000
AXPZ20 KNHC 202127
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE NOV 20 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 
2100 UTC.

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

THE MONSOON TROUGH IS ALONG 08N78W TO 08N85W TO 05N100W. THE 
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 05N100W TO 
08N125W TO 07N135W TO 08N140W. SCATTERED MODERATE CONVECTION IS 
NOTED WITHIN 60 TO 90 NM EITHER SIDE OF THE ITCZ W OF 115W.

...DISCUSSION...

A PAIR OF MID/UPPER LEVEL SHORT WAVE TROUGH ARE THE MAIN WEATHER 
INFLUENCES N OF 20N. OFF CENTRAL BAJA...A WELL DEFINED MID/UPPER 
LEVEL CYCLONE CENTERED NEAR 25N116W IS MIGRATING EASTWARD INTO 
CENTRAL BAJA. UPPER LIFT AHEAD OF THE CYCLONE IS ENHANCING THICK 
DECKS OF CLOUDINESS OVER THE GULF OF CALIFORNIA AND SOUTHERN 
BAJA...AND SHARPENING RESIDENT TROUGHING OVER NW MEXICO. AT THE 
SURFACE...THE PRES GRADIENT BETWEEN THE TROUGH AND 1024 MB 
SURFACE HIGH PRES CENTERED NEAR 29N127W IS ALLOWING FRESH TO 
STRONG NW WINDS DOWN THE LENGTH OF THE SOUTHERN GULF OF 
CALIFORNIA...AS EVIDENCED BY SHIP OBSERVATIONS AND A 1650 UTC 
ASCAT PASS. SHIP AND ASCAT DATA ALSO INDICATED MODERATE TO FRESH 
NW WINDS ON THE PACIFIC COAST OF THE BAJA PENINSULA...ON THE 
WESTERN EDGE OF THE SURFACE HIGH PRES. 

FARTHER WEST...A SECOND MID/UPPER LEVEL SHORT WAVE TROUGH 
EXTENDS FROM 30N128W TO 24N140W...WITH A WEAK SURFACE 
FRONT/TROUGH IN TOW. THROUGH 48 HOURS...THE SHORT WAVE TROUGH 
OFF BAJA WILL LIFT NE THROUGH ARIZONA...WITH THE SECOND SHORT 
WAVE TROUGH REACHING AS FAR EAST AS 120W. THE 1024 MB SURFACE 
HIGH PRES NEAR 29N127W WILL DISSIPATE IN THE NEXT 24 TO 48 HOURS 
AS THE SHORT WAVE TROUGH PASSES EASTWARD...ALLOWING NW FLOW TO 
DIMINISH OFF BAJA. WINDS OVER THE GULF OF CALIFORNIA WILL 
DIMINISH AS WELL...ALSO DUE IN PART TO WEAKENING HIGH PRES OVER 
THE GREAT BASIN. 

DEEP LAYER RIDGING FOLLOWING THE WESTERN MOST SHORT WAVE TROUGH 
WILL BUILD N OF 30N...AHEAD OF A ANOTHER MORE VIGOROUS LONG WAVE 
TROUGH OVER THE N CENTRAL PACIFIC MOVING INTO THE NE PACIFIC. 
THE REINFORCED SURFACE HIGH PRES WILL ALLOW FRESH TO 
OCCASIONALLY STRONG TRADES IN A BROAD AREA FROM ROUGHLY 12N TO 
22N W OF 120W. COMBINED SEAS OF UP TO 9 FT IN A MIX OF FRESH NW 
AND LONGER PERIOD NW SWELL PERSIST IN THE AREA OF FRESH TO 
STRONG TRADES. ANOTHER ROUND OF NW SWELL IS STARTING TO MOVE 
INTO THE AREA FROM THE N CENTRAL PACIFIC...AND WILL MIX WITH THE 
SUBSIDING SEAS IN THE AREA OF TRADES OVER THE NEXT 48 HOURS.

N WINDS TO 30 KT WERE REPORTED EARLIER THIS MORNING SALINA CRUZ 
NEAR THE PACIFIC TERMINUS OF THE TEHUANTEPEC 
ISTHMUS...SUPPORTING THE CASE FOR GALE CONDITIONS OVER THE GULF 
OF TEHUANTEPEC. THE PRES GRADIENT BETWEEN THE NORTHERN AND 
SOUTHERN ENDS OF THE ISTHMUS IS AROUND 5 MB...ENOUGH TO SUPPORT 
GALE CONDITIONS A LITTLE LONGER...ESPECIALLY DURING THE LATE 
NIGHT AND EARLY MORNING HOURS WHEN DRAINAGE IMPACTS CONTRIBUTE 
TO THE AGGREGATE GAP FLOW. LOOKING AHEAD...WINDS MAY DIMINISH 
BELOW GALE BY THU INTO FRI AS HIGH PRES OVER THE GULF OF MEXICO 
WEAKENS AHEAD OF THE NEXT COLD FRONT. GALES ARE LIKELY AGAIN 
THIS WEEKEND HOWEVER AFTER THE COLD FRONT MOVES INTO THE SW GULF 
OF MEXICO. 

PULSING OF NOCTURNAL WINDS ARE ALSO EXPECTED TO CONTINUE ACROSS 
THE GULF OF PAPAGAYO...WITH WINDS TO 25 KT AND SEAS OF 8-9 FT 
THROUGH LATER THIS AFTERNOON...THEN WILL DIMINISH TO 20 KT OR 
LESS WITH ANOTHER SURGE FORECAST BY THU MORNING.

$$
CHRISTENSEN