000
AXPZ20 KNHC 260347
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN AUG 26 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0345 UTC.

...SPECIAL FEATURE...

A SURFACE LOW PRESSURE IS ANALYZED ALONG THE MONSOON TROUGH AXIS 
NEAR 11.5N 99.7W WITH AN ESTIMATED PRESSURE OF 1007 MB...AND IS 
MOVING W AT 07 KT. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
IS BECOMING ORGANIZED IN A BAND WITHIN 180 NM OVER THE NW 
QUADRANT. CONTINUED DEVELOPMENT IS POSSIBLE DURING THE NEXT 
COUPLE OF DAYS AND TROPICAL CYCLONE FORMATION IS POSSIBLE.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM THE EXTREME NW TIP OF 
COLOMBIA AT 09N78W WESTWARD ALONG 09N TO THE PANAMA/COSTA RICA 
BORDER...THEN TURNS NW ALONG THE PACIFIC COAST OF NICARAGUA...EL 
SALVADOR AND GUATEMALA...THEN TURNS SW ACROSS THE PACIFIC INTO 
THE EMBEDDED LOW PRESSURE AT 11.5N100W. THE MONSOON TROUGH AXIS 
THEN MEANDERS W BETWEEN 10N AND 13N TO BEYOND 140W.
 
ISOLATED MODERATE TO STRONG CONVECTION IS NOTED WITHIN 75 NM 
EITHER SIDE OF A LINE FROM 09N84W TO 09N94W. EXCEPT AS MENTIONED 
IN THE SPECIAL FEATURE...SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS NOTED FROM 07N TO 14.5N BETWEEN 100N AND 109W.
SIMILAR CONVECTION IS OBSERVED WITHIN 90 NM EITHER SIDE OF A 
LINE FROM 10N116W TO 10N133W.

...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE HAS SHIFTED SW OVER THE PAST 24 HOURS 
TO A POSITION W OF THE AREA AT 21N146W...BUT STILL RIDGES NE 
INTO THE AREA CRESTING AT 29N132W. A SECOND UPPER ANTICYCLONE IS 
OVER THE NORTHERN BAJA CALIFORNIA PENINSULA WITH A RIDGE SW TO A 
SHARP CREST AT 26N123W...AND A RIDGE ALSO EXTENDS SE TO A CREST 
OVER THE MEXICAN COAST AT 19N105W. CONVECTION HAS BEEN ENHANCED 
UNDER THIS RIDGE..ALONG AND JUST INLAND THE MEXICAN COAST FROM 
20N TO 27N. MOST OF THE DEBRIS MOISTURE IS ADVECTED 
ANTICYCLONICALLY S AND SW OVER THE PACIFIC FROM 16N TO 26N 
BETWEEN 104W AND 112W. 

AN UPPER CYCLONE NEAR 48N134W HAS DRAGGED AN UPPER TROUGH SE 
INTO THE DISCUSSION AREA ALONG 32N123W TO 25N126W AND INTO A 
WELL DEFINED UPPER CYCLONE AT 17N126W WHICH APPEARS TO BE 
SHIFTING W WITH TIME. THIS UPPER TROUGH HAS SPLIT THE 
ANTICYCLONIC FLOW ALOFT THAT HAS DOMINATED THE AREA THE PAST 
COUPLE OF DAYS. A SECOND UPPER CYCLONE IS OVER THE DEEP TROPICS 
AT 15N137W AND IS ALSO MOVING WESTWARD AND APPEARS TO BE 
FILLING. EXCEPT FOR THE DEBRIS MOISTURE PREVIOUSLY MENTIONED TO 
THE E OF 112W THE UPPER LEVELS ARE VERY DRY N OF 14N W OF 110W.

AN UPPER TROUGH EXTENDS S ALONG THE EASTERN SEABOARD OF THE 
CONUS...THEN DISSECTS THE GULF OF MEXICO THROUGH AN UPPER 
CYCLONE AT 23N87W TO ANOTHER UPPER CYCLONE OVER CENTRAL MEXICO 
AT 20N100W...WITH EVIDENCE OF THE UPPER TROUGH CONTINUING S TO 
YET ANOTHER UPPER CYCLONE AT 06N100W. SIGNIFICANT CONVECTION IS 
ENHANCED OVER LAND AROUND THE CYCLONE AT 20N100W WITH SOME OF 
THE CONVECTION SPREADING TO COAST NEAR 101W.

THE UPPER LEVELS OF THE TROPICS TO E OF 100W IS SLIGHTLY COMPLEX 
WITH AN UPPER CYCLONE OVER THE SW CARIBBEAN AT 14N79W AND 
ANOTHER OVER THE PACIFIC AT 04N94W. A SMALL UPPER ANTICYCLONE IS 
NOTED BETWEEN THE CYCLONES AT 12N83W. THE STRONG NORTHEASTERLY 
UPPER FLOW OBSERVED OVER THE ENTIRE AREA S OF 10N SEEMS TO HAVE 
BEEN SLIGHTLY DISRUPTED AND HAS WEAKENED SOME OVER THE PAST 24 
HOURS...BUT CONTINUES TO ADVECT MONSOON TROUGH DEBRIS MOISTURE 
SOUTHWEST TO ALONG ABOUT 04N. THE MOISTURE CONTINUES TO 
EVAPORATE IN A BELT OF DRY UPPER AIR THAT EXTENDS FROM 20S 
NORTHWARD ACROSS THE EQUATOR TO ALONG 04N.    

ELSEWHERE AT THE LOW LEVELS...A WEAK 1011 MB SURFACE LOW IS 
ANALYZED NEAR 15N114W WITH ONLY A COUPLE OF TSTMS OBSERVED 
18N114W. A BROAD RIDGE DOMINATES THE SUBTROPICS ELSEWHERE W OF 
120W WITH SURFACE WINDS GENERALLY 20 KT OR LESS. SOUTHWESTERLY 
MONSOON FLOW AT 20 TO 25 KT IS NOTED IN SCATTEROMETER DATA IN 
THE AREA FROM 03N TO 09N BETWEEN 100W AND 110W...WITH SEAS TO 8 
FT IN LONG PERIOD CROSS EQUATORIAL SWELLS THAT ARE CURRENTLY 
OBSERVED IN THE WATERS S OF 04N BETWEEN 92W AND 111W. THESE 
SWELLS ARE EXPECTED TO PROPAGATE N TO ALONG 11N BETWEEN 95W AND 
120W ON MON.

$$
NELSON