000
AXPZ20 KNHC 170328
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT NOV 17 2012

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 06N94W...WHERE IT TRANSITIONS TO 
ITCZ..CONTINUING TO 09N123W TO 08N130W TO BEYOND 08N140W. 
SCATTERED MODERATE FROM 06N TO 10N BETWEEN 117W AND 124W. NO 
SIGNIFICANT CONVECTION ELSEWHERE. 

...DISCUSSION...
ALOFT...A TROUGH/RIDGE/TROUGH PATTERN IS NOTED ACROSS THE 
DISCUSSION AREA. A BROAD UPPER-LEVEL TROUGH COVERS MUCH OF 
THE N WATERS WHILE AN ANTICYCLONIC FLOW DOMINATES MOST OF THE 
REGION S OF 20N W OF 100W...WITH A RIDGE EXTENDING TO THE N-NE 
FROM 15N108W ACROSS BAJA CALIFORNIA AND NW MEXICO INTO THE SW 
CONUS. STRONG W TO SW WINDS ARE NOTED THROUGH THE BASE OF THE 
TROUGH AND OVER THE RIDGE...WITH A WIND MAXIMA OF 110-120 KT 
FROM 25N120W TO 30N118W. THESE WINDS ARE TRANSPORTING ABUNDANT 
MID/UPPER LEVEL MOISTURE ACROSS THE FORECAST REGION. SATELLITE 
IMAGERY SHOWS A WIDE BAND OF TRANSVERSE HIGH CLOUDS IN 
ASSOCIATION WITH THESE STRONG WINDS. BROAD UPPER TROUGH ACROSS 
MOST OF THE EASTERN UNITED STATES...THE GULF OF MEXICO...AND THE 
NW CARIBBEAN ENTERS THE EASTERN PACIFIC WATERS THROUGH NORTHERN 
CENTRAL AMERICA TO NEAR 09N92W. AN ELONGATED TROUGH CONTINUES 
MAINLY WWD FROM THIS POINT TO 06N110W AND THEN SW TO THE EQUATOR 
AT 114W.  

AT THE SURFACE...A 1020 MB HIGH PRESSURE IS CENTERED NEAR 
28N119W. A 1006 MB LOW PRESSURE CENTER IS LOCATED N OF THE AREA 
NEAR 35N127W. THE ASSOCIATED COLD FRONT ENTERS THE FORECAST 
REGION NEAR 30N126W THEN CONTINUES SW TO 24N137W. THE LOW 
PRESSURE CENTER HAS STARTED TO LIFT OUT TO THE NE AND AWAY FROM 
THE FORECAST WATERS. AS A RESULT...WINDS HAVE DIMINISHED TO 20 
KT OR LESS ON EITHER SIDE OF THE COLD FRONT. THE LOW PRES WILL 
DRAG THE ASSOCIATED FRONTAL BOUNDARY EASTWARD OVER THE NEXT 24 
HOURS WHEN THE COLD FRONT IS FORECAST TO DISSIPATE OVER THE 
FORECAST WATERS. HIGH PRESSURE WILL THEN BUILD BACK ACROSS THE N 
PART OF THE AREA BY SUN. BASED ON SCATTEROMETER DATA...THE 
TRADEWINDS REMAIN BELOW 20 KT...BUT THEY ARE EXPECTED TO 
INCREASE TO 20-25 KT LATE SAT INTO SUN AS HIGH PRESSURE BUILDS 
EWD ACROSS THE FORECAST REGION.  

LONG PERIOD NW SWELL ASSOCIATED WITH THE LOW PRESSURE SYSTEM IS 
PUSHING ACROSS THE NW PART OF THE REGION WITH COMBINED SEAS TO 
11 FT. THIS SET OF NW SWELLS WILL PROPAGATE S AND E ACROSS THE 
REGIONAL WATERS OVER THE NEXT DAY WITH SEAS SUBSIDING TO 8-9 FT 
SAT EVENING. ADDITIONAL PULSES OF NW SWELLS WILL ENTER THE NW 
PART OF THE AREA BY EARLY SUN...WITH SEA HEIGHTS OF 12 FT NEAR 
30N. 

GAP WINDS...
A GALE WARNING REMAINS IN EFFECT ACROSS THE GULF OF TEHUANTEPEC. 
MINIMAL GALE FORCE WINDS CONTINUE TO PULSE ACROSS THE AREA 
DURING THE OVERNIGHT AND EARLY MORNING HOURS WITH THE ASSISTANCE 
OF THE NOCTURNAL DRAINAGE FLOW. THIS GAP WIND EVENT IS FORECAST 
TO PERSIST THROUGH AT LEAST SUN MORNING AS A NLY WIND FLOW   
CONTINUES TO BLOW ACROSS THE SW GULF OF MEXICO. 

PULSING OF NOCTURNAL WINDS ARE ALSO EXPECTED ACROSS THE GULF OF 
PAPAGAYO REACHING AROUND 20 KT FROM 0600 TO 1200 UTC...WITH SEAS 
OF 6-7 FT THROUGH AND DOWNWIND OF THE GULF.  

$$
GR