000
AXPZ20 KNHC 172201
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 UTC TUE FEB 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC. 
  
...SPECIAL FEATURES...

GULF OF TEHUANTEPEC GALE WARNING...STRONG SURFACE HIGH PRESSURE 
WILL BUILD INTO SOUTHERN MEXICO BEHIND A COLD FRONT THAT IS 
MOVING ACROSS THE GULF OF MEXICO. THE TIGHT SURFACE PRESSURE 
GRADIENT ALONG WITH A PUSH OF DENSE DRY AND COOL AIR THROUGH THE 
CHIVELA PASS IN SOUTHERN MEXICO WILL RESULT IN WINDS TO GALE 
FORCE IN THE GULF OF TEHUANTEPEC STARTING LATE TONIGHT. 

RECENT OBSERVATIONS FROM THE COAST OF VERACRUZ IN THE SW GULF OF 
MEXICO INDICATE PEAK WINDS TO 38 KT SO FAR. IN 
ADDITION...MINATITLAN (MMMT) ON THE NORTHERN END OF THE ISTHMUS 
OF TEHUANTEPEC INDICATED GUSTS TO 35 KT...AN INDICATION OF THE 
GRADIENT FLOW ALREADY ENTERING INTO THE GAP. THIS WILL MIX TO 
THE SURFACE LATER TONIGHT OVER THE GULF OF TEHUANTEPEC.

THE SEA HEIGHTS WILL BUILD DOWNSTREAM OF THE GULF OF 
TEHUANTEPEC...REACHING AS HIGH AS 16 FEET BY LATE WEDNESDAY. THE 
GALE-FORCE WINDS WILL PERSIST THROUGH LATE THU...AND THEN 
DIMINISH AS THE HIGH PRESSURE TO THE N OF THE AREA WEAKENS AND 
SHIFTS EASTWARD.
                   
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM 10N85W TO 03N95W...WHERE IT 
TRANSITIONS TO THE ITCZ. THE ITCZ CONTINUES WEST FROM 03N95W TO 
06N1125W TO 05N135W TO BEYOND 06N140W. NUMEROUS MODERATE TO 
ISOLATED STRONG CONVECTION FROM 06N TO 14N BETWEEN 118W AND 
130W. 

...DISCUSSION... 

A CUTOFF MID TO UPPER LOW IS CENTERED NEAR 22N133W WITH A TROUGH 
REACHING SOUTH 05N130W. THE CUT LOW IS THE SOUTHERN REMNANT OF 
AN UPPER TROUGH THAT MOVED THROUGH THE REGION YESTERDAY BUT HAS 
MOSTLY LIFTED NE OF THE AREA. THIS WAS SUPPORTING A COLD FRONT 
THAT HAS SINCE STALLED FROM 30N134W TO 25N137W...AND IS STARTING 
TO DISSIPATE. SHIP OBSERVATIONS AND SCATTEROMETER DATA INDICATE 
MODEST WINDS NEAR THE FRONT...BUT A PAIR OF ALTIMETER SATELLITE 
PASSES NEAR THE FRONT CONFIRM WAVE HEIGHTS OF 8 TO 12 FT. THIS 
IS DUE TO LONG PERIOD SWELL FROM THE NORTHWEST. THIS IS FORECAST 
TO DECAY TO 8 FT AS IT PROPAGATES SE AND SHRINK IN AREAL 
EXTENT...BUT WILL MIX WITH SHORTER PERIOD TRADE WIND SWELL FROM 
08N TO 14N BETWEEN 120W AND 127W THROUGH 48 HOURS.

DIVERGENCE ALOFT ASSOCIATED WITH THE UPPER TROUGH...IN CONCERT 
WITH TRADE WIND CONVERGENCE AT THE SURFACE...IS SUPPORTING 
NUMEROUS MODERATE TO STRONG THUNDERSTORMS OVER THE WATERS FROM 
06N TO 14N BETWEEN 118W AND 130W. A SURFACE TROUGH IS EMBEDDED 
IN THE CONVECTION...REACHING FROM 10N125W TO 04N125W. A PAIR OF 
TOGA-TAO BUOYS IN THE VICINITY OF THE TROUGH INDICATE TRADE 
WINDS TO 20 KT. THE UPPER FEATURES WILL WEAKEN GRADUALLY BUT 
REMAIN GENERALLY IN PLACE THROUGH THE NEXT 24 TO 48 HOURS. THIS 
WILL KEEP THE SURFACE TROUGH IN PLACE AS WELL. THE SUBTROPICAL 
RIDGE WILL STRENGTHEN BY THU MORNING...ALLOWING FOR A SLIGHTLY 
TIGHTER GRADIENT BETWEEN THE TROUGH AND THE RIDGE...ENHANCING 
TRADE WIND FLOW SOMEWHAT FROM 10N TO 20N BETWEEN 120W AN 130W. 

$$
CHRISTENSEN