000
AXPZ20 KNHC 290356
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT DEC 29 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 1500 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 07N78W TO 07N100W. ITCZ 
CONTINUES FROM 07N100W TO 07N140W. SCATTERED MODERATE CONVECTION 
IS NOTED WITHIN 120 NM S OF MONSOON TROUGH AXIS E OF 
85W...WITHIN 60 NM OF ITCZ AXIS BETWEEN 110W AND 115W...AND 
WITHIN 45 NM N OF AXIS W OF 135W.

...DISCUSSION...

E OF 110W...
A STRONG COLD FRONT IS MOVING THROUGH THE GULF OF MEXICO 
TONIGHT...AND ALREADY EXTENDS FROM THE MOUTH OF THE MISSISSIPPI 
RIVER TO TUXPAN MEXICO. AT THIS RATE...IT WILL PUSH THROUGH THE 
FAR SW GULF OF MEXICO THROUGH SAT MORNING...AND DELIVER A SHOT 
OF WINDS TO GALE FORCE THROUGH THE CHIVELA PASS AND INTO THE 
GULF OF MEXICO BY EARLY AFTERNOON. THE TIMING OF THE ONSET OF 
THE GALE CONDITIONS HAS BEEN ACCELERATED AS A RESULT. GIVEN THE 
STRENGTH OF THE HIGH PRES BEHIND THIS FRONT AND ENHANCED COLD 
AIR ADVECTION...WINDS WILL BE JUST UNDER STORM CONDITIONS BY 
LATE SAT IN THE GULF OF TEHUANTEPEC. IN ADDITION...THE GALE 
CONDITIONS WILL PERSIST THROUGH LATE SUN.

FARTHER SOUTH...WINDS WILL PULSE ACROSS THE GULF OF PAPAGAYO 
OVER THE NEXT COUPLE OF DAYS. WINDS WILL PEAK EACH NIGHT NEAR 25 
KT DURING THE OVERNIGHT AND EARLY MORNING HOURS WITH THE ADDED 
COMPONENT OF NOCTURNAL DRAINAGE FLOW...THEN WILL DIMINISH BELOW 
25 KT DURING THE AFTERNOON AND EARLY EVENING HOURS. 

W OF 110W...
THE UPPER LEVEL PATTERN N OF 25N IS BECOMING MORE AMPLIFIED AS A 
DISTURBANCE FORMS ALONG A DEEP LAYER TROUGH EXTENDING N TO S 
ALONG 125W N OF 25N...DRIFTING EASTWARD. THIS IS AHEAD OF 
RIDGING MOVING E THROUGH 140W. AN ASSOCIATED WEAK COLD FRONT 
EXTENDING FROM OFF NORTHERN CALIFORNIA TO 30N133W 
WILL PUSH SE AND DELIVER AN AREA OF 20 TO 25 KT WINDS TO THE 
DISCUSSION AREA N OF 28N BETWEEN 125W AND 130W BY LATE 
SAT...BEFORE SHIFTING EASTWARD THROUGH NORTHERN BAJA AND THE 
NORTHERN GULF OF CALIFORNIA THROUGH LATE SUN. 

1029 MB HIGH PRES BUILDING N OF THE FRONT HAS TIGHTENED THE PRES 
GRADIENT OVER THE TROPICAL WATERS...ALLOWING A RESURGENCE OF 20 
TO 25 KT TRADE WINDS FROM 10N TO 22N W OF 120W...AS NOTED ON A 
1846 UTC ASCAT PASS. A DEEP LAYER TROUGH DIGGING ACROSS THE N 
CENTRAL PACIFIC INTO THE NE PACIFIC THIS WEEKEND WILL FORCE THE 
SURFACE HIGH PRES SOUTHWARD TO NEAR 30N135W BY LATE SAT. AT THE 
SAME TIME...A SHORTWAVE TROUGH WILL DIG SE IN THE NW FLOW ALOFT 
AND COME INTO PHASE WITH THE DEEP LAYER TROUGH ALONG 125W N OF 
25N. THIS WILL ALLOW A MODEST TROUGH TO MAINTAIN ALONG THE ITCZ 
NEAR 120W. THE AREA OF 20 TO 25 KT WINDS WILL SPREAD SOMEWHAT 
BETWEEN THE TROUGH AND THE HIGH PRES PUSHING SOUTHWARD THROUGH 
SUN.

MEANWHILE NW SWELL WITH 12 TO 16 SECOND PERIODS WILL SWEEP TO 
THE SOUTHEAST OVER MUCH OF THE AREA W OF 110W...MIXING WITH THE 
FRESH NE SWELL IN THE AREA OF 20 TO 25 KT TRADE WINDS. 

$$
CHRISTENSEN