000
AXPZ20 KNHC 250925
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT AUG 25 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

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

THE MONSOON TROUGH AXIS EXTENDS FROM THE EXTREME NW TIP OF 
COLOMBIA AT 11N75W WESTWARD ALONG 10N TO 10N81W...THEN TURNS NW 
GOING INLAND ACROSS CENTRAL NICARAGUA AND CENTRAL HONDURAS... 
THEN WESTWARD ACROSS CENTRAL GUATEMALA TO THE PACIFIC COAST AT 
14N92W. THE TROUGH AXIS THEN DIPS SW TO AN EMBEDDED SURFACE LOW 
PRESSURE 1009 MB AT 11.5N95W...WITH THE MONSOON TROUGH 
CONTINUING W BETWEEN 10N AND 12N TO BEYOND 140W.
 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED OFFSHORE 
THE COLOMBIAN COAST TO THE N OF 03N AND E OF 80W...AND ALSO 
WITHIN 75 NM OF THE PACIFIC COAST OF CENTRAL AMERICA FROM 80W TO 
94W...AND FROM 102W TO 106W. SIMILAR CONVECTION IS OBSERVED 
WITHIN 180 NM EITHER SIDE OF A LINE FROM 12N96W TO 07N106W...AND 
FROM 06N TO 12N BETWEEN 115W AND 126W...AND FROM 10N TO 12N 
BETWEEN 126W AND 136W.

...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE IS CENTERED JUST W OF THE AREA AT 
23N142W WITH A RIDGE EXTENDING NE TO ANOTHER ANTICYCLONE AT 
28N118W...WITH AN UPPER RIDGE CONTINUING E ACROSS THE NORTHERN 
BAJA CALIFORNIA PENINSULA TO A CREST OVER NORTHEASTERN OLD 
MEXICO AT 24N99W. VERY DRY UPPER AIR IS ADVECTED NE ALONG THE NW 
AND N PERIPHERIES OF THE UPPER RIDGE...TURNING E AND SE ACROSS 
CALIFORNIA AND ARIZONA. CONVECTION WAS ENHANCED ON FRI AFTERNOON 
S OF THE UPPER RIDGE ALONG...AND JUST INLAND THE PACIFIC COAST 
OF MEXICO...WITH THE RESULTANT UPPER DEBRIS MOISTURE SPREADING W 
OVER THE SOUTHERN GULF OF CALIFORNIA AND THE BAJA CALIFORNIA 
PENINSULA...AND OVER THE PACIFIC WATERS FROM 15N TO 23N BETWEEN 
THE WESTERN MEXICAN COAST AND 111W. A SMALL CLUSTER OF 
THUNDERSTORMS...CONFIRMED BY LIGHTNING DATA...IS CURRENTLY 
OBSERVED WITHIN 30 NM OF 22.5N110.5W.    
    
AN UPPER CYCLONE IS OVER THE DEEP TROPICAL PACIFIC AT 15N136W 
AND IS ALSO ACCOMPANIED BY DRY UPPER AIR NOTED WITHIN 240 NM OF 
CENTER. ANOTHER UPPER CYCLONE IS CENTERED NEAR 15N123W WITH DRY 
AIR INDICATED WITHIN 240 NM OVER ITS N SEMICIRCLE. THESE UPPER 
FEATURES COMBINE TO DRY OUT THE UPPER LEVELS GENERALLY TO THE N 
OF 15N W OF 113W.

AN UPPER TROUGH EXTENDS S ALONG THE EASTERN SEABOARD OF THE 
CONUS...ACROSS THE EASTERN GULF OF MEXICO AND THE WESTERN 
CARIBBEAN TO A BASE OVER THE PACIFIC COAST OF EL SALVADOR WITH 
CONVECTION ENHANCED ALONG THE BASE OF THIS UPPER TROUGH. STRONG 
NORTHEASTERLY UPPER FLOW IS OBSERVED OVER THE ENTIRE DEEP 
TROPICAL PORTION OF THE DISCUSSION AREA...BASICALLY TO S OF 
10N...AND IS ADVECTING DEBRIS MOISTURE...ASSOCIATED WITH 
CONVECTION ALONG THE MONSOON TROUGH...SOUTHWEST TO ALONG ABOUT 
04N WHERE IT EVAPORATES IN A BELT OF DRY UPPER AIR THAT EXTENDS 
FROM 20S NORTHWARD ACROSS THE EQUATOR TO ALONG 04N.        

ELSEWHERE AT THE LOW LEVELS...WEAK 1011 MB SURFACE LOWS ARE 
OBSERVED AT 20N112W AND 15.5N114.5W...BUT BOTH LACK SIGNIFICANT 
CONVECTION. A BROAD RIDGE DOMINATES THE SUBTROPICS W OF 120W 
WITH SURFACE WINDS GENERALLY 20 KT OR LESS. LONG PERIOD CROSS 
EQUATORIAL SOUTHERLY SWELLS ARE OBSERVED IN THE WATERS S OF 
01N BETWEEN 96W AND 103W RESULTING IN COMBINED SEAS TO 8 FT. 
THESE SWELL SHOULD REACH ALONG 03N BETWEEN 92W AND 113W TONIGHT 
WITH THE SOUTHERLY FLOW INCREASING TO 20 TO 25 KT...SEAS TO 8 
FT...IN THE WATERS FROM 08N TO 10N BETWEEN 108W AND 116W ON SUN 
NIGHT.    

$$
NELSON