIONARY THROUGH THURSDAY MORNING, THEN TRACK NORTHEASTWARD TO  
NEAR 29N124W BY THURSDAY EVENING. A LOW-LEVEL TROUGH IS  
ROUGHLY ALONG 134W FROM 11N TO 18N. SCATTERED MODERATE  
CONVECTION IS SEEN WITHIN 60 NM E AND WITHIN 180 NM W OF THE  
TROUGH FROM 13N TO 18N AS IT IS BEING ENHANCED BY A NEARLY  
STATIONARY UPPER LEVEL LOW AT 15N139W. A 1009 MB LOW PRESSURE  
SYSTEM REMAINS EMBEDDED WITHIN THE MONSOON TROUGH NEAR 10N122W.  
AN ASCAT PASS FROM 1758Z WEDNESDAY AFTERNOON HIGHLIGHTED WINDS  
OF 20 KT WITHIN 120 NM OF THE LOW IN THE NE QUADRANT, AND WITHIN  
60 NM OF THE LOW IN THE SE QUADRANT. LATEST SATELLITE IMAGERY  
SHOWS THAT THE EARLIER OBSERVED SCATTERED MODERATE ISOLATED  
STRONG CONVECTION THAT WAS WITHIN 60 NM NW AND SE QUADRANTS OF  
THE LOW HAS SIGNIFICANTLY DIMINISHED. ONLY SCATTERED MODERATE  
CONVECTION REMAINS WITHIN 60 NM OF THE LOW IN THE NW QUADRANT.  
THE LOW IS FORECAST TO MOVE GENERALLY WESTWARD TO NEAR 10N127W BY  
EARLY THURSDAY EVENING AND TO NEAR 12N131W BY EARLY FRIDAY  
EVENING.  
 
A COLD FRONT HAS MOVED INTO THE FAR NW CORNER OF THE FORECAST  
AREA. THE MAIN ISSUE WITH THIS FRONT WILL RELATED TO ITS  
IMPACTS ON WAVEHEIGHTS. IT IS FOLLOWED BY A NEW SET OF LONG  
PERIOD NW SWELL. THE FRONT WILL REACH FROM NEAR 32N138W TO  
28N132W, AND AS A WEAKENING STATIONARY FRONT TO 27N140W BY EARLY  
THURSDAY EVENING, THEN QUICKLY BEGIN TO DISSIPATE AS HIGH  
PRESSURE BEHIND IT OVERTAKES IT NEAR A POSITION FROM 32N116W TO  
28N125W AND DISSIPATING STATIONARY FROM THERE TO 26N140W BY  
LATE FRIDAY AFTERNOON INTO FRIDAY EVENING. THE ASSOCIATED LONG  
PERIOD NW SWELL, WITH SEAS OF 8 TO 13 FT SEAS WILL PROPAGATE  
SOUTHEASTWARD THROUGH THE NORTHERN FORECAST WATERS WHILE  
DECAYING. SEAS OF 8 FT OR GREATER WILL COVER THE WATERS N OF 15N  
W OF 115W BY FRIDAY EVENING, THEN BEGIN TO SUBSIDE TO NEAR 8 FT  
THROUGHOUT THE WATERS BY SUNDAY EVENING.  
 
A PRETTY STRONG JET STREAM BRANCH EXTENDS FROM THE DEEP TROPICS  
OF THE CENTRAL PACIFIC NORTHEASTWARD TOWARDS THE NE PORTION OF  
THE AREA. LATEST SATELLITE IMAGERY SHOWS BROKEN TO OVERCAST  
MULTILAYER CLOUDS ALONG AND S OF THE JETSTREAM BRANCH ROUGHLY  
WITHIN 90 NM EITHER SIDE OF A LINE FROM 19N134W TO 25N125W TO  
29N120W, AND WELL NE FROM THERE TOWARDS NORTHERN BAJA CALIFORNIA  
AND SOUTHERN CALIFORNIA AS MENTIONED ABOVE. UPPER DISTURBANCES  
RIDING NORTHEASTWARD ALONG THIS JET STREAM ARE HELPING TO  
ENHANCE THE AFOREMENTIONED CLOUDINESS AS WELL AS TRIGGER OFF  
SMALL POCKETS OF ISOLATED SHOWERS AND THUNDERSTORMS. THIS  
JETSTREAM BRANCH SET UP IS FORECAST TO CHANGE LITTLE OVER THE  
NEXT 24-48 HOURS.  
 

 
AGUIRRE  
 
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