000
AXPZ20 KNHC 170913
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT SEP 17 2011

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 
0845 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS W FROM THE N COAST OF COSTA RICA 
AT 09N84W TO 14N95W...THEN DISCONTINUOUS STARTING AGAIN AT 
18N108W TO 14N110W TO LOW PRES NEAR 12N132W 1012 MB TO 10N140W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION BETWEEN THE 
TROUGH AXIS AND THE CENTRAL AMERICAN COAST FROM 09N TO 14N. 
SCATTERED MODERATE CONVECTION WITHIN 120 NM S OF AXIS BETWEEN 
112W AND 116W. 

...DISCUSSION... 

A MID TO UPPER LEVEL TROUGH EXTENDING FROM THE NORTHERN ROCKIES 
TO NEAR 28N130W IS BECOMING MORE DEAMPLIFIED AHEAD OF A DEEP 
LAYER RIDGING ALONG 155W SHIFTING SLOWLY E. THE ASSOCIATED 
SURFACE RIDGING W OF 120W IS SUPPORTING AREAS OF PERSISTENT 20 
KT TRADE WINDS BETWEEN THE MONSOON TROUGH AND 20N W OF 125W AS 
NOTED ON A 0240 UTC WINDSAT PASS. 20 KT SW WINDS ARE ALSO NOTED 
FROM 06N TO THE MONSOON TROUGH...S OF A WEAK LOW PRES AREA ALONG 
THE TROUGH NEAR 12N132W. DESPITE BETTER LOW LEVEL 
CONVERGENCE...CONVECTION ALONG THE MONSOON TROUGH HAS DIMINISHED 
IN THIS AREA MAINLY DUE TO DECREASING DEEP LAYER MOISTURE.

FURTHER E...A BROAD UPPER ANTICYCLONE IS CENTERED OVER CENTRAL 
MEXICO...SE OF THE WEEK MID TO UPPER LEVEL TROUGH. DEEP LAYER 
SOUTHERLY FLOW ON THE SW SIDE OF THE UPPER ANTICYCLONE HAS 
PUSHED THE MONSOON TROUGH NORTHWARD TO JUST OFF MANZANILLO 
MEXICO. IN FACT ASCAT DATA FROM 04 UTC SHOW SE FLOW ASSOCIATED 
WITH AN ELONGATED CLOSED CIRCULATION ALONG THE MONSOON TROUGH 
NEAR 110W...HINTING THAT THE TROUGH MAY BREAK AS WEAK LOW PRES 
FORMS. IT IS NOT CLEAR AT THIS TIME THAT A DISTINCT LOW PRES 
AREA HAS FORMED AS YET WITH NO VISIBLE IMAGERY AVAILABLE...BUT 
CONSENSUS AMONG GLOBAL MODELS CONTINUES TO SHOW LOW PRES 
DEEPENING TO AT LEAST 1008 MB NEAR 15N112W BY 48 HOURS. ASCAT 
DATA SHOW SW WINDS TO 20 KT CONVERGING INTO THE ELONGATED CLOSED 
CIRCULATION ALONG THE TROUGH...SUPPORTING CONVECTION S OF THE 
TROUGH AXIS BETWEEN 112W AND 116W.

ANOTHER PERTURBATION IS FORMING ALONG THE MONSOON TROUGH FURTHER 
TO SE NEAR 10N90W. NO DISCERNIBLE CLOSED CIRCULATION IS 
NOTED...BUT AGAIN THE CONSENSUS OF GLOBAL MODELS INDICATES A LOW 
MAY FORM IN THIS AREA OVER THE NEXT 48 HOURS...ESPECIALLY AS A 
WEAK TROUGH IN THE WESTERN CARIBBEAN MIGRATES W. NORTHERLY GAP 
WINDS THROUGH THE GULF OF TEHUANTEPEC WILL INCREASE LATER THIS 
MORNING AS THE TROUGH APPROACHES FROM THE E...TAPPING SLIGHTLY 
DRIER AND DENSER AIR OVER THE WESTERN GULF OF MEXICO. THIS 
ENHANCED GAP FLOW WILL PERSIST THROUGH SUN PROVIDED THE LOW 
FORMS TO THE SOUTH AS EXPECTED...WITH DIURNAL MAXIMUMS IN THE 
EARLY MORNING HOURS. SEAS WILL BUILD TO 9 FT BY EARLY SUN.
  
$$
CHRISTENSEN