000
AXPZ20 KNHC 282205
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE JUL 28 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...TROPICAL WAVES...

TROPICAL WAVE FROM 07N TO 16N ALONG 110W/111W MOVING W NEAR 15 
KT. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 09N TO 
15N WITHIN 240 NM W AND 90 NM E OF THE WAVE AXIS. MID LEVEL 
CYCLONIC TURNING WAS NOTED WITHIN THE CONVECTION AND WAS MOST 
PRONOUNCED IN VISIBLE SATELLITE IMAGERY. THE GFS COMPUTER MODEL 
MOVES THE SYSTEM WEST AND MAINTAINS A LARGE BUT WEAK LOW WITH 
THE WAVE FOR THE NEXT SEVERAL DAYS AND DOES NOT DEVELOP THE 
CIRCULATION. WEAK UPPER LEVEL OUTFLOW IS NOTED. SOUTHWESTERLY 
SHEAR IS SWEEPING OVER THE SYSTEM.

TROPICAL WAVE FROM 05N TO 16N ALONG 128W MOVING W NEAR 15 KT. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 09N TO 15N 
WITHIN 180 NM W AND 90 NM E OF THE WAVE AXIS. THE GFS COMPUTER 
MODEL MOVES THE SYSTEM W AND ONLY SLIGHTLY DEVELOPS THE 
CIRCULATION. THE WAVE IS EMBEDDED WITHIN AN AREA OF MODERATE 
UPPER LEVEL DIFFLUENCE. SOUTHERLY SHEAR IS BEGINNING TO IMPACT 
THE SYSTEM.

TROPICAL WAVE FROM 04N TO 12N ALONG 138W MOVING W 15-18 KT OVER 
THE PAST 24 HOURS. SCATTERED MODERATE CONVECTION IS FROM 05N TO 
10N W OF THE AXIS. THE SYSTEM IS SLATED TO MOVE WEST OF THE AREA 
WITHIN 12-18 HOURS. 

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...07N78W TO 
06N95W TO 12N110W TO 10N120W TO 12N127W TO 07N140W. SCATTERED 
MODERATE ISOLATED STRONG WITHIN 180-240 NM OF THE AXIS W OF 
110W. SCATTERED MODERATE FROM 12N TO 18N BETWEEN 102W AND 110W. 
SCATTERED  MODERATE WITHIN 90 NM S OF THE AXIS BETWEEN 82W AND 
95W. 

...DISCUSSION...

AN UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC CIRCULATION N OF 
THE DISCUSSION AREA NEAR 38N141W. THE TROUGH IS CONFINED TO THE 
NORTHWEST PORTION OF THE DISCUSSION AREA WEST OF A LINE THROUGH 
32N128W TO THE ITCZ NEAR 140W. AN ANTICYCLONIC CIRCULATION WAS 
CENTERED SE OF THE TROUGH NEAR 18N125W WITH ASSOCIATED UPPER 
DIFFLUENT FLOW EXTENDING OUT ABOUT 360 NM. DIFFLUENT FLOW WAS 
ENHANCING CONVECTION IN ASSOCIATION WITH THE THE TROPICAL WAVE 
ALONG 128W. 

ANOTHER LARGE UPPER ANTICYCLONIC CIRCULATION IS CENTERED OVER NW 
MEXICO NEAR 28N108W...DOMINATING THE FLOW OVER MOST OF MEXICO 
AND THE NE PACIFIC. UPPER LEVEL DIFFLUENT FLOW WITH MULTI LEVEL 
CLOUDS IS OVER MEXICO N OF 25N. A FAIRLY LARGE CYCLONIC 
CIRCULATION...ABOUT 360 NM IN DIAMETER...SITUATED BETWEEN THE 
TWO ANTICYCLONES NOTED ABOVE NEAR 18N115W IS MOVING WEST AT 15 
KT. THIS FEATURE WAS BEGINNING TO IMPINGE UPON THE ANTICYCLONE 
NEAR 18N125W. SOUTHWESTERLY FLOW ON THE E SIDE OF THIS 
CIRCULATION WAS PROVIDING SHEAR OVER THE TROPICAL WAVE ALONG 
110W/111W.
 
A FLAT UPPER LEVEL RIDGE COVERS THE TROPICAL PACIFIC S OF 15N 
BETWEEN 95W AND 110W. THIS AREA IS SLIGHTLY DIFFLUENT ALOFT WITH 
MOIST MIDDLE AND UPPER LEVELS AND ENHANCED CONVECTION WITHIN THE 
ITCZ W OF 100W. AN INVERTED UPPER LEVEL TROUGH IS OBSERVED WITH 
AN AXIS ALONG 87W.

AT THE SURFACE...MODERATE SURFACE RIDGE IS NORTH OF 16N WEST OF 
112W. NE TO E GAP WINDS OF 20 TO 25 KT CONTINUE IN AND 
DOWNSTREAM FROM THE GULF OF PAPAGAYO REGION. THESE WINDS ARE 
FORECAST TO DROP BELOW 20 KT WITHIN 48 HOURS. 

$$
COBB