000
AXPZ20 KNHC 180918
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN DEC 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0700 UTC.

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

THE MONSOON TROUGH AXIS EXTENDS FROM 09N78W TO 09N85W TO 
05N103W. THE ITCZ AXIS LIES FROM 05N103W TO 10N120 TO 06N134W TO 
07N140W. SCATTERED MODERATE CONVECTION IS WITHIN 240 NM EITHER 
SIDE OF THE AXIS E OF 84W AND WITHIN 240 NM EITHER SIDE OF THE 
AXIS BETWEEN 110W AND 127W.

...DISCUSSION...

AN UPPER CYCLONE OVER FAR SW CALIFORNIA AND FAR NW MEXICO WILL 
FINALLY MOVE EASTWARD INTO ARIZONA TODAY. AN ASSOCIATED 1019 MB 
LOW PRES SYSTEM LIES NEAR 30N117W BUT WILL DISSIPATE TODAY AS 
ITS UPPER SUPPORT SHIFTS INLAND. SHOWERS AND THUNDERSTORMS 
ASSOCIATED WITH THE CYCLONE WILL CONTINUE TO IMPACT THE FORECAST 
AREA OVER THE NORTHERN GULF OF CALIFORNIA...BAJA CALIFORNIA 
NORTE AND SONORA TODAY. 

A DISSIPATING COLD FRONT JUST NW OF THE AREA ASSOCIATED WITH A 
WEAKENING DEEP LAYER TROUGH HAS USHERED IN A NEW ROUND OF NW 
SWELL. SHIP ZCDA9 REPORTED 11 FT SEAS NEAR 26N139W AT 0700 UTC. 
THE FRONT SEPARATES A WEAK HIGH PRES SYSTEM JUST N OF THE AREA 
FROM STRONGER HIGH PRES TO IT NW. AS A RESULT OF THE COMPROMISED 
SUBTROPICAL HIGH...TRADE WINDS HAVE SHRUNK WEST OF 135W 
ACCORDING TO THE 0556 UTC ASCAT PASS. THE STRONGER HIGH PRES 
MOVING IN BEHIND THE FRONT WILL MERGE TODAY WITH THE WEAK HIGH 
PRES TO THE E...ALLOWING TRADES TO EXPAND EASTWARD TO 112W 
THROUGH MON MORNING. THE PRES GRADIENT BETWEEN THIS WEAKER 
EASTERN HIGH PRES AND TROUGHING IN THE LEE OF THE SIERRA MADRE 
OCCIDENTAL MOUNTAINS HAS BROUGHT FRESH TO STRONG NW TO N WINDS 
TO THE AREA OFFSHORE OF CABO CORRIENTES...MEXICO. THESE WINDS 
WILL WEAKEN SOMEWHAT AS THE HIGH PRES SYSTEMS MERGE...BUT WILL 
REMAIN FRESH THROUGH AT LEAST EARLY TUE MORNING.

MOISTURE IS POOLED ALONG THE ITCZ/MONSOON TROUGH AXIS WITH 
PRECIPITABLE WATER VALUES HIGHEST ALONG THE EASTERN EDGE OF THE 
AXIS. SHOWERS AND TSTMS LIE OVER PANAMA AND COSTA RICA ALONG THE 
AXIS AND SHOULD CONTINUE FOR THE NEXT DAY OR SO. THIS CONVECTION 
IS DESCRIBED IN THE ITCZ/MONSOON TROUGH AXIS SECTION ABOVE AS 
ARE THE SHOWERS AND THUNDERSTORMS FOCUSED NEAR A WEAK SURFACE 
TROUGH FROM 13N117W TO 07N124W. STRONG UPPER DIFFLUENCE BETWEEN 
AN UPPER LOW NEAR 03N127W AND AN ANTICYCLONE NEAR 10N118W IS 
ENHANCING THE CONVECTION NEAR THE LOW LEVEL TROUGH. THIS PATTERN 
ALOFT WILL BREAK DOWN BY MON...REDUCING THE CHANCE OF 
PRECIPITATION.

GAP WINDS...
GULF OF TEHUANTEPEC...THE 0412 UTC ASCAT PASS CAPTURED WINDS IN 
THE 34-40 KT RANGE IN THE GULF OF TEHUANTEPEC. THE CURRENT GALE 
EVENT IS EXPECTED TO CONTINUE UNTIL MON MORNING WHEN HIGH PRES 
OVER THE SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY SHIFTS 
EASTWARD...REDUCING THE PRES GRADIENT ACROSS SOUTHERN MEXICO 
BETWEEN THIS HIGH AND THE MONSOON TROUGH TO THE S.   

GULF OF PAPAGAYO...THE SAME PRES GRADIENT THAT IS FORCING GALE 
WINDS IN THE GULF OF TEHUANTEPEC IS ALSO YIELDING FRESH TO 
STRONG WINDS IN THE GULF OF PAPAGAYO. THE 0410 UTC ASCAT PASS 
CAUGHT THE FAR WESTERN EDGE OF THE FRESH NE TO E WINDS THAT 
EXTEND FROM PAPAGAYO TO NEAR 09N94W. THESE WINDS WILL BEGIN TO 
DIMINISH OVERNIGHT TONIGHT AS HIGH PRES TO THE N SHIFTS 
EASTWARD...BUT WILL REMAIN FRESH THROUGH AT LEAST TUE MORNING.

$$
SCHAUER