000
AXPZ20 KNHC 282138
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI OCT 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2015 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 10N84W TO 07N88W TO 
12N123W TO 11N128W. THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS 
ANALYZED FROM 11N128W TO 08N140W. SCATTERED MODERATE CONVECTION 
IS WITHIN 120 NM S OF AXIS BETWEEN 106W AND 110W WHILE ISOLATED 
MODERATE CONVECTION IS WITHIN 120 NM S OF AXIS BETWEEN 122W AND 
139W. SCATTERED MODERATE CONVECTION ALSO LIES FROM 10N TO 20N 
BETWEEN 120W AND 130W.

...DISCUSSION...

AN UPPER LOW IS OVER THE NW PORTION OF THE AREA NEAR 28N135W. 
THIS LOW IS PART OF A MEAN TROUGH THAT EXTENDS W TO THE HAWAIIAN 
ISLANDS. ENERGY OVER THAT WESTERN PORTION OF THE TROUGH WILL 
SINK SOUTHWARD OVER THE NEXT FEW DAYS AND EJECT THE UPPER LOW 
NORTHWARD AND OUT OF THE FORECAST AREA. UNTIL THEN...THE MAIN 
IMPACT ON THE SENSIBLE WEATHER OVER THE PACIFIC WILL BE CLOUDS 
AND SHOWERS OVER N CENTRAL WATERS. UPPER LEVEL DIFFLUENCE AND 
SHOWER ACTIVITY ARE CURRENTLY MOST PREVALENT IN THE REAR RIGHT 
QUADRANT OF THE 50-66 KT SOUTHERLY JET ON THE SE SIDE OF THE 
UPPER LOW...WITH SCATTERED MODERATE CONVECTION FROM 10N TO 20N 
BETWEEN 120W AND 130W. WATER VAPOR IMAGERY SHOWS THE MOISTURE 
TRANSPORT ALOFT FROM THE TROPICS INTO THE LOW WITH DRY AIR 
WRAPPING AROUND THE WESTERN AND SOUTHERN SIDES OF THE LOW. 
CIRRUS ON THE E SIDE OF THE LOW IS BEGINNING TO MAKE ITS WAY 
INTO BAJA CALIFORNIA. 

THE 1025 MB SUBTROPICAL HIGH LIES NEAR 35N132W AND EXTENDS A 
RIDGE AXIS SE TO 20N120W. THE PRES GRADIENT BETWEEN THE SW SIDE 
OF THE RIDGE AND THE ITCZ/MONSOON TROUGH IS STRONG ENOUGH TO 
YIELD FRESH TRADE WINDS OVER WATERS W OF 123W. THESE TRADES WILL 
VARY LITTLE OVER THE NEXT FEW DAYS AS THE SUBTROPICAL HIGH 
POSITION AND STRENGTH REMAINS MOSTLY UNCHANGED. 

THE 1420 UTC ASCAT PASS SHOWED FRESH SW FLOW S OF THE MONSOON 
TROUGH OVER THE FAR SE PORTION OF THE AREA S OF PANAMA. THESE 
WINDS ARE EXPECTED TO CONTINUE FOR THE NEXT DAY OR TWO AS THE 
PRES GRADIENT REMAINS TIGHT BETWEEN TROUGHING OVER THE WESTERN 
CARIBBEAN AND RIDGING S OF THE EQUATOR IN THE EASTERN PACIFIC. 
SCATTERED MODERATE CONVECTION CAN ALSO BE FOUND N OF 03N E OF 
82W WITH SOME MODERATE TO STRONG CONVECTION MOSTLY ONSHORE OVER 
PANAMA. 

A COLD FRONT IS MAKING ITS WAY THROUGH EASTERN MEXICO AND THE 
WESTERN GULF OF MEXICO. HIGH PRES BEHIND THE FRONT WILL MIGRATE 
EASTWARD FROM THE U.S. FOUR CORNER STATES OVERNIGHT AS THE FRONT 
CONTINUES E. FRESH NW TO N WINDS ARE BLOWING ACROSS THE GULF OF 
CALIFORNIA ACCORDING TO THE EXPERIMENTAL 1737 UTC ASCAT 25 KM 
COASTAL WINDS. SHIPS ZCDF4...3EUS...AND ELWR5 HAVE ALL REPORTED 
FRESH WINDS FROM CABO CORRIENTES N TO THE MOUTH OF THE GULF OVER 
THE LAST FEW HOURS AS WELL. THESE WINDS ARE FORECAST TO DIMINISH 
BELOW 20 KT OVERNIGHT AS HIGH PRES OVER THE FOUR CORNERS STATES 
WEAKENS AND THE PRES GRADIENT RELAXES OVER THE REGION.

GAP WINDS...THE AFOREMENTIONED COLD FRONT WILL MOVE THROUGH THE 
SW GULF OF MEXICO BY SUNSET RESULTING IN A SURGE OF STRONG 
NORTHERLY WINDS WHICH WILL FUNNEL THROUGH THE CHIVELA PASS INTO 
THE GULF OF TEHUANTEPEC THIS EVENING. THESE WINDS WILL RAPIDLY 
INCREASE TO GALE FORCE TONIGHT CONTINUING THROUGH SUN MORNING. 
EXPECT THE STRONGEST WINDS...IN THE 30 TO 40 KT RANGE...BY SAT 
EVENING WITH SEAS BUILDING TO AROUND 15 FT. LOOKING AHEAD...GALE 
CONDITIONS ARE EXPECTED TO DIMINISH BRIEFLY ON SUN...WITH A 
RECURRENCE MON AS ANOTHER SPOKE IN THE EASTERN NORTH AMERICA 
MEAN TROUGH SWINGS THROUGH THE GULF OF MEXICO.

$$
SCHAUER