000
AXPZ20 KNHC 292116
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT OCT 29 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 
1945 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS IS ANALYZED FROM 10N85W TO 08N92W TO 
08N107W TO 10N115W TO 10N124W. INTERTROPICAL CONVERGENCE ZONE 
AXIS IS ANALYZED FROM 10N124W TO 11N128W TO 09N140W. SCATTERED 
MODERATE CONVECTION LIES E OF 88W WITHIN 120 NM N OF AXIS AND S 
OF AXIS TO 03N. 

...DISCUSSION...

A RAPIDLY WEAKENING UPPER LOW OVER THE NW PORTION OF THE AREA 
SHOULD FINALLY BE DRAWN NORTHEASTWARD INTO A TROUGH AMPLIFYING 
OVER THE WESTERN U.S. BEGINNING SUN NIGHT. WATER VAPOR IMAGERY 
CURRENTLY SHOW MOISTURE BEING ADVECTED FROM THE TROPICS TOWARD 
THIS LOW...WITH WIDESPREAD CIRRUS AND ALTO-STRATUS FOUND 
PRIMARILY FROM 17N TO 30N BETWEEN 118W AND 129W AS WELL AS OVER 
CENTRAL BAJA CALIFORNIA AND THE CENTRAL GULF OF CALIFORNIA. AS 
THE LOW WEAKENS AND MOVES NE...THE CLOUDINESS HERE WILL WANE. 
THIS LOW IS PART OF A WEAKENING MEAN TROUGH THAT EXTENDS W TO 
THE HAWAIIAN ISLANDS. ANOTHER UPPER LOW WITHIN THE TROUGH LIES 
JUST W OF THE AREA AND E OF THE BIG ISLAND OF HAWAII. THIS LOW 
IS EXPECTED TO DRIFT E...WITH SOME UPPER LEVEL CLOUDS MOVING 
INTO W WATERS PRIMARILY N OF 15N THROUGH MON. 

THE 1026 MB SUBTROPICAL HIGH LIES NEAR 35N134W AND EXTENDS A 
RIDGE AXIS SE TO 20N115W. 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 125W BETWEEN 13N AND 
21N ACCORDING TO THE 1858 UTC ASCAT PASS. THESE TRADES WILL VARY 
LITTLE THROUGH SUN AS THE SUBTROPICAL HIGH POSITION AND STRENGTH 
REMAINS MOSTLY UNCHANGED. ON MON...THE HIGH IS EXPECTED TO MERGE 
WITH A STRONGER HIGH TO ITS NW. THIS WILL SHIFT THE AREA OF 
FRESH TRADE WINDS SLIGHTLY FARTHER W.

THE 1540 UTC ASCAT PASS SHOWED FRESH SW FLOW S OF THE MONSOON 
TROUGH OVER THE FAR SE PORTION OF THE AREA S OF PANAMA. 
SHIPS A8MW6 AND A8SF8 BOTH REPORTED FRESH SW WINDS IN THIS AREA 
AS WELL. 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. THE STRENGTH OF THE WINDS HERE WILL LARGELY BE 
TIED TO THE STRENGTH OF THE TROUGHING IN THE CARIBBEAN. 
SCATTERED MODERATE CONVECTION FOUND OVER MUCH OF THE AREA 
OFFSHORE OF COLOMBIA...PANAMA...AND COSTA RICA IS DESCRIBED IN 
THE SECTION ABOVE. THIS CONVECTION EXTENDS INLAND OVER MUCH OF 
PANAMA...COSTA RICA...AND EASTERN NICARAGUA WITH SOME ISOLATED 
AREAS OF STRONG CONVECTION FOUND INLAND. THIS AREA LIES UNDER 
UPPER LEVEL DIFFLUENCE ASSOCIATED WITH A RIDGE AXIS THAT EXTENDS 
TO AN ANTICYCLONE OVER EASTERN CUBA AND WITHIN THE REGION OF 
HIGHEST PRECIPITABLE WATER VALUES IN THE FORECAST AREA. 
WIDESPREAD PRECIPITATION SHOULD CONTINUE HERE THROUGH MON.

GAP WINDS...THE 1538 UTC ASCAT PASS FAILED TO SHOW WINDS TO GALE 
FORCE IN THE GULF OF TEHUANTEPEC. HOWEVER...ENHANCEMENT OF THE 
WINDS EXPECTED HERE WITH NIGHTTIME DRAINAGE FLOW FROM THE 
MOUNTAINS AND A SURGE OF COLDER AND MUCH DRIER AIR CURRENTLY 
MAKING ITS WAY S THROUGH THE WESTERN GULF OF MEXICO AND EXPECTED 
TO REACH CHIVELA PASS SUN WILL HELP KEEP WINDS HOVERING NEAR 
GALE FORCE THROUGH MON. THE GALE WARNING WILL CONTINUE TO BE IN 
EFFECT THROUGH THE END OF THE FORECAST PERIOD MON AFTERNOON.

$$
SCHAUER