000
AXPZ20 KNHC 201521
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED MAY 20 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...06N77W TO 
07N105W TO 10N120W TO 04N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN 75 NM OF THE POINT 07N78.5W. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN 75 NM EITHER SIDE OF THE 
LINE FROM 08.5N95W TO 13.5N102.5W TO 07N110W. SCATTERED MODERATE 
TO STRONG CONVECTION IS WITHIN 90 NM OF THE POINT 08.5N114W. 
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE LINE FROM 
11.5N119W TO 09N125W. SCATTERED MODERATE TO STRONG CONVECTION IS 
WITHIN 75 NM EITHER SIDE OF THE LINE FROM 08N127W TO 05N136W.

.DISCUSSION...

MIDDLE AND UPPER LEVEL SHORTWAVE IS OVER THE NORTHEAST PART OF 
THE PACIFIC OCEAN AREA NORTH OF 20N E OF 130W. ASSOCIATED 
SIGNIFICANT WEATHER IS OVER INTERIOR MAINLAND MEXICO IN THE FORM 
OF DEEP LAYER MOISTURE PRODUCED BY DIFFLUENT FLOW ALOFT WITH 
MULTI LEVEL CLOUDS AND EMBEDDED WIDELY SCATTERED CONVECTIVE 
ACTIVITY. THE TROUGH IS FORECAST TO CONTINUE TO MOVE SLOWLY EAST 
OVER THE SOUTHWEST UNITED STATES AND NORTHERN MEXICO THROUGH 
FRIDAY. ASSOCIATED WEATHER WILL CONTINUE TO BE OVER INTERIOR AND 
EASTERN MAINLAND MEXICO.

REMAINDER OF THE MIDDLE AND UPPER LEVELS IS BROAD ANTICYCLONIC 
FLOW. MOST OF THE AREA IS DRY AND CLOUD FREE IN THE MIDDLE AND 
UPPER LEVELS THE EXCEPTION IS AN AREA NORTH OF THE ITCZ AND 
SOUTH OF A LINE FROM THE ITCZ AT 140W TO 15N120W TO SOUTHERN 
MEXICO NEAR THE GULF OF TEHUANTEPEC. THIS AREA IS DIFFLUENT 
ALOFT WITH MULTI LEVEL CLOUDS AND WIDESPREAD AREAS OF EMBEDDED 
CONVECTION. MOST OF THIS ACTIVITY IS WEST OF 95W. TWO SURFACE 
LOWS ARE WITHIN THIS AREA. ONE CENTERED NEAR 11N109W 1007 MB AND 
IS STATIONARY. THIS LOW IS FORECAST TO REMAIN STATIONARY FOR THE 
NEXT SEVERAL DAYS AND SLOWLY DEVELOP. ANOTHER IS CENTERED NEAR 
12N120W 1007 MB AND IS ALSO STATIONARY. THIS LOW IS FORECAST TO 
REMAIN WEAK AND BECOME DIFFUSE FRIDAY.

WEAK SURFACE RIDGE IS NORTH OF 15N WEST OF 115W. BESIDES THE TWO 
LOWS MENTIONED ABOVE A BROAD TROUGH IS ANALYZED OVER THE AREA.

GAP WINDS HAVE CONTINUED IN THE GULF OF TEHUANTEPEC REGION. GALE 
CONDITIONS SHOULD END MIDDAY TODAY AND RAPIDLY DECREASE TO LESS 
THAN 20 KT MIDDAY THURSDAY.

$$
LL