000
AXPZ20 KNHC 171517
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAY 17 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 
0915 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...04N77W TO 
09N100W TO 07N140W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS WITHIN 30 NM OF THE POINT 07N83W AND ALSO THE 
POINT 04N86W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF 
THE POINT 11.5N100.5W. SCATTERED MODERATE TO STRONG CONVECTION 
IS WITHIN 90 NM OF THE POINT 14.5N112.5W. SCATTERED MODERATE 
CONVECTION IS WITHIN 90 NM OF THE POINT 10N115W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN 90 NM OF THE 
POINT 06N117.5W.

...DISCUSSION...

WEAK RIDGE IS OVER THE FAR NORTHWEST PART OF THE AREA NORTHWEST 
OF A LINE THROUGH 32N130W TO 23N140W. THIS FEATURE IS FORECAST 
TO PERSIST FOR THE NEXT SEVERAL DAYS. MIDDLE AND UPPER LEVELS 
ARE MOIST BUT CLOUD FREE.

ELSEWHERE NW OF A LINE FROM THE MEXICAN GULF OF MEXICO COAST 
NEAR 25N TO THE SOUTH OF BAJA CALIFORNIA NEAR 23N110W TO THE 
ITCZ NEAR 125W A LARGE TROUGH/CYCLONIC CIRCULATION IS OBSERVED. 
THIS AREA IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS 
INDICATING MODERATE TO STRONG MIDDLE AND UPPER LEVEL SUBSIDENCE 
IN THIS REGION. THIS FEATURE IS ALSO FORECAST TO RETREAT 
NORTHWARD THROUGH THE NEXT SEVERAL DAYS AND WEAKEN SLIGHTLY IN 
STRENGTH.

THE REMAINDER OF THE AREA WEST OF 90W...THAT IS...THE AREA 
SOUTHEAST OF THE TROUGH IS A BROAD SCALE ANTICYCLONIC 
CIRCULATION THAT IS MOIST IN THE MIDDLE AND UPPER LEVELS WITH 
AREAS OF MULTI LEVEL CLOUDINESS AND EMBEDDED AREAS OF 
CONVECTION. THIS FEATURE IS FORECAST TO PERSIST THROUGH THE NEXT 
SEVERAL DAYS WHILE EXPANDING TO COVER SOME OF THE AREA COVERED 
BY THE TROUGH AND ALSO WEAKENING SOME.

TROUGH IS EAST OF 90W WITH AN AXIS ALONG 83W. THIS REGION IS 
MOIST WITH AREAS OF MULTI LEVEL CLOUDS AND AREAS OF CONVECTION. 
THIS FEATURE IS FORECAST TO DRIFT EAST DURING THE NEXT SEVERAL 
DAYS.

WEAK SURFACE RIDGE IS NORTH OF A LINE FROM THE SOUTH TIP OF 
BAJA CALIFORNIA TO 15N120W TO 12N140W. THIS FEATURE IS FORECAST 
TO CHANGE LITTLE THROUGH THE NEXT SEVERAL DAYS. WEAK TROUGH 
WITHIN THE ITCZ NEAR 115W AND IS NEARLY STATIONARY. A WEAK LOW 
IS FORECAST TO DEVELOP WITHIN THIS TROUGH DURING THE NEXT 
SEVERAL DAYS. OTHERWISE A BROAD TROUGH IS ANALYZED AT THE 
SURFACE.

GAP WINDS...A BROAD TROUGH IS FORECAST OVER THE WESTERN 
CARIBBEAN AND THE EASTERN GULF OF MEXICO COUPLED WITH A RIDGE 
BUILDING OVER MEXICO SETTING UP THE CONDITIONS FOR N WINDS AT 20 
KT TO BRIDGE THE ISTHMUS OF TEHUANTEPEC INTO THE GULF OF 
TEHUANTEPEC TONIGHT AND INCREASING TO 20 TO 30 KNOTS BY MONDAY 
NIGHT.

$$
LL