000
AXPZ20 KNHC 202145
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON SEP 20 2010

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...
A MONSOON TROUGH NOT DESCRIBED BY AN ITCZ EXTENDS FROM 19N110W 
TO LOW PRES 13N124W 1008 MB TO 11N140W. SCATTERED MODERATE 
CONVECTION WITHIN 90 NM S OF TROUGH W OF 128W.

...DISCUSSION...

ALOFT...
RIDGE EXTENDS WSW FROM 30N110W THROUGH AN ANTICYCLONE CENTERED 
NEAR 25N123W TO BEYOND 20N140W. THE RIDGE WILL REMAIN NEARLY 
STATIONARY THE NEXT 12-24 HOURS THEN SHIFT ESE TUE THROUGH WED 
AS A SHORT WAVE TROUGH APPROACHES THE W COAST OF THE U.S. AN 
ANTICYCLONE CENTERED SW OF BROWNSVILLE TX DOMINATES THE GULF OF 
MEXICO AND MOST OF MEXICO. FAVORABLE DIVERGENT UPPER WINDS SW OF 
THIS HIGH IS ENHANCING NOCTURNAL CONVECTION MOVING W OFF THE 
SLOPES OF THE SIERRA MADRE INTO MEXICAN COASTAL WATERS. LIGHT TO 
MODERATE EASTERLY WINDS ACROSS THE AREA S OF THE RIDGE IS 
ENHANCING DEEP CONVECTION SOUTH OF THE MONSOON TROUGH BETWEEN 
105W AND 138W...AND MODERATE TO STRONG CONVECTION N OF 10N 
BETWEEN 91W AND 195W FROM DIFFLUENT FLOW ALOFT. CONVECTION HAS 
RAPIDLY DISSIPATED TODAY NEAR A LOW AT 21N109W...REVEALING AN 
EXPOSED LL CIRCULATION. 

SURFACE...
THE EXPOSED LOW MENTIONED ABOVE IS MOVING INTO COOLER WATERS AND 
ITS PROSPECTS TO DEVELOP INTO A TROPICAL CYCLONE ARE LOWER. WEAK 
RIDGE EXTENDS SE FROM 1018 MB HIGH CENTERED NEAR 32N137W TO NEAR 
25N125W. PRESSURE GRADIENT BETWEEN RIDGE AND A STATIONARY THERMAL
TROUGH OVER GULF OF CALIFORNIA IS PRODUCING 20-25 KT NW WINDS N 
OF 24N E OF 121W TO W COAST OF BAJA CALIFORNIA WITH SEAS TO 9 
FT. WINDS AND SEAS ARE EXPECTED TO DIMINISH THERE IN ABOUT 24 
HOURS. THE MONSOON TROUGH AND ASSOCIATED FLOW MENTIONED ABOVE 
DOMINATES REST OF THE BASIN AND EXTENDS ENE INTO CENTRAL AMERICA 
AND THE FAR SW CARIBBEAN. GFS MODEL SHOWS A LOW IN THE MONSOON 
TROUGH NEAR 13N124W GAINING STRENGTH AND MOVING EAST TO NEAR 108W
THU. THIS TYPE OF MOTION IS VERY UNUSUAL IN THE E PACIFIC BASIN 
ESPECIALLY W OF 115W. BUT GFS MODEL HAS BEEN VERY CONSISTENT RUN-
TO-RUN IN LOCATION MOVEMENT AND INTENSIFICATION OF THE LOW...SO 
IT BEARS CLOSE SCRUTINY.

MARINE...
FRESH TO STRONG SW WINDS PERSIST UP TO 200 NM S OF THE MONSOON 
TROUGH AXIS...AND ARE PRODUCING 10 FT SEAS BETWEEN 101W AND 115W 
AND SEAS TO 9 FT BETWEEN 115W AND 129W. MODEL GUIDANCE SHOWS 
ISOLATED AREAS OF WINDS TO 30 KT IN ABOUT 48 HOURS IN THIS AREA.

$$
MUNDELL