000
AXPZ20 KNHC 180325
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN NOV 18 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 EXTENDS FROM 09N84W TO 06N94W WHERE IT 
TRANSITIONS TO ITCZ...CONTINUING TO 07N115W TO 07N130W TO BEYOND 
07N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED 
FROM 05N TO 09N BETWEEN 122W AND 130W...AND WITHIN 120 NM N OF 
AXIS BETWEEN 130W AND 132W. 

...DISCUSSION...
ALOFT...STRONG W TO SW WINDS 70-90 KT DOMINATE MOST OF THE 
FORECAST AREA N OF 19N. THESE STRONG WINDS ARE NOTED AHEAD OF A 
BROAD UPPER LEVEL TROUGH WITH AXIS CURRENTLY CROSSING THE FAR NW 
PORTION OF THE AREA. THESE WINDS ARE TRANSPORTING ABUNDANT 
MID/UPPER LEVEL MOISTURE ACROSS THE FORECAST REGION FROM THE 
HAWAIIAN ISLANDS TO BAJA CALIFORNIA AND NW MEXICO. SATELLITE 
IMAGERY SHOWS A WIDE BAND OF TRANSVERSE HIGH CLOUDS IN 
ASSOCIATION WITH THESE STRONG WINDS. MEANWHILE...ANTICYCLONIC 
FLOW COVERS MUCH OF THE REGION S OF 19N W OF 100W. THE RIDGE 
EXTENDS FROM A WEAKENING UPPER ANTICYCLONE NEAR 14N108W N-NE 
ACROSS NORTHERN MEXICO INTO TEXAS. BROAD UPPER TROUGH EXTENDING 
FROM A CUT-OFF LOW LOCATED NEAR THE GEORGIA/SOUTH CAROLINA 
BORDER ACROSS THE EASTERN GULF OF MEXICO...AND THE NW CARIBBEAN 
ENTERS THE EASTERN PACIFIC WATERS THROUGH CENTRAL AMERICA NEAR 
11N86W...THEN A TUTT EXTENDS W-SW TO A WEAKENING CYCLONIC VORTEX 
NEAR 06N110W. STRONG SUBSIDENCE AND IMPLIED DRY AIR MASS ALONG 
THE N SIDE OF THIS TUTT IS LIMITING CONVECTION ALONG THE MONSOON 
TROUGH AND THE ITCZ AXIS E OF 110W.  

AT THE SURFACE...A DISSIPATING COLD FRONT ENTERS THE FORECAST 
AREA NEAR 30N120W AND EXTENDS SW TO 25N125W. HIGH PRES IN THE 
WAKE OF THE FRONT IS BUILDING ACROSS THE N PART OF THE AREA THIS 
EVENING. AS A RESULT...THE TRADE WINDS ARE BEGINNING TO INCREASE 
PARTICULARLY FROM 09N TO 17N W OF 125W. EXPECT NE TO E WINDS OF 
20 TO 25 KT WITH BUILDING SEAS OF 8 TO 10 FT ACROSS THIS AREA. 

A SURFACE TROUGH...EMBEDDED IN THE ITCZ...EXTENDS FROM 11N128W 
TO 07N131W. THE MOST RECENT OSCAT PASS SHOWED NE TO E WINDS OF 
20 TO 25 KT ON EITHER SIDE OF THE TROUGH AXIS. THIS FEATURE IS 
PRODUCING SOME SHOWER AND TSTM ACTIVITY FROM 05N TO 09N BETWEEN 
122W AND 130W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE 
THIS CONVECTIVE ACTIVITY.

LONG PERIOD NW SWELL CONTINUES TO PUSH ACROSS THE NW PART OF THE 
REGION WITH COMBINED SEAS TO 9 FT. THIS SET OF NW SWELLS WILL 
CONTINUE TO PROPAGATE S AND E ACROSS THE REGIONAL WATERS OVER 
THE NEXT DAY WITH SEAS CONTINUING TO SLOWLY SUBSIDE. ADDITIONAL 
PULSES OF NW SWELLS WILL ENTER THE NW PART OF THE AREA BY EARLY 
SUN...WITH SEA HEIGHTS REACHING 12 FT ACROSS THE NORTHERN 
FORECAST WATERS...ESPECIALLY N OF 28N. 

GAP WINDS...
PERSISTENT NORTHERLY WINDS 20-30 KT CONTINUE TO BE ENHANCED BY 
NOCTURNAL DRAINAGE FLOW ACROSS THE GULF OF TEHUANTEPEC... 
REACHING MINIMAL GALE FORCE ROUGHLY BETWEEN 0600 AND 1200 UTC. 
THIS GAP WIND FLOW IS EXPECTED TO PERSIST FOR SEVERAL MORE DAYS. 
AT 18/0000 UTC...THE ISSUANCE OF THE HIGH SEAS FORECAST REFLECTS 
THIS ON AND OFF MINIMAL GALE FORCE WIND EVENT. SEE LATEST NHC 
HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS HSFEP2/FZPN03 KNHC. 

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