000
AXPZ20 KNHC 232143
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN DEC 23 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 06N77W TO 04N82W TO 
06N89W...WHERE IT TRANSITIONS TO THE ITCZ AND EXTENDS THROUGH 
06N110W TO 08N118W TO 07N140W. SCATTERED MODERATE CONVECTION WAS 
WITHIN 90 NM OF THE ITCZ BETWEEN 95W AND 110W. 

...DISCUSSION...

LARGE MID-TO UPPER LEVEL ANTICYCLONE CENTERED NEAR THE COAST OF 
MEXICO AT 17N100W DOMINATES THE FLOW OVER THE EAST PACIFIC E OF 
130W. AN UPPER LEVEL TROUGH/SHEAR AXIS EXTENDS FROM THE FAR NW 
CORNER OF BAJA CALIFORNIA WSW THROUGH 27N127W 22N135W THROUGH 
17N140W. STRONG WSW FLOW BETWEEN THE TWO FEATURES WITHIN THE 
AXIS OF A VERY STRONG SUBTROPICAL JETSTREAM WAS TRANSPORTING
COPIOUS AMOUNTS OF MID TO UPPER LEVEL MOISTURE NE ACROSS BAJA 
CALIFORNIA...NORTHERN OLD MEXICO INTO THE SOUTHERN GREAT PLAINS 
OF THE U.S. AND WAS FUELING MID-LATITUDE CYCLOGENESIS OVER THE 
CONUS. THE CORE OF THE JETSTREAM WITH SATELLITE DERIVED WINDS IN 
EXCESS OF 150 KT EXTENDED FROM THE BASE OF THE AFOREMENTIONED 
TROUGH NEAR 16N135W THROUGH 24N130W 30N115W ACROSS NORTHERN 
TEXAS.  

AT THE SURFACE...SUBTROPICAL RIDGE FROM 30N122W TO 24N140W 
REMAINS PRIMARY SYNOPTIC FEATURE IN THE REGION. 1710 AND 1850 
UTC ASCAT PASSES SHOWED A LARGE AREA OF FRESH 20-25 KT NE TRADE 
WINDS S OF THE RIDGE...WITH HIGHEST WINDS AND SEAS FROM 08N TO 
19N W OF 125W. LARGE LONG PERIOD NW SWELL UP TO 20-21 SECONDS 
CONTINUES TO SWEEP SOUTHWARD OVER THE DISCUSSION AREA AND NOW 
EXTENDING INTO THE SOUTHERN HEMISPHERE...WITH COMBINED SEAS TO 
14 FT W OF 110W. EAST OF 110W MERGING NE SWELL GENERATED BY HIGH 
WINDS NEAR THE GULFS OF PAPAGAYO AND TEHUANTEPEC...AS WELL AS 
FONSECA TO LESSER EXTENT...ARE CREATING A LARGE AREA OF 8-12 FT 
SEAS S OF 14N.

SUBTROPICAL RIDGE WILL REMAIN ANCHORED ALONG 27N THROUGH TUE 
NIGHT WHILE A WEAKENING COLD FRONT MOVES EASTWARD N OF 30N. THE 
TRAILING EDGE OF THE FRONT WILL AFFECT THE FAR NE PORTION OF THE 
AREA WED INTO WED NIGHT. STRONGER WINDS N OF THE AREA WILL 
RESULT IN 10-11 FT SEAS PUSHING INTO PORTIONS N OF 25N BY THU. 
STRONG HIGH PRES THAT DEVELOPS BEHIND THE FRONT NEAR 35N140W WED 
SHIFTS SLOWLY SOUTHEAST THROUGH FRI AS ANOTHER CENTRAL PACIFIC 
COLD FRONT PUSHES EASTWARD N OF 30N. THE ITCZ WILL REMAIN 
SITUATED ALONG 8N/9N THROUGH FRI...SUPPORTING MODERATE TO FRESH 
NE TRADE WINDS S OF THE SUBTROPICAL RIDGE FROM 09N TO 20N W OF 
110W THROUGH WED THEN SHIFT FURTHER WEST WED NIGHT THROUGH FRI 
AS THE RIDGE WEAKENS.

GAP WINDS...
A 1528 UTC ASCAT PASS INDICATED 30+ KT WINDS IN THE GULF OF 
TEHUANTEPEC...AND GIVEN THE LOW BIAS OF THE ASCAT GALE FORCE 
WINDS LIKELY WERE STILL OCCURRING AT THAT TIME. SINCE THEN 
OBSERVATIONAL AND NWP MODEL GUIDANCE SUGGESTS WINDS HAVE DROPPED 
BELOW GALE FORCE AS OF 1800 UTC. AS SOUTHERLY RETURN FLOW 
INCREASES IN THE GULF OF MEXICO TONIGHT AND MON THIS WILL HASTEN 
THE END OF THE GAP WIND EVENT ALTOGETHER WITH WINDS EXPECTED TO 
QUICKLY DROP BELOW 20 KT BY EARLY MON.    

FURTHER SOUTH...A 1718 UTC OSCAT PASS INDICATED 25-30 KT WINDS 
IN THE GULF OF PAPAGAYO AND A SEPARATE AREA OF WINDS IN THE GULF
OF FONSECA AS WELL. THESE WINDS ARE EXPECTED TO GRADUALLY 
DECREASE OVER THE NEXT 24 TO 36 HOURS. 

$$
COBB