000
AXPZ20 KNHC 092156
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN MAY 09 2010

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...
AXIS ALONG 08N78W TO 05N87W TO 08N114W TO 06N135W TO 04N140W.  
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 150 NM OF 
AXIS W OF 110W.  ISOLATED MODERATE CONVECTION WITHIN 120 NM S OF 
AXIS 84W-89W.    

...DISCUSSION...
UPPER TROUGH EXTENDS S FROM 32N124W TO 10N140W.  TROPICAL 
MOISTURE FROM ITCZ RIDES 6 KT JET CORE NE UNTO BAJA CALIFORNIA 
AND NORTHWESTERN MEXICO AND EVENTUALLY INTO TEXAS.  AIR MASS 
REMAINS FAIRLY DRY W OF TROUGH AXIS DUE TO MODERATE TO STRONG 
SUBSIDENCE.  DOWNSTREAM...MID TO UPPER LEVEL ANTICYCLONIC GYRE 
AT 10N112W HAS BROAD RIDGE EXTEND E TO 105W.  GOOD DIFFLUENT 
FLOW ALOFT ENHANCES SCATTERED MODERATE ISOLATED STRONG  
CONVECTION UNDER GYRE.  

SHARP UPPER LEVEL TROUGH EXTEND FROM 20N105W TO 03N95W WITH VERY 
DRY SUBSIDING AIR MASS WITHIN 6 DEG OF AXIS DUE TO STRONG 
SUBSIDENCE.  FINALLY...SMALL ANTICYCLONIC GYRE AT 03N80W ALSO 
PROVIDING GOOD OUTFLOW FOR SCATTERED CONVECTION ASSOCIATED WITH 
WEAK SURFACE TROUGH PRESENTLY ALONG 78W. 

MODEL GUIDANCE HAVING HARD TIME WITH SURFACE TROUGH ORGANIZATION 
AS GFS PLACES ADVERSE UPPER LEVEL CONDITIONS OVER IT...WHILE 
NOGAPS AND NAM MAINTAIN IT FAVORABLE WITH WEAK CIRCULATION.  
ECMWF TAKES MIDDLE OF THE ROAD APPROACH KEEPING WEAK TROUGH 
MEANDERING IN SE CORNER OF BASIN.   

AT THE SURFACE...HIGH PRES CENTER 1030 MB AT 35N144W DRIFTING SE 
HAS RIDGE EXTEND TO 15N111W.  FRESH NE TRADES ON RIDGE SOUTHERN 
PERIPHERY EXPECTED TO EXPAND IN AREA AND INCREASE TO STRONG 
BREEZE WITH SEAS BUILDING TO 11 FT.  SIMILARLY WINDS ALONG W 
COAST OF BAJA CALIFORNIA DIG S TO 23N BY END OF FORECAST PERIOD.

SURFACE TROUGH EMBEDDED IN ITCZ PREVIOUSLY ALONG 131W HAD 
SURVIVED TOO LONG UNDER HOSTILE ENVIRONMENT ALOFT.  IT FINALLY 
LOST IDENTIFIABLE DEFINITIONS AND DISSIPATED.

GAP WINDS...WITH WEAK TROUGH OVER GULF OF PANAMA AND TIGHT 
GRADIENT ACROSS WESTERN CARIBBEAN...STRONG NE TO E WINDS SEEP 
ACROSS GULF OF PAPAGAYO WITH SEAS TOPPING 10 FT.  WINDS EXPECTED 
TO CONTINUE WELL BEYOND END OF FORECAST PERIOD.

WEAK SURFACE TROUGH OVER BAY OF CAMPECHE FUNNELING FRESH N WINDS 
ACROSS ISTHMUS CAUSING SURGE OF STRONG WINDS ACROSS GULF OF 
TEHUANTEPEC WITH 25 KT WINDS BUILDING SEAS TO 8 FT.  TROUGH 
MOVES W OUT OF AREA MON AND WINDS DIMINISH BELOW 20 KT.  SEAS 
SUBSIDE JUST AS FAST.  

NEW CROSS EQUATORIAL SWELL TRAINS THREATEN E PAC VERY LATE IN 
FORECAST PERIOD AS 10-12 FT COVERING S OF 05N BY END OF FORECAST 
PERIOD...BUT EVENTUALLY SPREADING AS FAR N AS 20N LATER ON. 

$$
WALLY BARNES