000
AXPZ20 KNHC 251003
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED NOV 25 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0815 UTC.

...ITCZ...

AXIS ANALYZED FROM 08N78W TO 08N87W TO 05N97W TO 07N110W TO 
06N116W TO 08N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WITHIN 90 NM N OF AXIS AND 170 NM S OF AXIS E OF 
89W.   

...DISCUSSION...

LIMITED ITCZ CONVECTION OVER THE W PORTION OF THE FORECAST AREA 
THE PAST COUPLE OF DAYS RESULTED IN A WEAKENED UPPER LEVEL RIDGE 
ACROSS THE FORECAST AREA. THIS HAS ENABLED AN UPPER LEVEL TROUGH 
TO PROGRESS INTO THE FORECAST AREA...WITH TROUGH AXIS CURRENTLY 
CENTERED NEAR 121W. THE MAIN AFFECT OF THIS FEATURE HAS BEEN TO 
WEAKEN THE SURFACE HIGH PRESSURE N OF THE AREA...AND BRING A 
DECREASE IN THE COVERAGE OF STRONG TRADEWINDS ACROSS THE W PART 
OF THE AREA. 

AT THE SURFACE...AFOREMENTIONED HIGH PRESSURE 1025 MB CENTERED 
NEAR 35N131W HAS WEAKENED SLIGHTLY SINCE LAST NIGHT AND WINDSAT 
AND ASCAT INDICATE A SMALLER AREA OF STRONG TRADES THAN THE PAST 
SEVERAL NIGHTS. THIS HIGH PRESSURE WILL CONTINUE TO WEAKEN AND 
DISSIPATE THU...THEN ANOTHER STRONG HIGH PRESSURE CENTER WILL 
MOVE N OF THE AREA ON FRI. THIS WILL MAINTAIN A SMALL AREA OF 
FRESH TO STRONG TRADES BEFORE INCREASING IN SIZE ON FRI. SEAS UP 
TO 12 FT REMAIN IN THE W PORTION OF THE FORECAST AREA DUE TO 
LINGERING NW SWELLS. ANOTHER SET OF LONG PERIOD NW SWELL HAS 
BEEN GENERATED BEHIND STRONG LOW PRESSURE 973 MB IN THE N 
PACIFIC OCEAN NEAR 51N143W AT 06 UTC. THESE LONG PERIOD SWELLS 
WILL MOVE INTO THE NW PORTION OF THE FORECAST AREA BY THU 
MORNING WITH SEAS TO 16 FT POSSIBLE IN THE FAR NW PORTION. 

...GAP WINDS...

MODERATE TO FRESH TRADEWIND FLOW IN THE SW CARIBBEAN IS HELPING 
FOR NE TO E WINDS OF 20 TO 25 KT IN THE GULF OF PAPAGAYO AND 
SURROUNDING WATERS. THE WINDS ARE ENHANCED DURING THE OVERNIGHT 
AND EARLY MORNING HOURS DUE TO ADDITIONAL CONTRIBUTION FROM 
DRAINAGE FLOW. WITH MODERATE TO FRESH TRADEWIND FLOW CONTINUING 
IN THE SW CARIBBEAN...THESE CONDITIONS ARE EXPECTED TO PERSIST 
THROUGH THE REMAINDER OF THE WEEK.

STRONG HIGH PRESSURE OVER IDAHO COMBINED WITH A LOW PRESSURE 
TROUGH W OF BAJA CALIFORNIA...THE REFLECTION OF THE UPPER LEVEL 
TROUGH...IS MAINTAINING A TIGHT PRESSURE GRADIENT...AND FRESH TO 
STRONG NW TO N WINDS IN THE GULF OF CALIFORNIA. THE PRESSURE 
GRADIENT WILL DECREASE AS THE HIGH PRESSURE STARTS TO WEAKEN AND 
SHIFT SE OVER THE NEXT 24 TO 30 HOURS...WHICH WILL BRING A 
DECREASE IN THE WINDS.

ANOTHER TEHUANTEPEC GALE EVENT IS EXPECTED TO START TONIGHT AS A 
STRONG COLD FRONT HAS PUSHED INTO THE S GULF OF MEXICO. WINDS 
WILL BECOME FRESH TO STRONG THIS MORNING...AND ARE EXPECTED TO 
INCREASE TO GALE FORCE TONIGHT. 

$$

AL