000
AXPZ20 KNHC 200957
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL 
1005 UTC FRI SEP 20 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 13N106W TO 
13N120W TO 12N131W...WHERE IT TRANSITIONS TO AN ITCZ TO 09N140W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 120 NM N 
OF TROUGH E OF 102W TO INLAND MEXICO.

...DISCUSSION...

W OF 110W...                                             
SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG 
SUBSIDENCE OVER JUST ABOUT THE ENTIRE AREA W OF 110W AS A LARGE 
ANTICYCLONE ANCHORED NEAR 24N120W IS THE MAIN FEATURE DOMINATING 
THAT PORTION OF THE AREA. THE RESULTANT DRY AND STABLE CONDITIONS 
ARE EVEN LIMITING CONVECTION FROM DEVELOPING IN THE TROPICAL 
REGION AS NO CONVECTION IS CURRENTLY OBSERVED THERE. PATCHES OF 
BROKEN STRATOCUMLUS CLOUDS ARE N OF 18N BETWEEN 112W-126W. ONLY 
ISOLATED SHOWERS ARE NOTED S OF 15N.

A 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 TO ALONG 30N W OF 140W WHERE IT BEGINS 
TO WEAKEN. GENERALLY A WEAK PRES PATTERN EXISTS ACROSS THE AREA. 
THE TROUGH IS FORECAST TO SHIFT EASTWARD AND DEEPEN AS MOVES 
INLAND THE WESTERN U.S. SAT. THE COLD FRONT WILL REACH FROM NEAR 
32N129W TO 27N140W EARLY THIS EVENING...THEN FROM SOUTHERN 
CALIFORNIA TO 29N128W...AND DISSIPATING STATIONARY TO 27N140W BY 
SAT EVENING BEFORE IT DISSIPATES. HIGH PRES RIDGING IN THE WAKE 
OF THE FRONT WILL BUILD EASTWARD THROUGH SUN LEADING TO A 
TIGHTENING OF THE PRES GRADIENT JUST N OF THE NE PART OF THE 
AREA. NLY WINDS THERE ARE FORECAST TO INCREASE WITH RESULTANT 
SEAS EXPECTED TO BUILD TO 8 FT SUN IN THE FAR NE PORTION AS NLY 
SWELLS GENERATED FROM THE INCREASING NLY FLOW N OF THE AREA SEEP 
TO S OF 30N. 

E OF 110W...                                                 
DEEP ATMOSPHERIC MOISTURE IS EVIDENT OVER THIS PORTION OF THE 
AREA AS THE CIRCULATION AROUND AN ANTICYCLONE CENTERED OVER 
CENTRAL MEXICO NEAR 24N102.5W DRIVES MOISTURE DERIVED FROM 
CONVECTION OVER SOUTHERN MEXICO...AND WITH THAT TIED TO THE 
MONSOON TROUGH SEGMENT ACROSS CENTRAL AMERICA WESTWARD TO 110W. 
A MID TO UPPER LEVEL INVERTED TROUGH IN THE EASTERLY FLOW S OF 
THE ANTICYCLONE IS ALONG 105W N OF 09N. THE TROUGH IN 
COMBINATION WITH VERY MOIST SURFACE FLOW THROUGHOUT IS HELPING 
TO SET OFF WIDELY SCATTERED SHOWERS AND TSTMS N OF 09N E OF 
103W. CLUSTERS OF SCATTERED STRONG CONVECTION ARE NOTED 
ALONG...AND WITHIN 60 NM OF THE COASTS OF MEXICO AND CENTRAL 
AMERICA. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED 
WITHIN 45 NM OF 08N93W...AND WITHIN 45 NM OF LINE FROM 08N87W TO 
06N87W. DESPITE THE OBSERVANCE OF THE AFOREMENTIONED 
CONVECTION...THE ACTIVITY IS MARKEDLY LESS IN COVERAGE THAN WHAT 
OCCURRED RECENTLY IN THE VERY ACTIVE MONSOON TROUGH THAT 
EVENTUALLY HELPED SPAWN RECENT TROPICAL CYCLONE MANUEL. THE 
MID/UPPER LEVEL TROUGH WILL MOVE W OF 110W EARLY SAT. NO 
SIGNIFICANT INCREASE IN CONVECTION IS EXPECTED THROUGH 
SUN...WITH LITTLE CHANGE IN MARINE CONDITIONS.
 
$$
AGUIRRE