000
AXPZ20 KNHC 090957
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE NOV 08 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

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

THE MONSOON TROUGH EXTENDS SW ACROSS COSTA RICA FROM 10N83W TO 
THE E PACIFIC AT 08N90W AND CONTINUES W TO NEAR 08N103W WHERE 
LOW LEVEL WINDS INDICATE A TRANSITION TO THE AN ITCZ WHICH THEN 
TURNS NW TO NEAR 13N117W. A LOW LEVEL TROUGH IS ORIENTATED NNE 
TO SSW FROM 10N120W TO 15N112W...AND IS ACCOMPANIED BY SCATTERED 
MODERATE ISOLATED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF 
ITS AXIS. THE ITCZ AXIS RESUMES W OF THE TROUGH NEAR 10N121W AND 
MEANDERS BETWEEN 08N AND 10N TO BEYOND 10N140W. ISOLATED 
MODERATE CONVECTION IS S OF THE MONSOON TROUGH WITHIN 150 NM 
EITHER SIDE OF A LINE FROM 06N77W TO 06N87W TO 08N96W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 30 NM OF 
10N113W AND WITHIN 60 NM EITHER SIDE OF A LINE FROM 09N127W TO 
09N139W.

...DISCUSSION...

A LONG WAVE TROUGH DOMINATES CENTRAL N AMERICA WITH AN EMBEDDED 
SHORT WAVE TROUGH SHIFTING SE THROUGH THE PATTERN OVER THE 
DISCUSSION AREA TO THE N OF 25N BETWEEN 105W AND 120W. A BAND OF 
UPPER MOISTURE IS RACING E ACROSS THE NORTHERN BAJA CALIFORNIA 
PENINSULA...THE NORTHERN GULF OF CALIFORNIA AND EXTREME NORTHERN 
OLD MEXICO THIS MORNING. A BAND OF VERY DRY UPPER AIR...ROUGHLY 
WITHIN 120 NM EITHER SIDE OF A LINE FROM 28N125W TO 35N120W IS 
RACING E IN THE WAKE OF THE MOISTURE BAND...AND WILL MOVE ACROSS 
THE SAME NE PORTIONS LATER TODAY. 

AN UPPER LEVEL CYCLONE CONTINUES OVER THE DEEP TROPICS NEAR 
01N105W AND SEPARATES UPPER ANTICYCLONIC FLOW OVER THE TROPICAL 
E PACIFIC. TO THE W AN UPPER ANTICYLONE IS CENTERED NEAR 12N128W 
WITH A SHORT WAVE RIDGE AMPLIFYING N BEYOND 32N128W TO ALONG THE 
WESTERN SEABOARD OF THE CONUS. AN UPPER ANTICYCLONE IS CENTERED 
NEAR 13N90W WITH A RIDGE EXTENDING NE ACROSS THE EASTERN GULF OF 
MEXICO AND THE SE CONUS. BROAD UPPER DIFFLUENCE IS ENHANCING THE 
PREVIOUSLY DESCRIBED CONVECTION ALONG THE LOW LEVEL TROUGH AND 
ALONG THE ITCZ BETWEEN 120W AND 140W. THE DEBRIS MOISTURE IS 
ADVECTED N MERGING WITH ADDITIONAL MOISTURE ORIGINATING FROM 
ITCZ CONVECTION BETWEEN 140W AND 158W THAT HAS SPREAD E INTO THE 
DISCUSSION AREA. THE RESULT IS FAIRLY MOIST UPPER LEVELS FROM 
05N TO 28N BETWEEN 123W AND 145W. SOME OF THIS MOISTURE 
CONTINUES E ALONG THE BASE OF THE UPPER TROUGH...AND WILL SPREAD 
E ACROSS THE SOUTHERN BAJA PENINSULA AND GULF OF CALIFORNIA 
TODAY. DEBRIS MOISTURE FROM CONVECTION ALONG THE MONSOON TROUGH 
FANS OUT OVER THE AREA FROM THE EQUATOR TO 09N TO THE E OF 90W. 
OF SIGNIFICANCE IS A STRONG UPPER SHORTWAVE IS APPROACHING THE 
NW PORTION WITH ITS AXIS CURRENTLY ALONG 32N140W TO 28N146W.  

AT THE LOW LEVELS A SURFACE HIGH IS NEAR 32N127W IS SHIFTING E 
ALONG 32N WITH A RIDGE EXTENDING SE TO NEAR 16N108W. SOUTHERLY 
WINDS ARE INCREASING TO 15 TO 20 KT OVER THE WATERS N OF 29N W 
OF 138W IN ADVANCE OF A SURFACE COLD FRONT THAT WILL MOVE INTO 
THE AREA LATER TODAY ACCOMPANIED BY NW WINDS AT 20 TO 25 KT AND 
SEAS TO 9 FT IN NW SWELL. SOUTHERLY WINDS WILL ALSO INCREASE TO 
20 TO 25 KT OVER THE WATERS N OF 28N WITHIN 240 NM E OF THE 
FRONT. ALTHOUGH THE GRADIENT WILL RELAX ON THU AND FRI...LARGE 
NW SWELLS... RESULTING IN COMBINED SEAS TO 20 FT...WILL 
PROPAGATE SE INTO THE NW WATERS. NE TO E TRADE WINDS AT 15 TO 20 
KT AND SEAS 9 TO 11 FT IN MIXED NE AND NW SWELL...IS OBSERVED S 
OF THE RIDGE IN THE AREA FROM 08N TO 25N W OF 115W. MIXED N 
SWELL IS FOUND OVER THE REMAINDER OF FORECAST WATERS W OF 110W 
WITH SEAS 7 TO 10 FT IN THE N SWELL WHICH IS MIXING WITH 
SOUTHERLY SWELL IN WATERS S OF 12N.

GULF OF CALIFORNIA...NORTHERLY WINDS AT 20 TO 25 KT ARE 
EXPECTED TO DIMINISH TO 20 KT ON THU AND BELOW 20 KT ON 
FRI.

GULF OF TEHUANTEPEC...N WINDS AT 15 TO 20 KT WILL SURGE THROUGH 
THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC TONIGHT RAPIDLY 
INCREASING TO GALE FORCE THU AFTERNOON...AND JUST BELOW STORM 
FORCE THU NIGHT. WINDS WILL DIMINISH BELOW GALE FORCE FRI NIGHT 
AND FURTHER DIMINISH BELOW 20 KT SAT.

$$
NELSON