000
AXPZ20 KNHC 160921
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON NOV 16 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG A LINE FROM
06N77W TO 07N95W TO 10N121W TO 10N133W TO 08N140W. SCATTERED 
MODERATE CONVECTION CAN BE FOUND WITHIN 60 NM EITHER SIDE OF THE 
ITCZ AXIS BETWEEN 108W AND 110W AND WITHIN 150 NM S OF THE ITCZ 
AXIS BETWEEN 114W AND 118W AND WITHIN 180 NM S OF THE ITCZ AXIS 
BETWEEN 123W AND 132W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION CAN BE FOUND WITHIN 180 NM N OF THE ITCZ AXIS BETWEEN 
120W AND 124W AND BETWEEN 128W AND 134W. 

...DISCUSSION...

A MID TO UPPER LEVEL TROUGH EXTENDS FROM CENTRAL TEXAS SOUTHWEST 
-WARD THROUGH THE S HALF OF THE BAJA PENINSULA TO 20N120W AND TO 
21N130W AS INDICATED BY WATER VAPOR SATELLITE IMAGERY. AN UPPER 
JET LIES JUST TO THE E OF THE TROUGH AXIS WITH SW TO W WINDS OF 
80 TO 85 KT IN THE JET CORE ENHANCING CONVECTION FROM THE ITCZ 
NE TO CENTRAL MEXICO. MEANWHILE CONFLUENT FLOW NW OF THE TROUGH 
AXIS MAINTAINS A VERY DRY AIR-MASS N OF 20-21N BETWEEN 110W AND 
135W. 

THIS TROUGH WILL GRADUALLY SHIFT TO THE E OVER THE NEXT FEW DAYS 
AS A DEEP LAYER RIDGE OF HIGH PRES OVER THE NW WATERS AND AN 
ATTENDANT SURFACE HIGH OF 1026 MB SHIFTS FROM NEAR 32N130W TO 
NEAR 31N132W WITH A STRONG COLD FRONT APPROACHING THE NW CORNER
OF THE WATERS BY EARLY TUE. AHEAD OF THIS FRONT A TIGHT PRES 
GRADIENT BETWEEN THE HIGH AND THE ITCZ WILL REMAIN IN PLACE
GENERALLY W OF 116W WITH A LARGE AREA OF NE TO E TRADES IN THE 
20 TO 25 KT RANGE PERSISTING THROUGH MID WEEK. THE SWATH OF 
THESE STRONGER WINDS WILL SLOWLY SHIFT TO THE S THROUGH THE END 
OF THE WEEK AS THE COLD FRONT MOVES INTO THE N WATERS BEFORE 
EVENTUALLY DISSIPATING. MEANWHILE NORTHERLY SWELLS COMMINGLING 
WITH LOCALLY GENERATED WIND WAVES WILL RESULT IN COMBINED SEAS 
OF 8 TO 12 FT OVER THIS SAME AREA. A NEW SET OF NW SWELL OF 8 TO 
15 FT WILL ARRIVE BEHIND THE COLD FRONT TUE NIGHT PROPAGATING 
THROUGH THE N WATERS THROUGH THE REMAINDER OF THE WEEK.

OTHERWISE...TWO TROUGHS OF LOW PRES EXIST AT THE SURFACE 
EMBEDDED IN THE ITCZ...ONE FROM 14N122W TO 07N125W AND THE OTHER 
FROM 14N132W TO 07N135W. A WEAK AREA OF LOW PRES NEAR 07N96W IS 
ALSO EMBEDDED IN THE ITCZ. INFRARED SATELLITE IMAGERY INDICATES 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION OCCURRING IN 
THE VICINITY OF EACH OF THESE FEATURES. MODEL GUIDANCE WEAKENS 
THE LOW INTO AN OPEN TROUGH WITHIN 24 HOURS WHILE IT CONTINUES 
TO SLOWLY PROGRESS TO THE W THROUGH THE NEXT SEVERAL DAYS. 

GAP WINDS...

A TIGHT PRES GRADIENT EXISTS OVER THE GULF OF CALIFORNIA DUE TO 
THE COMBINATION OF A HIGH PRES RIDGE TO THE W OF THE BAJA 
PENINSULA...A TROUGH OF LOW PRES ALONG THE E GULF OF CALIFORNIA 
COAST...AND BUILDING HIGH PRESSURE OVER THE U.S. GREAT BASIN. AS 
A RESULT N TO NW WINDS IN THE GULF OF CALIFORNIA OF 20 TO 30 KT 
ARE EXPECTED TO CONTINUE THROUGH TONIGHT. THE STRONG WINDS WILL 
GRADUALLY DIMINISH BY EARLY TUE AS THE HIGH PRES RIDGE TO THE 
WEST WEAKENS.

A STRONG COLD FRONT ASSOCIATED WITH THE AFOREMENTIONED UPPER 
TROUGH MOVING SE INTO MEXICO WILL APPROACH THE S GULF OF MEXICO 
AND BAY OF CAMPECHE LATE TONIGHT. N TO NE WINDS WILL FUNNEL 
THROUGH THE ISTHMUS OF TEHUANTEPEC AND WILL INCREASE TO 20 TO 30 
KT IN THE GULF OF TEHUANTEPEC BY LATE TONIGHT. MANY OF THE 
FORECAST MODELS CONTINUE TO ALLOW THE WINDS TO REACH GALE FORCE 
THERE TUE MORNING THROUGH TUE NIGHT AND HAVE ACCORDINGLY ISSUED 
A GALE WARNING. WINDS WILL DIMINISH TO BELOW GALE FORCE ON WED 
AS THE PRES GRADIENT WEAKENS.

IN ADDITION...NE TO E WINDS IN THE 20 TO 25 KT RANGE WILL BE 
POSSIBLE IN THE GULF OF PAPAGAYO BY TUE NIGHT.

$$
LEWITSKY