000
AXPZ20 KNHC 130318
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN NOV 13 2011

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.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH FROM 09N84W TO 06N88W TO 07N94W. ITCZ AXIS FROM 
07N94W TO 09N124W WHERE IT IS DISRUPTED BY A TROUGH FROM 12N126W 
TO 07N130W. THERE IS SCATTERED MODERATE CONVECTION NOTED S OF 
09W WITHIN 90 NM W OF TROUGH. THE ITCZ THEN RESUMES FROM 
06.5N135W TO 07.5N140W. NO SIGNIFICANT CONVECTION WAS NOTED WITH 
THE ITCZ OR MONSOON TROUGH.

...DISCUSSION...

STRONG HIGH PRESSURE 1032 MB CENTERED NEAR 37N152W HAS RIDGE 
EXTENDING SE TO NEAR 19N128W. LOW PRESSURE 1006 MB IS CENTERED 
NEAR 30N121W. THIS AFTERNOONS ASCAT PASS INDICATED GALE FORCE 
WINDS OVER THE SW QUADRANT OF THIS LOW DUE TO A TIGHT PRESSURE 
GRADIENT BETWEEN THIS LOW AND THE AFOREMENTIONED RIDGE...AND A 
GALE WARNING IS IN EFFECT FOR THIS AREA. THIS IS A GREAT EXAMPLE 
OF THE BENEFIT OF SATELLITE SCATTEROMETER DERIVED WINDS...AS 
WITHOUT THIS WELL PLACED ASCAT PASS EVIDENCE OF THE GALE FORCE 
WINDS WOULD HAVE FALLEN BETWEEN THE SPARSE OCEANIC OBSERVATIONS. 
WINDS ARE EXPECTED TO DIMINISH BELOW GALE FORCE SUN AFTERNOON AS 
THE LOW PRESSURE CENTER FILLS. 

THE PRESSURE GRADIENT BETWEEN THE RIDGE MENTIONED ABOVE AND THE 
ITCZ HAS BROUGHT A RETURN TO FRESH 20 KT TRADES FROM 12N TO 18N 
W OF 132W AS DEPICTED BY THIS AFTERNOONS ASCAT PASS. THIS AREA 
OF TRADES WILL LINGER THROUGH THE FORECAST PERIOD. THERE IS ALSO 
A TIGHT PRESSURE GRADIENT BETWEEN THE LOW PRESSURE MENTIONED 
ABOVE AND HIGH PRESSURE OVER THE GREAT BASIN REGION OF THE 
UNITED STATES. THIS GRADIENT IS MAINTAINING FRESH TO STRONG S TO 
SW WINDS OVER THE FAR N PART OF THE GULF OF CALIFORNIA. THESE 
WINDS ARE EXPECTED TO DIMINISH BELOW 20 KT BY SUN MORNING AS THE 
LOW FILLS.  

NW SWELLS WITH COMBINED SEAS TO 17 FT PREVAIL OVER THE ENTIRE NW 
PART OF THE AREA. THE NW SWELL WILL SPREAD SE AND ENCOMPASS MUCH 
OF THE AREA W OF 11OW OVER THE NEXT 48 HOURS...ALTHOUGH OVERALL 
SEA HEIGHTS WILL SUBSIDE TO NO MORE THAN 10 FT AS THE SWELL 
DECAYS. 

WINDS HAVE DIMINISHED BELOW 20 KT OVER THE GULF OF TEHUANTEPEC. 
THE NE SWELL GENERATED FROM THE TEHUANTEPEC EVENT ARE REACHING 
AS FAR E AS 108W. THIS SWELL WILL CONTINUE TO SUBSIDE...AND 
COMBINED SEAS WILL FALL BELOW 8 FT BY SUN EVENING. 

GULF OF PAPAGAYO...ENHANCED GRADIENT FLOW OVER THE SW CARIBBEAN 
ALONG WITH OVERNIGHT DRAINAGE EFFECTS OFF THE HIGH TERRAIN OF 
NORTHERN COSTA RICA MAY ALLOW WINDS TO 20 KT THROUGH THE GULF OF 
PAPAGAYO DURING THE LATE NIGHT AND EARLY MORNING THROUGH 48 
HOURS.  

S OF PANAMA...THE FAVORABLE INTERACTION OF A MID LEVEL TROUGH 
DEFORMATION WITH THE MONSOON TROUGH OVER THE SW CARIBBEAN HAS 
RESULTED IN AN ACTIVE MONSOON TROUGH OVER THIS AREA. BACKGROUND 
FLOW OVER THIS AREA IS CURRENTLY...AND WILL REMAIN...FAVORABLE 
FOR THIS ACTIVITY TO CONTINUE WHILE SLOWLY SPREADING WESTWARD 
OVER THE NEXT DAY OR SO WITH THE POSSIBLE FORMATION OF A LOW 
PRESSURE CENTER WITHIN THE MONSOON TROUGH. THE ACTIVE MONSOON 
TROUGH HAS RESULTED IN ENHANCED SW MONSOONAL FLOW S OF 
PANAMA...WHICH WILL SPREAD WESTWARD OVER THE NEXT COUPLE OF 
DAYS. 

$$
AL