000
AXPZ20 KNHC 150946 AAA
TWDEP 

TROPICAL WEATHER DISCUSSION...AMENDED GAP WINDS  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN NOV 15 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 07N78W TO 
08N90W TO 09N116W TO 08N130W TO 07N140W. SCATTERED MODERATE 
CONVECTION IS WITHIN 120 NM N OF AXIS FROM 80W TO 95W. ISOLATED 
MODERATE CONVECTION IS WITHIN 210 NM N OF AXIS FROM 101W TO 
109W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS 
WITHIN 270 NM N OF AXIS FROM 112W TO 117W AND WITHIN 300 NM N OF 
AXIS FROM 120W TO 140W.

...DISCUSSION...

A SHARPENING MID TO UPPER LEVEL TROUGH REMAINS THE DOMINANT 
FEATURE ALOFT OVER THE AREA. THIS TROUGH EXTENDS FROM 30N113W TO 
24N120W TO 23N127W AND IS BEING SHIFTED TO THE E BY A STRONG 
UPSTREAM RIDGE MOVING E-SE. CORE SPEEDS WITHIN THE JET OF 110 KT 
ARE AIDING IN THE TRANSPORTATION OF TROPICAL MOISTURE NE INTO A 
DEVELOPING STORM SYSTEM OVER THE U.S. SOUTHERN GREAT PLAINS.
STRONG UPPER LEVEL SUBSIDENCE/DRY AIR ALOFT WAS NOTED IN THE 
WAKE OF THE TROUGH ON WATER VAPOR SATELLITE IMAGERY. 

AT THE SURFACE...A TROUGH EMBEDDED WITHIN THE ITCZ EXTENDS FROM 
15N129W TO 06N132W. SCATTEROMETER DATA CONTINUES TO SHOW A BROAD 
AREA OF 20 TO 25 KT TRADE WINDS GENERALLY FROM 12N TO 25N W OF 
119W ASSOCIATED WITH A TIGHT PRES GRADIENT BETWEEN A 1029 MB 
SURFACE HIGH CENTERED NEAR 35N140W AND THE SURFACE TROUGH/ITCZ. 
THESE TRADE WINDS ARE PRODUCING LOCALLY GENERATED WIND WAVES AND 
THESE WAVES COUPLED WITH PERSISTENT NORTHERLY SWELL IS RESULTING 
IN COMBINED SEAS IN THE 8 TO 13 FT RANGE WHICH WAS CAPTURED BY A 
JASON ALTIMETER PASS A FEW HOURS AGO. THE PRES GRADIENT WILL 
REMAIN TIGHT AS THE HIGH PRES SYSTEM MOVES TO NEAR 32N120W IN 24 
HOURS. THE HIGH WILL THEN WEAKEN BY EARLY TO MID WEEK AS A 
STRONG COLD FRONT APPROACHES THE FAR NW CORNER OF THE AREA.

FARTHER EAST A 0540 UTC ASCAT PASS CAPTURED ANOTHER TROUGH 
EMBEDDED WITHIN THE ITCZ EXTENDING FROM 15N116W TO 08N118W. EVEN 
FARTHER EAST A 0357 UTC QUIKSCAT PASS CAPTURED A BROAD AREA OF 
LOW PRES (NOW HAVING MORE OF AN APPEARANCE OF AN OPEN TROUGH 
COMPARED TO 24 HOURS AGO) NEAR 08N91W. INFRARED SATELLITE 
IMAGERY CONTINUES TO SHOW MINIMAL CONVECTION NEAR THE CENTER OF 
THIS LOW. MODEL GUIDANCE SLOWLY MOVES THIS FEATURE TO THE W  
BRINGING IT TO NEAR 07N94W BY EARLY MON WHILE KEEPING IT FAIRLY
WEAK AROUND 1008 MB. 

...GAP WINDS...AMENDED

THE COMBINATION OF A HIGH PRES RIDGE TO THE W OF THE BAJA 
PENINSULA...A DEVELOPING TROUGH OF LOW PRES ALONG THE E GULF OF 
CALIFORNIA COAST...AND BUILDING HIGH PRESSURE OVER THE U.S. 
GREAT BASIN WILL CREATE A TIGHT PRES GRADIENT WHICH WILL RESULT 
IN INCREASING NW WINDS IN THE GULF OF CALIFORNIA WITHIN 12 
HOURS. DIAGNOSTIC TOOLS FROM AN IN-HOUSE STUDY ON THESE EVENTS 
KEEP WINDS JUST BELOW GALE FORCE ALTHOUGH SUSTAINED WINDS OF 20 
TO 30 KT WITH BRIEF HIGHER GUSTS WILL BE POSSIBLE LATER TODAY 
THROUGH EARLY TUE. THE STRONG NW WINDS WILL THEN GRADUALLY
DIMINISH BY MID WEEK AS THE HIGH PRES RIDGE TO THE WEST WEAKENS.

A STRONG COLD FRONT WILL APPROACH THE S GULF OF MEXICO AND BAY 
OF CAMPECHE LATE MON NIGHT THROUGH TUE. MODEL GUIDANCE PROGS N 
TO NE WINDS IN THE GULF OF TEHUANTEPEC TO INCREASE TO 20 TO 25 
KT AHEAD OF THIS FEATURE BEGINNING JUST BEYOND 48 HOURS. GFS 
ECMWF AND NAM ALL INCREASE WINDS TO GALE FORCE AROUND 72 HOURS 
ALTHOUGH WINDS WILL LIKELY DIMINISH TO BELOW GALE FORCE SHORTLY 
THEREAFTER BY WED NIGHT AS THE FRONTAL BOUNDARY DISSIPATES AND 
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 FROM TUE NIGHT THROUGH WED.

$$
LEWITSKY