000
AXPZ20 KNHC 060929
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU DEC 06 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

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

MONSOON TROUGH EXTENDS FROM 09N84W TO 07N93W WHERE IT 
TRANSITIONS TO THE ITCZ EXTENDING TO 09N118W TO BEYOND 07N140W. 
SCATTERED MODERATE CONVECTION IS NOTED FROM 06N TO 10N BETWEEN 
103W AND 111W. SIMILAR CONVECTION CAN BE FOUND FROM 08N TO 12N 
BETWEEN 111W AND 120W...AND WITHIN 60 NM EITHER SIDE OF ITCZ 
AXIS BETWEEN 128W AND 133W.

...DISCUSSION...

ALOFT...A RIDGE/TROUGH/RIDGE PATTERN DOMINATES MOST OF THE 
REGIONAL WATERS. AN UPPER-LEVEL TROUGH EXTENDS FROM 25N125W TO 
14N127W THEN CONTINUES SE TO NEAR 06N118W. BROAD RIDGING COVERS 
THE AREA TO THE E OF THE TROUGH TO ACROSS CENTRAL AMERICA AND 
NRN S AMERICA. DIFFLUENT FLOW IS EVIDENT TO THE E OF THE 
TROUGH...AND IS ENHANCING THE CONVECTION PREVIOUSLY DESCRIBED. 
AN AREA OF INCREASED MULTILAYERED CLOUDINESS WITH LIKELY 
EMBEDDED SHOWERS IS ALSO NOTED AHEAD OF THE TROUGH AXIS. WATER 
VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE MAINTAINING 
DRY AND STABLE CONDITIONS ACROSS MOST OF THE AREA N OF 10N AND W 
OF THE TROUGH. SOME MID/UPPER LEVEL MOISTURE IS CURRENTLY 
REACHING THE FAR NW CORNER OF THE FORECAST REGION AHEAD OF 
ANOTHER UPPER CYCLONE FORECAST TO DROP SE INTO THE DISCUSSION 
AREA ON FRI...BUT ITS ASSOCIATED SURFACE FRONTAL SYSTEM SHOULD 
REMAIN NW OF THE AREA.

AT THE SURFACE...A 1025 MB HIGH PRES IS ANALYZED AT 27N136W WITH 
A RIDGE EXTENDING SE TO NEAR 21N115W. ONCE AGAIN...SCATTEROMETER 
DATA PROVIDED OBSERVATIONS OF 20-25 KT TRADE WINDS ON THE 
SOUTHERN PERIPHERY OF THE RIDGE...PARTICULARLY FROM 07N TO 21N W 
OF 125W. SEA HEIGHTS WITHIN THE AREA OF THE TRADES ARE 8-10 FT 
IN MIXED SHORT PERIOD NE AND LONG PERIOD NW SWELL. MODERATE TO 
FRESH NLY WINDS ARE NOTED BETWEEN THE RIDGE AND THE SEMI- 
PERMANENT TROUGH ACROSS WESTERN MEXICO. THE 0532 UTC ASCAT PASS 
CONFIRMED THE PRESENCE OF THESE WIND SPEEDS. THE SURFACE HIGH IS 
FORECAST TO MOVE SW WHILE WEAKENING TODAY. AS A RESULT...THE 
AREA OF TRADES WILL SHRINK TO 07-20N W OF 130W TONIGHT...AND 
WINDS ARE FORECAST TO DIMINISH TO 20 KT OR LESS FRI NIGHT WITH 
SEAS SUBSIDING TO 7-8 FT IN THE NE SWELL. THE GRADIENT WILL 
TIGHTEN NE OF THE SURFACE RIDGE...GENERALLY TO THE N OF 28N 
BETWEEN 118-128W...TONIGHT AS A LARGE AND STRONG AREA OF HIGH 
PRES BUILDS S INTO THE FORECAST AREA BY FRI. THE GRADIENT WILL 
SUPPORT NW WINDS OF 15-20 KT OFF THE NORTHERN COAST OF BAJA 
CALIFORNIA WITH SEAS OF 7-9 FT IN NW SWELL. 

GAP WINDS...
N TO NE WINDS AT 20-30 KT ARE SURGING THROUGH THE CHIVELA PASS 
AND IN AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC. THESE WINDS 
WILL BE RATHER SHORT-LIVED AS MODEL GUIDANCE FORECASTS THEM TO 
DIMINISH TO 20-25 KT LATER THIS MORNING AND TO 20 KT OR LESS BY 
THIS EVENING.

WINDS WILL CONTINUE TO PULSE IN THE GULF OF PAPAGAYO TO 20 KT 
DURING LATE NIGHT AND EARLY MORNING HOURS THEN DIMINISH BELOW 15 
KT IN THE AFTERNOON THROUGH SAT.  

$$
GR