000
AXPZ20 KNHC 200926
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN MAY 20 2007

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 
0845 UTC.

...ITCZ...

INTERTROPICAL CONVERGENCE ZONE ALONG 7N77W 9N90W 6N102W 7N122W 
6N131W 6N140W. CLUSTERS OF STRONG CONVECTION WITHIN 45 NM OF 
4N78W 11N88W 12N88W 7N93W 6N102W AND 9N109W. ISOLATED MODERATE 
NEAR 6N83W 8N84W 8N106W 5N138W AND 8N140W. SCATTERED MODERATE 
WITHIN 30 NM OF A LINE FROM 7N111W TO 9N122W AND FROM 9N130W TO 
8N134W. 

...DISCUSSION...

A WELL DEFINED SHORTWAVE TROUGH WAS OFF THE NW COAST OF BAJA 
TONIGHT. GFS MODEL WASN'T SHOWING THE VORTICITY PATTERN QUITE 
CORRECT. LATEST WATER VAPOR SHOWS BEST ROTATION NEAR 31N119W 
WHILE GFS SHOWS VORT CENTERS NEAR 31N111W AND 31N120W. THE 
SHORTWAVE HAS BEEN VIRTUALLY STUCK AT THIS LOCATION THE PAST 48 
HRS BUT HAS BEEN GAINING SOME AMPLITUDE AS IT TAPS THE NRN 
BRANCH OF THE WESTERLIES. AND IT'S DOING THIS BECAUSE A MID 
LEVEL RIDGE IS BUILDING ALONG 135W. THE OTHER MID LEVEL RIDGE 
ALONG 105W HAS BEEN SLOWLY ERODING AND WILL EVENUALLY ALLOW THE 
SHORTWAVE TO MOVE EWD. ON THE SURFACE TONIGHT A 1029 MB HIGH 
CENTER ANCHORES THE PACIFIC RIDGE. THE HIGH IS NEAR 29N138W WITH 
A RIDGE SE TO 15N105W. THE RIDGE IS PRODUCING NE TRADES 20 TO 25 
KT S OF 20N W OF 125W. WINDS ALONG THE BAJA COAST ARE NWLY NEAR 
20 KT ACCORDING TO SSMI AND QUIKSCAT..SLIGHTLY HIGHER THAN THE 
GFS MODEL 06Z VALUES. NW SWELL 6 TO 8 FT ALONG THE BAJA COAST 
WITH VALUES TO 9 FT N OF 27N. GAP WINDS MOSTLY LIGHT. NO 
AVAILABLE PASSES FROM SSMI AND QUIKSCAT TONIGHT FOR TEHUANTEPEC 
BUT GFS FORECASTS ONLY LIGHT WINDS.

LATER DAY 1 THE GFS MODEL SHOWS THE MID LEVEL RIDGE ALONG 135W 
BULGING NWD..TAPPING MORE AVAILABLE ENERGY FROM THE NRN BRANCH 
INTO THE SHORTWAVE WHICH CONTINUES ALONG 115W. ON THE SURFACE 
LATER DAY 1 THE GFS MODEL SHOWS SOME DECREASE IN NW WINDS ALONG 
THE BAJA COAST. THOUGH THE PACIFIC RIDGE REMAINS 
UNCHANGED..SURFACE PRESSURES OVER THE GULF OF CORTEZ RISE AND 
THIS WOULD RELAX THE PRESSURE GRADIENT ALONG THE COAST. STILL NW 
SWELL OF 6 TO 8 FT CAN BE EXPECTED ALONG THE COAST. LITTLE 
CHANGE TO NE TRADES AND GAP WINDS REMAIN LIGHT. SOME INCREASE IN 
SW WINDS S OF 5N E OF 100W..POSSIBLY DUE TO SLIGHTLY LOWER 
PRESSURES IN THE MONSOON TROUGH.

FOR DAY 2 THE SHORTWAVE ALONG 115W BEGINS TO MOVE EWD AS MID 
LEVEL HEIGHTS FALL OVER THE WRN CONUS. ALSO THE RIDGE ALONG 135W 
CONTINUES BUILDING NWD WHICH CONTINUES TO TAP ENERGY FROM THE 
NRN BRANCH. THE SRN BRANCH ALONG 20N REMAINS WEAK ALTHOUGH SOME 
WEAK IMPULSES MIGRATE EWD ACCORDING TO GFS. ON THE SURFACE DAY 2 
THE PRESSURE GRADIENT RELAXES E OF 125W AS THE PACIFIC RIDGE 
RE-0RIENTS ITSELF MORE N/S W OF 125W. NE TRADES REMAIN ABOUT THE 
SAME BUT WINDS ALONG THE BAJA COAST SHOULD BE MOSTLY 10 TO 15 
KT. NW SWELL OF 7 TO 10 FT WILL CONTNUE THOUGH DUE TO STRONGER 
WINDS N OF 30N ALONG THE CA COAST. GAP WINDS REMAIN MOSTLY LIGHT 
WHILE SW WINDS S OF 4N E OF 100W DECREASE SLIGHT TO MOSTLY 15 TO 
20 KT WITH SW SWELL TO 8 FT.  

$$
RRG