000
AXPZ20 KNHC 300254
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU JUL 30 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0245 UTC.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 88W/89W N OF 04N MOVING W 20-22 KT OVER THE 
PAST 24 HOURS. CONVECTION IS LIMITED ALONG THE IMMEDIATE WAVE 
AXIS OVER THE PACIFIC BUT WAS ACTIVE NEAR THE N END OF THE WAVE 
OVER EL SALVADOR AND GUATEMALA. ADDITIONAL SCATTERED MODERATE TO 
STRONG CONVECTION WAS OCCURRING OVER PANAMA AND COSTA RICA BUT 
NOT ASSOCIATED WITH THE WAVE. 

TROPICAL WAVE FROM 09N TO 17N ALONG 116W MOVING W AN AVERAGE OF 
10 KT OVER THE PAST 24 HOURS. SATELLITE IMAGES INDICATED A LESS 
DISTINCT AREA OF MID LEVEL CYCLONIC TURNING WITHIN THE 
CONVECTION AS THE WAVE IS INTERACTING WITH AN UPPER LEVEL LOW
NEAR 16N121W. SCATTERED MODERATE CONVECTION IS CONFINED TO 
WITHIN 90-120 NM EITHER SIDE OF THE WAVE AXIS. DEVELOPMENT IS 
NOT EXPECTED AS LONG AS THE WAVE MOVES IN TANDEM WITH THE UPPER 
LOW. 

AN AREA OF LOW PRESSURE HAS DEVELOPED NEAR 12N IN ASSOCIATION 
WITH THE TROPICAL WAVE CURRENTLY ALONG 135W. THE WAVE AND LOW 
ARE MOVING W NEAR 12 KT. CONVECTION APPEARS SOMEWHAT ORGANIZED 
WITH WELL DEFINED MID LEVEL TURNING NOTED NEAR 12N136W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 180 NM W 
AND 90 NM E SEMICIRCLE OF THE LOW. A 1910 UTC ASCAT PASS 
INDICATED A CLOSED BUT ELONGATED CIRCULATION. THE WAVE AND LOW 
ARE ALSO SITUATED IN AN AREA OF INCREASING ANTICYCLONIC FLOW 
ALOFT WHICH APPEARS TO BE A FAVORABLE ENVIRONMENT FOR 
DEVELOPMENT. 

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...08N78W TO 
09N90W TO 07N100W TO 13N115W TO 10N140W. SCATTERED MODERATE TO 
STRONG WITHIN 90 NM OF THE AXIS E OF 87W TO THE COAST OF COSTA 
RICA AND PANAMA.  SCATTERED MODERATE ISOLATED STRONG ELSEWHERE 
WITHIN 180 NM S OF THE AXIS E OF 88W...WITHIN 90-120 NM OF THE 
AXIS BETWEEN 93W AND 97W. SCATTERED MODERATE WITHIN 120 NM OF 
THE AXIS BETWEEN 105W AND 118W. 

...DISCUSSION...

A HIGHLY DIFFLUENT UPPER PATTERN OVER THE DEEP TROPICS IS 
ENHANCING CONVECTION NEAR THE TROPICAL WAVE AND LOW PRESSURE 
ALONG 135W AND OVER THE ITCZ WEST OF 125W. AS NOTED ABOVE A HIGH 
RESOLUTION ASCAT PASS AT 1910 UTC INDICATED A SURFACE LOW HAS 
FORMED. IN ADDITION THIS PASS INDICATED NE-E WINDS OF 20 TO 
LOCALLY 25 KT IN THE VICINITY OF THE WAVE IN RESPONSE TO THE 
STEEPENED PRESSURE GRADIENT BETWEEN IT AND THE SUBTROPICAL 
RIDGE. THE HIGHER WINDS ARE REFLECTED IN THE HIGH SEAS FORECAST. 
THIS WAVE IS EXPECTED TO CONTINUE W AT 10-15 KT WITH THE 20-25 
KT FLOW GRADUALLY SHIFTING W WITH IT. 

DIFFLUENT UPPER FLOW OVER NORTHERN MEXICO HAS PRODUCED 
WIDESPREAD MULTI LEVEL BROKEN TO OVERCAST CLOUDINESS AND ONCE 
AGAIN CLUSTERS OF STRONG CONVECTION FROM 21N TO THE U.S. BORDER 
GENERALLY ALONG THE SIERRA MADRE OCCIDENTAL. BESIDES THE 
TROPICAL WAVES AND ITCZ RELATED CONVECTION...MUCH OF THE 
REMAINDER OF THE BASIN IS EXPERIENCING FAIR WEATHER. 

MODERATING TRADES ACROSS THE CARIBBEAN ARE RESULTING IN WEAKENED 
FLOW THROUGH THE GULF OF PAPAGAYO. A 1518 UTC ASCAT PASS 
REVEALED WINDS OF 15-20 KT IN THE GAP. NWP MODELS AGREE IN 
DIMINISHING WINDS BELOW 20 KT WITHIN THE NEXT 36 HOURS.

$$
COBB