000
AXPZ20 KNHC 262212
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU NOV 26 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
2130 UTC.               

...SPECIAL FEATURES...

AT 2100 UTC...HURRICANE SANDRA WAS CENTERED NEAR 16.8N
110.1W...OR ABOUT 365 NM S OF THE SOUTHERN TIP OF THE BAJA
CALIFORNIA PENINSULA. SANDRA IS MOVING N OR 360 DEGREES AT 10 KT
WITH A GRADUAL SHIFT TOWARDS THE N-NE EXPECTED ON FRIDAY.
ESTIMATED MINIMUM CENTRAL PRESSURE WAS 956 MB.
SOUTHWESTERLYUPPER LEVEL WIND SHEAR HAS BEGUN TO IMPACT
SANDRATHIS AFTERNOON...AND MAXIMUM SUSTAINED WINDS HAS DECREASED
SLIGHTLY TO 105 KT WITH GUSTS 130 KT...A CATEGORY THREE
HURRICANE. NUMEROUS STRONG CONVECTION WAS OCCURRING WITHIN 50
ACROSS THE N AND 75 NM S SEMICIRCLES...WHILE SCATTERED TO
NUMEROUS MODERATE TO STRONG CONVECTION WAS ELSEWHERE WITHIN 270
NM NE SEMICIRCLE...180 NM S AND 120 NM W QUADRANTS. AS
SANDRAMOVES N AND THEN N-NE TONIGHT AND FRIDAY...THE UPPER LEVEL
WIND SHEAR IS EXPECTED TO INCREASE ACROSS THE SYSTEM...AND A
FAIRLY QUICK WEAKENING TREND IS EXPECTED...WITH SANDRA REACHING
TROPICAL STORM STRENGTH ON FRI NIGHT AS IT APPROACHES THE
SOUTHERN TIP OF BAJA CALIFORNIA. INTERESTS IN THE SOUTHERN
PORTIONS OF THE BAJA PENINSULA AS WELL ALONG THE CENTRAL PACIFIC
COAST OF MEXICO SHOULD MONITOR THE PROGRESS OF SANDRA. CLUSTERS
OF STRONG THUNDERSTORMS WILL SOON MOVE ONSHORE THE PACIFIC COAST
OF MAINLAND MEXICO BETWEEN 18-24N RESULTING IN LARGE RAINFALL
ACCUMULATIONS THAT MAY CAUSE LIFE THREATENING FLASH FLOODS AND
LANDSLIDES. LARGE SWELLS WILL BEGIN TO REACH THE PACIFIC COAST
OF MAINLAND MEXICO...AND THE SOUTHERN PORTION OF THE BAJA
PENINSULA TONIGHT AND FRI. SEE THE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE MONSOON TROUGH EXTENDS FROM 07N77W TO 04N90W TO 07N104W...
THEN RESUMES 12N112W TO 05N120W. ITCZ AXIS FROM 05N120W TO
02N140W. ISOLATED MODERATE TO STRONG CONVECTION NOTED FROM 03N
TO 08N E OF 86W.

...DISCUSSION...

A WEAKENING COLD FRONT EXTENDS SW FROM 29N110W ACROSS THE GULF
OF CALIFORNIA TO 23N120W TO 24N124W TO27N140W. A TROUGH
ORIGINATING FROM THE REMNANTS OF TROPICAL CYCLONE RICK IS
ANALYZED FROM 17N131W TO 20N123.5W. THE STRONG PRESSURE GRADIENT
BETWEEN HIGH PRESSURE BEHIND THE FRONT AND THE TROUGH IS
SUPPORTING A BAND OF STRONG NE 20-25 KT WINDS WITHIN 360 NM NW
OF A LINE FROM 17N132W TO 23N119W WITH COMBINED SEAS OF 8-14 FT
IN NW SWELL. ELSEWHERE THIS LONG PERIOD NW SWELL IS MIXING WITH
NE WIND WAVES AND SE SWELL FROM SANDRA...RESULTING IN COMBINED
SEAS 8-14 FT TO THE N OF LINE FROM 30N116W TO26N116W TO 17N132W
TO 23N140W. ALTHOUGH THE COLD FRONT AND TROUGH SHOULD DISSIPATE
ON FRIDAY...THE PRESSURE GRADIENT WILL INCREASE WITH AN AREA OF
NE-E 20-25 KT ACROSS THE TROPICAL WATERS FROM 16-23N BETWEEN 123-
140W ON FRI...WITH 9-13 FT SEAS PREVAILING...WITH SEAS OF 8-10
FT ACROSS THE WATERS N OF 13N W OF 115W. BY SAT THE AREA OF
ENHANCED NE TRADES WILL SHIFT W TO WITHIN THE AREA FROM 15-19N
BETWEEN 128-140W. THE NW SWELL WILL CONTINUE TO MERGE WITH THE
MIXED SWELL FROM TROPICAL CYCLONE SANDRA...RESULTING IN COMBINED
SEAS OF 7-11 FT WITHIN AN AREA BOUNDED BY LINE FROM 30N140W TO
25N130W TO 29N115W TO 13N115W TO 10N140W TO 30N140W.

GAP WINDS...GULF OF TEHUANTEPEC...THE NORTHERLY WIND FLOW
ACROSSAND DOWNSTREAM OF THE GULF HAS DIMINISHED TO 20-25 KT THIS
AFTERNOON...WITH MAXIMUM SEAS TO 9 FT. EXPECT N-NE SURGES OF 20-
30 KT ACROSS THE GULF WATERS TO AS FAR S AS 13N97W THROUGH
TONIGHT...THEN DECREASING TO 20-25 BY FRIDAY AFTERNOON. COMPUTER
MODEL GUIDANCE SUGGESTS STRONGER DRAINAGE FLOW OF 30 KT LATE SAT
NIGHT INTO SUN MORNING WITH MINIMAL GALE FORCE CONDITIONS
POTENTIALLY DEVELOPING ON SUN NIGHT INTO MON. 

GULF OF PAPAGAYO...A TIGHT PRESSURE GRADIENT ACROSS THE W AND SW
CARIBBEAN WILL CONTINUE TO SUPPORT PULSES OF NE TO E 20-25 KT
WINDS TONIGHT AND AGAIN ON FRI NIGHT ACROSS THE PAPAGAYO REGION
AND DOWNSTREAM TO AROUND 90W...WITH SEAS BUILDING TO 7-8 FT
DOWNSTREAM TO NEAR 09N90W. COMPUTER MODEL GUIDANCE SUGGESTS A
SLIGHTLY STRONGER EVENT ON SAT NIGHT.
 
$$
STRIPLING