000
AXPZ20 KNHC 280931
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN OCT 28 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...SPECIAL FEATURE...

A 1006 MB LOW PRES LOCATED NEAR 11.5N111W IS EMBEDDED WITHIN THE 
MONSOON. CONVECTION IS GRADUALLY BECOMING BETTER ORGANIZED IN 
ASSOCIATION WITH THIS LOW. THE CLOUD PATTERN IS EXHIBITING SOME 
BANDING FEATURES. LATEST SATELLITE IMAGERY SHOWS NUMEROUS 
MODERATE TO ISOLATED STRONG CONVECTION WITHIN 180 NM SE AND 90 
NM NW SEMICIRCLES OF LOW CENTER. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS ALSO NOTED ELSEWHERE FROM 12N TO 16N 
BETWEEN 106W AND 113W. THE LOW REMAINS UNDER AN UPPER LEVEL 
ANTICYCLONE...WHICH FAVORS SOME SLOW DEVELOPMENT THROUGH THE 
NEXT 48 HRS WITH A MEDIUM PROBABILITY OF BECOMING A TROPICAL 
CYCLONE WITHIN THE NEXT 48 HRS.

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

MONSOON TROUGH EXTENDS FROM 07N78W NW ALONG THE PACIFIC COAST 
OF PANAMA TO 12N92W TO LOW PRES NEAR 10N100W 1007 MB TO 11N104W 
THEN RESUMES AT 11N111W TO LOW PRES NEAR 11N122W 1007 MB TO 
06N140W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM SE 
QUADRANT OF LOW PRES NEAR 10N110W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS WITHIN 90 NM S OF THE TROUGH 
BETWEEN 112W-118W.

...DISCUSSION...

ALOFT...AN UPPER TROUGH EXTENDS FROM SOUTHERN CALIFORNIA TO 
26N122W. ANTICYCLONIC FLOW DOMINATES MUCH OF THE FORECAST REGION 
S OF 26N E OF 135W WITH ANOTHER RIDGE BUILDING ACROSS THE NW 
WATERS. A SHORT-WAVE TROUGH IS APPROACHING THE FAR WEST PORTION 
OF THE DISCUSSION AREA. A DIFFLUENT PATTERN ALOFT IS HELPING TO 
INDUCE THE CONVECTION ASSOCIATED WITH THE LOW PRES NEAR 
11.5N111W AND THE MONSOON TROUGH.

AT THE SURFACE...A 1024 MB HIGH PRES IS CENTERED NEAR 34N134 
WITH A RIDGE EXTENDING SE TO NEAR 20N118W. THE AREA OF FRESH TO 
STRONG TRADES S OF THE HIGH PRES HAS DIMINISHED OVER THE PAST 
12-24 HOURS...LEAVING SEAS TO 8 FT IN NE SWELL. FEW SHIP 
OBSERVATIONS AND SCATTEROMETER DATA INDICATED THE PRESENCE OF N 
TO NE WINDS IN THE 20-25 KT RANGE N OF 25N BETWEEN 119W AND 130W 
WITH SEAS TO 8 FT. THESE WINDS ARE IN THE PROCESS OF DIMINISHING 
TO LESS THAN 20 KT. RESIDUAL MIXED NE AND SW SWELLS WILL RESULT 
IN 8 FT SEAS FROM 10N-25N W OF 134W. A NEW SET OF NW SWELLS IS 
CURRENTLY PROPAGATING INTO THE NW PORTION OF THE AREA RAISING 
SEAS TO AROUND 9 FT N OF 15N W OF 130W BY THIS AFTERNOON...AND 
CONFINED FROM ABOUT 10-20N W OF 135W BY MON AFTERNOON.

SCATTERED MODERATE CONVECTION ALONG THE MONSOON TROUGH W OF 130W 
HAS LARGELY DIMINISHED AS THE TRADE WIND FLOW SUBSIDED...BUT 
CONTINUES TO BE EVIDENT FARTHER E ASSOCIATED WITH A 1007 MB
LOW PRES NEAR 11N122W...AS WELL AS WITH THE LOW MENTIONED UNDER 
SPECIAL FEATURE. 

GAP WINDS...
A COLD FRONT PUSHING S THROUGH THE SW GULF OF MEXICO IS FOLLOWED 
BY A COOLER AND DRIER AIRMASS. THIS DENSER AIR IS MIXING 
DOWNWARD RESULTING IN N-NE WINDS OF 20-25 KT THROUGH THE GULF OF 
TEHUANTEPEC. OVERNIGHT...A PAIR OF SHIP OBSERVATIONS AND 
SCATTEROMETER DATA CONFIRMED THE PRESENCE OF THESE WINDS SPEEDS. 
HOWEVER...WINDS ARE FORECAST TO INCREASE TO 30 KT THIS MORNING 
AS STRONG WINDS CONTINUE TO FUNNEL THROUGH THE CHIVELA PASS. 
THESE WINDS ARE EXPECTED TO LAST INTO SUN EVENING BEFORE 
DIMINISHING TO 20-25 KT LATE SUN NIGHT AND MON. ACCORDING TO THE 
NOAA III WAVEWATCH GUIDANCE...THE ASSOCIATED SEAS ARE IN THE 
RANGE OF 8-11 FT. THE GFS GLOBAL MODEL AND THE NAM REGIONAL 
MODEL ARE IN AGREEMENT WITH THIS SCENARIO.

$$
GR