000
AXPZ20 KNHC 191517
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAY 19 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...05N77W TO 
07N105W TO 07N115W TO 04N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN 60 NM OF THE POINT 05.5N77.5W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF THE 
POINT 05.5N85.5W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS WITHIN 45 NM EITHER SIDE OF LINE FROM 04N90W TO 
10N98W TO 07N106W. SCATTERED MODERATE TO STRONG CONVECTION IS
WITHIN 120 NM OF THE POINT 11.5N98.5W. SCATTERED MODERATE WITH  
ISOLATED STRONG CONVECTION IS WITHIN THE AREA FROM 06N TO 09N 
FROM 108W TO 111W. SCATTERED MODERATE TO STRONG CONVECTION IS
WITHIN THE AREA FROM 07N TO 09N FROM 113W TO 118W. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN THE AREA FROM 11N TO 15N 
FROM 114W TO 116W.  

...DISCUSSION...

UPPER LEVELS
LARGE MIDDLE AND UPPER TROUGH IS NORTH OF 20N EAST OF 125W AND 
EXTENDS EAST TO ABOUT 110W. THE AREA UNDER THE TROUGH OVER THE 
PACIFIC OCEAN IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER 
LEVELS INDICATING MIDDLE AND UPPER LEVEL MODERATE TO STRONG 
SUBSIDENCE. AN EXCEPTION IS THE AREA EAST OF 118W INCLUDING BAJA 
CALIFORNIA AND THE GULF OF CALIFORNIA WHICH IS DIFFLUENT ALOFT 
WITH AREAS OF MULTI LEVEL CLOUDS WITH SOME ISOLATED EMBEDDED 
CONVECTION. THE TROUGH ALSO EXTENDS SOUTH OF 20N BUT IN A 
NARROWER BAND NORTH OF THE ITCZ BETWEEN 105W AND 118W. THE 
SOUTHEAST HALF OF THIS AREA IS ALSO DIFFLUENT ALOFT WITH MULTI 
LEVEL CLOUDS AND SCATTERED AREAS OF EMBEDDED CONVECTION. THERE 
IS MORE CONVECTION SOUTH OF 20N BECAUSE OF THE WARMER SEA 
SURFACE TEMPERATURES. THE TROUGH IS FORECAST TO MOVE EAST MOVING 
OVER NORTHWEST MEXICO AND SOUTHERN CALIFORNIA WEDNESDAY NIGHT 
AND THURSDAY.

THE AREA WEST OF THE ABOVE TROUGH IS A BROAD SCALE ANTICYCLONIC 
FLOW WITH MOSTLY CLEAR SKIES IN THE MIDDLE AND UPPER LEVELS 
EXCEPT FOR A MOISTURE PLUME FROM 15N TO 23N W OF 130W. SOME 
BROKEN HIGH CLOUDS ARE ASSOCIATED WITH THIS PLUME OF MOISTURE 
THAT EMANATED FROM ITCZ CONVECTION WEST OF THE AREA.

THE TROUGH THAT HAS BEEN OVER THE EASTERN PART OF THE AREA NEAR 
NORTHWEST SOUTH AMERICA HAS MOVED EAST OVER NORTHERN SOUTH 
AMERICA. A BROAD RIDGE NOW OCCUPIES THE AREA EAST OF THE TROUGH 
MENTIONED IN THE FIRST PARAGRAPH. THE RIDGE IS DIFFLUENT ALOFT 
WITH WIDESPREAD MULTI LEVEL CLOUDS WITH EMBEDDED AREAS OF 
CONVECTION.  

SURFACE
WEAKENING SURFACE TROUGH FROM 30N126W TO 23N127W. OTHERWISE A 
WEAK SURFACE RIDGE IS NORTH OF 15N WEST OF 115W. A COUPLE OF 
TROUGHS ARE EMBEDDED WITHIN THE ITCZ ONE ALONG LINE FROM 12N101W 
TO 06N103W...ANOTHER FROM 15N116W TO 09N119W. REMAINDER OF THE 
SURFACE IS ANALYZED AS BROAD TROUGH.
 
GAP WINDS...THE BROAD TROUGH OVER THE WESTERN CARIBBEAN COUPLED 
WITH A RIDGE OVER MEXICO IS RESULTING IN N WINDS 20 TO 35 KT 
ACROSS THE ISTHMUS OF TEHUANTEPEC INTO THE GULF OF TEHUANTEPEC. 
THE GALE FORCE WINDS ARE FORECAST TO END MIDDAY TODAY BUT TO 20 
TO 30 KT WINDS WILL CONTINUE THROUGH TUESDAY NIGHT THEN DIMINISH 
TO LESS THAN 20 KT BY THURSDAY.

$$
LL