000
AXPZ20 KNHC 120248
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI OCT 12 2012

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...SPECIAL FEATURES...

1008 MB LOW PRES IS EMBEDDED ALONG THE MONSOON TROUGH NEAR 
11.5N104W...OR 520 MILES S OF MANZANILLO MEXICO. THIS LOW HAS 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION WITHIN 240 NM 
IN THE NW QUADRANT. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE 
FOR GRADUAL DEVELOPMENT OF THIS LOW DURING THE NEXT COUPLE DAYS 
AS IT MOVES WESTWARD AT AROUND 10 KT UNDERNEATH UPPER LEVEL 
RIDGING EXTENDING FROM A PARENT ANTICYCLONE OVER CENTRAL MEXICO 
NEAR 20N100W. IN ADDITION...ADDED VORTICITY FROM THE GULF OF 
TEHUANTEPEC THROUGH THE NEXT 48 HOURS ALONG WITH PERSISTENT 
CONVECTION MAY ALSO AID IN THE DEVELOPMENT OF THE LOW.

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

THE MONSOON TROUGH IS ALONG 09N79W TO LOW PRES NEAR 13N93.5W 
1009 MB TO LOW PRES NEAR 11.5N104W 1008 MB TO 11N118W TO 
10N129W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 
10N129W TO 09N140W. SCATTERED MODERATE AND ISOLATED STRONG 
CONVECTION IS WITHIN 120 NM S OF THE MONSOON TROUGH BETWEEN 81W 
AND 84W...AND WITHIN 180 NM N OF THE MONSOON TROUGH BETWEEN 96W 
AND 100W. SCATTERED MODERATE CONVECTION IS FROM 07N TO 10N W OF 
124W...AND ALSO FROM 10N TO 13N BETWEEN 132W AND 138W.

...DISCUSSION...

W OF 110W...A CUTOFF UPPER LEVEL LOW NE OF POINT CONCEPTION 
CALIFORNIA IS MIGRATING NE-E ACROSS SOUTHERN CALIFORNIA. THIS 
UPPER FEATURE AND AN ATTENDANT UPPER TROUGH IS SUPPORTING A COLD 
FRONT EXTENDING FROM CENTRAL ARIZONA TO ACROSS THE NORTHERN GULF 
OF CALIFORNIA. IT IS ALSO SUPPORTING A SURFACE TROUGH TO THE W 
OF THE FRONT FROM E OF SAN DIEGO THROUGH 30N116W TO 26N118W. 
MODEL GUIDANCE INDICATES 20 TO 25 KT SW WINDS IN THE FAR 
NORTHERN GULF OF CALIFORNIA AHEAD OF THE APPROACHING SURFACE 
TROUGH TONIGHT. FOLLOWING THE TROUGH PASSAGE...A SURGE OF 
NORTHERLY WINDS ARE EXPECTED FIRST OVER THE SOUTHERN GULF OF 
CALIFORNIA FRI EVENING...EXPANDING TO THE MAJORITY OF THE GULF 
BY SAT EVENING AS STRONG HIGH PRES DEVELOPS OVER THE U.S. GREAT 
BASIN...AND LOW PRES TROUGHING SETS UP OVER NW MEXICO AND THE 
GULF OF CALIFORNIA REGION. MODERATE TO FRESH NORTHERLY WINDS 
WILL ALSO BE POSSIBLE ALONG THE W COAST OF THE BAJA CALIFORNIA 
PENINSULA FRI EVENING INTO THE WEEKEND.

AN UPPER LEVEL SHORT WAVE TROUGH IS DIGGING E AND SE INTO THE 
FAR NW PORTION OF THE DISCUSSION WATERS...REACHING FROM 32N135W 
TO 22N140W. THIS UPPER FEATURE IS SUPPORTING A LAGGING COLD 
FRONT MOVING JUST N AND W OF 32N. THE SOUTHERN EXTENT OF THIS 
FRONT APPEARS TO BE STALLING HOWEVER...AND WILL LIKELY NOT REACH 
THE DISCUSSION WATERS S OF 30N THROUGH FRI.

THIS SET UP WILL LEAVE A BROAD SURFACE RIDGE OVER THE AREA N 
OF 18N W OF THE MENTIONED SURFACE TROUGH LARGELY IN TACT THROUGH 
THE NEXT 48 HOURS WHICH WILL IN TURN MAINTAIN PRIMARILY MODERATE 
TO FRESH TRADE WIND FLOW ALONG AND S OF THE SOUTHERN EXTENT OF 
THE RIDGE. THE EXCEPTION WILL BE OVER THE W CENTRAL WATERS WHERE 
AN AREA OF FRESH TO STRONG NE TO E WINDS WERE CAPTURED BY 
AFTERNOON ASCAT SCATTEROMETER PASSES. THESE WINDS ARE FORECAST 
TO PERSIST OVER ROUGHLY THE SAME AREA THROUGH THE NEXT 48 HOURS. 
ALSO...THE TRADE WIND FLOW IS ENHANCING CLUSTERS OF CONVECTION 
ALONG THE WESTERN EXTENT OF THE MONSOON TROUGH AND THE ITCZ AS 
IS DESCRIBED IN THE CONVECTION SECTION. 

NW SWELL WITH PEAK WAVE PERIODS OF 15-17 SECONDS CONTINUES TO 
PROPAGATE FROM THE N CENTRAL PACIFIC INTO THE AREA...FROM 10N TO 
21N W OF 123W...AND ALSO OVER THE REMAINDER OF THE AREA N OF 05N 
W OF 135W AS MEASURED BY EARLIER ALTIMETER PASSES. THIS SWELL 
WILL SINK SOUTHWARD REACHING THE EQUATOR BY 24 THROUGH 48 HOURS.

E OF 110W...THE DOMINANT FEATURES ARE TWO LOW PRES AREAS ALONG 
THE MONSOON TROUGH...THE WESTERN LOW OF WHICH IS LISTED IN THE 
SPECIAL FEATURES SECTION. THE EASTERN 1009 MB LOW NEAR 13N93.5W 
HAS ANY ASSOCIATED CONVECTION DISPLACED WELL TO THE W DUE TO 
MODERATE TO STRONG UPPER LEVEL NE TO E SHEAR AND THIS LOW IS NOT 
EXPECTED TO DEVELOP FURTHER UNLIKE THE WESTERN LOW.
 
$$
LEWITSKY