000
AXPZ20 KNHC 210941
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL 
1005 UTC SAT SEP 21 2013

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 
0930 UTC.

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

THE MONSOON TROUGH AXIS EXTENDS FROM 16N99W TO 12N110W TO 
12N120W TO 12N130W TO 10N140W. NO SIGNIFICANT CONVECTION IS 
NOTED.

...DISCUSSION...

W OF 110W...                                             
SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG 
SUBSIDENCE OVER JUST ABOUT THIS PORTION OF THE DISCUSSION AREA  
AS A LARGE ANTICYCLONE NEAR 24N117W CONTINUES TO BE THE MAIN 
FEATURE THAT DOMINATES HERE. THE RESULTANT DRY AND STABLE 
CONDITIONS ARE EVEN LIMITING CONVECTION FROM DEVELOPING IN THE 
TROPICAL REGION. ONLY WIDELY SCATTERED SHOWERS AND ISOLATED 
TSTMS ARE NOTED ALONG...AND WITHIN ABOUT 45 NM OF THE MONSOON 
TROUGH W OF 120W. PATCHES OF BROKEN STRATOCUMLUS CLOUDS ARE N OF 
18N BETWEEN 114W-125W. ONLY ISOLATED SHOWERS ARE NOTED ELSEWHERE 
S OF 16N.

A RATHER STRONG EARLY SEASON DEEP LAYER TROUGH IS JUST N OF THE 
AREA EXTENDING SW ACROSS THE FAR NW CORNER OF THE AREA. AN 
ASSOCIATED SURFACE COLD FRONT IS ANALYZED FROM 32N137W SW TO 
28N133W WHERE IT BECOMES FRAGMENTED TO 27N140W. ONLY ISOLATED 
SHOWERS ARE WITHIN 30 NM OF THE FRONT. ELSEWHERE ACROSS THE 
SURFACE...GENERALLY A WEAK PRES PATTERN REMAINS. THE DEEP LAYER 
TROUGH WILL CONTINUE TO SHIFT EASTWARD AND SHARPEN AS MOVES 
INLAND THE WESTERN U.S. THIS AFTERNOON AND EVENING. THE TROUGH 
WILL LEAVE BEHIND A CUT-OFF LOW NEAR 25N146W THROUGH MON. THE    
WEAKENING COLD FRONT WILL REACH FROM NEAR 32N122W TO 27N130W TO 
26N140W EARLY THIS EVENING...AND BARELY KEEPING ITS IDENTITY AS 
IT REACHES FROM NEAR THE SOUTHERN CALIFORNIA/NORTHERN BAJA 
PENINSULA BORDER SW TO NEAR 24N124W BY EARLY SUN EVENING. HIGH 
PRES RIDGING IN THE WAKE OF THE FRONT WILL BUILD EASTWARD 
THROUGH SUN LEADING TO A TIGHTENING OF THE PRES GRADIENT JUST TO 
THE N OF THE NE PART OF THE AREA. NLY WINDS THERE ARE FORECAST 
TO INCREASE TONIGHT AND SUN. THIS INCREASE IN WINDS WILL SEND 
SEAS BUILDING TO S OF 32N IN THE FAR NE PORTION. ON MON THE HIGH 
PRES RIDGE WEAKENS AS ANOTHER COLD FRONT MOVES SEWD JUST NW AND 
N OF THE AREA.

E OF 110W...                                                 
DEEP ATMOSPHERIC MOISTURE IS EVIDENT OVER THIS PORTION OF THE 
AREA AS THE CIRCULATION AROUND AN ANTICYCLONE CENTERED OVER 
EASTERN MEXICO NEAR 24N99W DRIVES MOISTURE DERIVED FROM 
CONVECTION OVER SOUTHERN MEXICO...AND WITH THAT TIED TO THE 
MONSOON TROUGH SEGMENT ACROSS PARTS OF CENTRAL AMERICA WESTWARD 
TO 110W. A MID TO UPPER LEVEL INVERTED TROUGH IN THE EASTERLY 
FLOW S OF THE ANTICYCLONE HAS MOVED W TO ALONG 110W N OF 08N. 
THE TROUGH IN COMBINATION WITH VERY MOIST SURFACE FLOW 
THROUGHOUT IS HELPING TO SET OFF ISOLATED SHOWERS AND TSTMS N OF 
08N BETWEEN 101W AND 110W. CLUSTERS OF SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION ARE NOTED ALONG...AND WITHIN 
45 NM OF THE COASTS OF MEXICO AND CENTRAL AMERICA. SIMILAR 
CONVECTION IS WITHIN 45 NM OF 08N91W...AND 30 NM OF 07N88W. THE 
OVERALL COVERAGE OF CONVECTION IN THE TROPICS REMAINS QUITE 
MINIMAL GIVEN THE TIME OF YEAR. THE MID/UPPER LEVEL TROUGH WILL 
MOVE W OF 110W IN A FEW HOURS. NO SIGNIFICANT INCREASE IN 
CONVECTION IS EXPECTED THROUGH MON...WITH LITTLE CHANGES IN 
CURRENT OBSERVED MARINE CONDITIONS ALSO EXPECTED.
 
$$
AGUIRRE