000
AXPZ20 KNHC 202202
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI NOV 20 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...ITCZ...
THE ITCZ AXIS EXTENDS FROM 07N77W TO 04N80W TO 06N91W TO 05N106W 
TO 08N119W TO 06.5N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION WITHIN 150 NM S OF AXIS E OF 81W...AND WITHIN 240 NM 
N OF AXIS AND 90 NM S OF AXIS W OF 116W. 

...DISCUSSION...

W OF 115W...A DEEP LAYER TROUGH EXTENDING FROM ALONG THE COASTS 
OF WASHINGTON-OREGON-N CAL TO 23N127W WAS DIGGING E-SE ON THE 
EAST SIDE OF REX BLOCK CENTERED ON THE LARGE RIDGE N OF HAWAII. 
AN ASSOCIATED COLD FRONT EXTENDS FROM NRN CALIFORNIA TO 30N133W 
TO 28N40W AND CONTINUES WWD AS A SHEAR AXIS. THE FRONT WAS 
SHIFTING ESE AND TOWARDS CENTRAL CALIFORNIA AND NE PORTIONS OF 
THE FORECAST AREA. A 1020 MB HIGH NEAR 27N132W WAS 
COLLAPSING...WITH THE STRONGER CENTRAL PACIFIC RIDGE...CENTERED 
ON A 1027 MB SURFACE HIGH ALONG 33N AND N OF HAWAII...WAS 
SLIDING AND BUILDING EWD BEHIND THE COLD FRONT. RECENT 
SCATTEROMETER PASSES SHOW MODERATE TO FRESH 20-25 KT TRADE WINDS 
S OF THE HIGH PRES FROM GENERALLY 20-22N TO THE NRN FRINGES OF 
THE ITCZ ALONG 07.5N FROM 114W WWD BEHIND 140W. THE RESULTANT 
WIND WAVES WERE MIXING WITH A FADING PULSE OF NW SWELL TO 
PRODUCE SEAS OF 8 TO 11 FT N OF 10N AND W OF 115W...WITH SEAS UP 
12 TO 14 FT FROM 17N138W AND DOWNWIND...IN THE STRONGEST NE 
TRADE WIND FLOW. FARTHER E...THE TRADE WIND FLOW HAS DIMINISHED 
SLIGHTLY FROM YESTERDAY AS THE HIGH TO THE NORTH CONTINUES TO 
WEAKEN. THESE FRESH TRADES WILL EXPAND AND SPREAD FARTHER E 
DURING THE NEXT 24 HOURS AS THE CENTRAL PACIFIC HIGH CONTINUES 
TO BUILD E BEHIND THE FRONT N OF THE AREA. THE FRONT ITSELF IS 
EXPECTED TO BECOME DIFFUSE BY SAT NIGHT ACROSS NE PORTIONS OF 
THE AREA AS THE ASSOCIATED UPPER DYNAMICS LIFT OUT. MEANWHILE 
DIVERGENT FLOW ALOFT ON THE RIGHT REAR ENTRANCE AREA OF A WEAK 
JET MAX ON THE SE SIDE OF THE UPPER TROUGH IS INTERACTING WITH 
THE MODEST TRADE WIND CONVERGENCE TO ENHANCE SCATTERED 
CONVECTION N OF THE ITCZ W OF 120W. LOOKING AHEAD THE 
WEEKEND...THE BLOCKING RIDGE N OF HAWAII WILL BREAK DOWN AHEAD 
OF AN APPROACHING CENTRAL PACIFIC TROUGH. THIS WILL ALLOW THE 
SURFACE RIDGE THAT HAS BEGUN TO BUILD BEHIND THE CURRENT 
WEAKENING W COAST COLD FRONT TO REMAIN IN PLACE N OF THE 
AREA...MAINTAINING A BROAD SWATH OF FRESH TO STRONG TRADES FROM 
10N TO 25N W OF 120W. SE CROSS-EQUATORIAL FLOW WILL CONVERGE 
WITH THE NE TRADES TO KEEP CLUSTERS OF CONVECTION ACTIVE ALONG 
THE ITCZ W OF 120W AS WELL. MEANWHILE ANOTHER PULSE OF NW SWELL 
YIELDING COMBINED SEAS OF 10 FT AND GREATER WILL DOMINATE MOST 
OF THE MARINE AREA W OF 115W TONIGHT AND SAT. 

E OF 115W...THE MAIN WEATHER PHENOMENA REMAINS THE PERSISTENT 
CENTRAL AMERICA GAP WINDS. HIGH RESOLUTION SCATTEROMETER DATA 
SHOWED NELY WINDS OF 20 TO 25 KT THROUGH THE GULF OF 
PAPAGAYO...AGAIN THIS MORNING...ENHANCED BY DRAINAGE EFFECTS... 
WITH 20 KT WINDS NOTED OFF OF THE GULF OF FONSECA. FRESH TRADE 
WINDS ARE PUSHING FROM THE SW CARIBBEAN S ACROSS PANAMA AS 
WELL...INTO THE GULF OF PANAMA NEAR 20 KT...ENHANCING MODERATE 
TO STRONG NOCTURNAL CONVECTION OFF THE COLOMBIAN COAST. 
MEANWHILE...SCATTEROMETER DATA ALSO SHOWED NLY FLOW OF 20-25 KT 
PERSISTING TO FLOW S OUT THROUGH THE GULF OF TEHUANTEPEC...BUT 
IS FORECAST TO DIMINISH BRIEFLY THROUGH LATE SATURDAY BEFORE 
POST FRONTAL WINDS ACROSS THE W GULF OF MEXICO FLOW DRAIN 
THROUGH THE PASS AGAIN SUNDAY.

$$

STRIPLING