000
AXPZ20 KNHC 192135
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 19 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...
MONSOONAL S TO SW FLOW NOT DESCRIBED BY THE ITCZ DOMINATES THE 
DEEP TROPICS ACROSS THE AREA...WITH A MONSOON TROUGH EXTENDING 
FROM LOW PRES 17N105W 1007 MB TO 13N110W TO LOW PRES 13N125W 
1008 MB TO 09N140W. SCATTERED MODERATE CONVECTION WITHIN 120 NM 
S OF TROUGH BETWEEN 107W AND 120W...AND WITHIN 90 NM S OF TROUGH 
BETWEEN 130W AND 137W.

...DISCUSSION...

ALOFT...
SW WINDS PREVAIL OVER NW PORTION OF AREA BETWEEN LONG WAVE TROUGH
ALONG 126W AT THE CAL/ORE COAST AND A SUBTROPICAL RIDGE EXTENDING
WSW FROM ANTICYCLONE NEAR 27N117W TO BEYOND 19N140W. TROUGH WILL 
WEAKEN AND MOVE NE LATER TONIGHT WHILE ANTICYCLONE AND RIDGE AXIS
REMAIN NEARLY STATIONARY. PROMINENT ANTICYCLONE IN WESTERN GULF 
OF MEXICO NEAR 25N96W. FAVORABLE DIVERGENT UPPER LEVEL FLOW SW 
OF THIS FEATURE IS ENHANCING DEEP CONVECTION ASSOCIATED WITH THE 
SURFACE MONSOON TROUGH E OF 112W. UPPER LEVEL WINDS REMAIN QUITE 
STRONG EXCEPT IN IMMEDIATE VICINITY OF THE MONSOON TROUGH...AND 
VERTICAL SHEAR IS PREVENTING MOST OF THE LOW PRESSURE AREAS FROM 
DEVELOPING INTO COHERENT LOWS WITH POTENTIAL TO BECOME TROPICAL 
CYCLONES. MODEL GUIDANCE SHOWS WINDS ALOFT DECREASING SOMEWHAT 
OVER THE NEXT COUPLE OF DAYS...WHICH COULD ALLOW A LOW CENTERED 
S OF MANZANILLO MEXICO NEAR 17N105W TO BECOME A TROPICAL CYCLONE.
THE CHANCE OF TC FORMATION IN THIS AREA RATED MEDIUM AT 40 PCT.

SURFACE...
TROUGH MENTIONED ABOVE SUPPORTING A WEAKENING COLD FRONT THAT 
EXTENDS FROM 32N126W TO 25N140W MOVING E AT 10 KT. THE FRONT 
WILL WEAKEN INTO FRONTAL TROUGH FROM 30N127W TO 26N140W TONIGHT 
THEN DISSIPATE MON. SCATTEROMETER AND ALTIMETRY DATA SHOWS WINDS 
LESS THAN 20 AND 7-8 FT SEAS ASSOCIATED WITH FRONT. WEAK RIDGING 
AHEAD OF THE FRONT COMBINED WITH LOW PRES OVER NW MEXICO AND 
BAJA CALIFORNIA CREATING 20-25 KT NW WINDS N OF 23N E OF 120W TO 
W COAST OF BAJA CALIFORNIA. LITTLE CHANGE EXPECTED NEXT 2 DAYS. 
MONSOON TROUGH MENTIONED ABOVE IN ITCZ SECTION DOMINATES REST OF 
THE BASIN. SCATTEROMETER DATA SHOWS FRESH S-SW WINDS SOUTH OF 
THE TROUGH AXIS EXTEND AS FAR WEST AS 130W. SW WINDS ASSOCIATED 
WITH THE ACTIVE MONSOON TROUGH ARE BEING FOCUSED BY A STRING OF 
EMBEDDED LOWS IN THE TROUGH. THE LOW NEAR 17N105W APPEARS TO BE 
GAINING MOMENTUM AND GLOBAL MODELS INDICATE FURTHER DEVELOPMENT 
IS POSSIBLE. THE LOW IS FORECAST TO DRIFT NW AT EASTERN END OF 
THE MONSOON TROUGH OVER THE NEXT FEW DAYS. TROPICAL CYCLONE 
FORMATION IS POSSIBLE WITH THIS SYSTEM OVER THE NEXT 2-3 DAYS.

MARINE...
FRESH TO STRONG SW WINDS PERSIST WITHIN 150 NM S OF THE MONSOON 
TROUGH AXIS...AND ARE PRODUCING SEAS TO NEAR 12 FEET BETWEEN 
102W AND 108W. MODEL GUIDANCE SHOWS WINDS INCREASING TO NEAR 30 
KT EARLY MON IN THIS AREA AS THE LOW NEAR 17N105W BECOMES BETTER 
ORGANIZED. LARGE SWELLS WILL CONTINUE TO PROPAGATE FROM SW TO NE 
OVER A BROAD PORTION OF THE AREA THROUGH MONDAY.

$$
MUNDELL