000
AXPZ20 KNHC 220928
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT AUG 22 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 
0900 UTC.

...SPECIAL FEATURE....
AN AREA OF LOW PRESSURE CENTERED NEAR 14N135W 1008 MB IS MOVING 
W NEAR 10 KT. WHILE AN ASSOCIATED AREA OF DEEP CONVECTION HAS 
BEEN PERSISTING OVERNIGHT...MICROWAVE DATA INDICATES THAT THIS 
CONVECTIVE MASS IS DISPLACED WELL TO THE W OF THE LOW-LEVEL 
CENTER. THIS DECOUPLED STRUCTURE IS DUE TO MODERATE TO STRONG 
ELY SHEAR. A QUIKSCAT PASS AROUND 03Z REVEALED 20-30 KT WINDS 
WITHIN 300 NM N AND 90 NM S SEMICIRCLES. THIS SYSTEM IS BEING 
CLOSELY MONITORED AND COULD BECOME A TROPICAL CYCLONE IF THE 
CONVECTIVE STRUCTURE IMPROVES.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 105W FROM 08N TO 17N MOVING W 15 KT. 
SHORTWAVE IR SATELLITE IMAGES SHOW AN IMPROVED AREA OF LOW TO 
MID-LEVEL CYCLONIC TURNING WITH EVIDENCE OF A CIRCULATION CENTER 
ALONG THE AXIS NEAR 12N. CONVECTION HAS ALSO INCREASED 
ESPECIALLY IN A BROAD BAND S OF THE CENTER WITHIN THE ITCZ FROM 
09N TO 12N BETWEEN 105W AND 115W. A 0458 Z ASCAT PASS REVEALS 
PRONOUNCED LOW-LEVEL CONVERGENCE S OF CENTER...TRIGGERING THE 
AFOREMENTIONED CONVECTION...AND LIGHT AND VARIABLE FLOW NEAR THE 
CENTER. SOME SLOW DEVELOPMENT IS POSSIBLE OVER THE NEXT COUPLE 
OF DAYS.

TROPICAL WAVE IS ALONG 120W FROM 07N TO 18N MOVING W 10 KT. THIS 
WAVE IS NOT AS WELL-DEFINED AS THE ONE ALONG 105W. SOME CYCLONIC 
TURNING IS APPARENT...BUT CONVECTION IS MINIMAL.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 09N84W 12N102W 11N115W 13N134W 
12N140W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 10N TO 
13N BETWEEN 97W AND 100W. SCATTERED MODERATE TO STRONG 
CONVECTION IS FROM 09N TO 13N BETWEEN 108W AND 116W. 

...DISCUSSION...

N OF 20N...
A FAIRLY COMPLEX MID-UPPER PATTERN REMAINS IN PLACE ACROSS THE 
SUBTROPICS. AN UPPER HIGH IS OVER SRN MEXICO...AN UPPER LOW OFF 
THE NRN BAJA COAST...ANOTHER UPPER HIGH NEAR 23N133W...AND 
ANOTHER UPPER LOW NEAR 23N145W. WHILE THE PATTERN IS AMPLIFIED 
...THE ONLY SENSIBLE WEATHER IS NEAR MEXICO WHERE UPPER 
DIFFLUENCE AND LOW-LEVEL CONVERGENCE ASSOCIATED WITH LOCAL 
EFFECTS/DRAINAGE IS PRODUCING SCATTERED SHOWERS AND TSTMS FROM 
19N-28N BETWEEN 103W-109W. A WEAK SFC TROUGH...ASSOCIATED WITH 
THE UPPER LOW OFF THE NRN BAJA COAST...HAS WEAKENED THE TRADES. 
THIS TROUGH WILL PERSIST FOR THE NEXT COUPLE OF DAYS ALLOWING 
WINDS TO BE MAINLY LESS THAN 20 KT...EXCEPT FOR OVER THE FAR NW 
CORNER. A MIX OF N AND S SWELL WILL ELEVATE SEAS TO 6 TO 8 FT 
ACROSS MUCH OF THE AREA SUN AND MON.

S OF 20N...
ELY MID-UPPER FLOW AND A HIGHLY MOIST ENVIRONMENT IS PRESENT 
ACROSS THE TROPICS. CONVECTION IS FOCUSED AROUND THE TROPICAL 
WAVES AND THE ITCZ. SEE ABOVE FOR MORE DETAILS. LONG 
PERIOD...14-17 SECONDS... S TO SW SWELL IS PROPAGATING ACROSS 
MUCH OF THE AREA AND WILL CONTINUE FOR THE NEXT COUPLE OF DAYS. 
  
$$
CANGIALOSI