000
AXPZ20 KNHC 082204
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON DEC 08 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 4N78W 5N90W 7N100W 7N110W 10122W
12N130W 8N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
N OF THE AXIS BETWEEN 104W-106W...AND WITHIN 30 NM OF THE AXIS
BETWEEN 125W-130W.

...DISCUSSION...

A NEARLY STATIONARY WELL-DEFINED MIDDLE/UPPER LEVEL CYCLONIC 
CIRCULATION...ABOUT 5 DEG IN DIAMETER...IS NEAR 21N139W WITH A 
TROUGH EXTENDING SE TO 17N135W AND SW TO W OF THE AREA AT
13N140W. A JET STREAM BRANCH WITH MAXIMUM WINDS OF 60-100 KT 
ENTERS THE AREA AT 11N140W ROUNDING THE BASE OF THE TROUGH
...THEN STRETCHES NE TO 12N130W TO 25N127W AND E TO 28N121W
WHERE IT CONTINUES EASTWARD TOWARDS NORTHERN BAJA CALIFORNIA
TO ACROSS NORTHERN MEXICO AND NE ACROSS THE CENTRAL U.S.
MARKING THE SOUTHERN PORTION OF A LONGWAVE TROUGH THAT COVERS 
MUCH OF THE WESTERN U.S. THE FAR SW TAIL END OF THIS TROUGH 
EXTENDS SW TO THE MID/UPPER LEVEL CYCLONIC CIRCULATION NEAR
21N139W. ANOTHER BRANCH OF THE JET STREAM SPLITS OFF THE FIRST 
ONE NEAR 18N128W AND DIVES SE THROUGH 17N118W TO 14N110W TO 
5N106W. AT THE SURFACE...A TROUGH ASSOCIATED WITH THE MID/UPPER
LEVEL CYCLONIC CIRCULATION IS ANALYZED ALONG 149W FROM 20N TO 
26N. THE INTERACTION BETWEEN THE TROUGH AND HIGH PRES TO THE N 
HAS TIGHTEN THE PRES GRADIENT FROM 19N TO 25N BETWEEN 122W AND 
125W WHERE NE-E 20 TO 25 KT WINDS ARE BEING OBSERVED. THESE 
WINDS ARE FORECAST TO DIMINISH TO 20 KT IN ABOUT 24 HOURS
UNTIL THE TROUGH MOVES W OF THE AREA DURING THE NEXT 24-36 
HOURS. SCATTERED SHOWERS ARE NOTED WITHIN 120 NM E OF THE TROUGH
FROM 20N TO 22N. A SURFACE RIDGE AXIS ENTERS THE DISCUSSION AREA 
THROUGH 32N129W AND EXTENDS THROUGH 25N120W TO 20N109W. HIGH
PRES COVERS THE AREA N OF 19N W OF 110W.

TO THE E OF THE ABOVE MENTIONED MID/UPPER CYCLONIC CIRCULATION
AND TROUGH....MID/UPPER LEVEL RIDGING IS NOTED OVER THE AREA S 
OF 25N BETWEEN 106W-124W WITH A MEAN AXIS ROUGHLY ALONG 115W. 
WHERE THE JET STREAM MAKES ITS TURN TO THE NE AT 128W...A SPLIT 
FLOW PATTERN EXISTS WITH ANOTHER BRANCH OF THE JET STREAM DIVING 
SE THROUGH 19N114W TO 10N106W. A ZONE OF UPPER LEVEL DIFFLUENCE 
CONTINUES TO ENHANCE THE AREA OF CLOUDS FROM 13N-25N BETWEEN 
127W-134W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
EMBEDDED WITHIN THIS AREA FROM 14N-17N BETWEEN 129W-132W.
A SURFACE TROUGH IS ANALYZED ALONG 121W/122W FROM 7N-14N. 
MODERATE SUBSIDENCE WITH ASSOCIATED DRY STABLE CONDITIONS IS 
ENTERING THE FAR WESTERN PORTION OF THE AREA BEHIND THE UPPER 
LOW AND TROUGH. STRONG SUBSIDENCE AND RATHER STABLE CONDITIONS 
ARE PRESENT OVER THE EASTERN PORTION OF THE AREA E OF ABOUT 104W.

LATEST SATELLITE IMAGERY CONTINUES TO SHOW AMPLE MID AND UPPER 
LEVEL SUB-TROPICAL MOISTURE IN THE FORM OF MIDDLE AND HIGH 
BROKEN TO OVERCAST CLOUDS STREAMING NORTHEASTWARD FROM THE 
CENTRAL PACIFIC NE OVER AND OVER THE AREA OF MID/UPPER
LEVEL RIDGING TOWARDS MUCH OF MEXICO...INCLUDING BAJA CALIFORNIA 
S OF 28N. AT THE SURFACE...A TROUGH IS ANALYZED FROM 15N127W
TO 9N128W. LATEST VISIBLE SATELLITE IMAGERY SHOWS A WEAK LOW 
FORMING NEAR 11N129W. THE INTERACTION BETWEEN THE TROUGH AND 
HIGH PRES TO THE N CONTINUES TO TIGHTEN THE PRES GRADIENT FROM 
12N TO 19N BETWEEN 118W AND 135W WHERE NE-E WINDS OF 20 TO 25 KT 
ARE OCCURRING. THESE WINDS ARE FORECAST TO EXPAND OUTWARD TO THE 
NE OF THE LOW FORECAST TO BE NEAR 14N1209 IN 24 HOURS...AND NEAR 
15N130W AT 48 HOURS. ELSEWHERE FROM ABOUT 17N TO 27N W OF 128W 
TRADES ARE EXPECTED TO BE NE-E WINDS TO 20 KT THROUGH AT LEAST 
THE NEXT 48 HOURS.

THE CURRENT PATTERN WILL BEGIN TO CHANGE BY THU AS THE MID/UPPER
LEVEL CYCLONIC CIRCULATION BEGINS TO LIFT NE TOWARDS THE FAR 
NORTHERN PORTION OF THE AREA WITH RIDGING AT ALL LEVELS 
PREDOMINATELY COVERING JUST ABOUT THE ENTIRE AREA.

GAP WINDS...GULF OF PAPAGAYO NE 20 KT WINDS ARE EXPECTED TO 
DIMINISH IN ABOUT 24-36 HOURS. GULF OF TEHUANTEPEC N-NE 20 KT
WINDS ARE FORECAST TO DIMINISH TO LESS THAN 20 KT SHORTLY.
LATEST NWP MODEL GUIDANCE INDICATES THAT WINDS WILL 
SUBSTANTIALLY INCREASE IN THE GULF BEGINNING WED NIGHT 
SIGNIFYING THE ONSET OF THE NEXT GALE EVENT AS STRONG HIGH PRES 
SURGES SWD THROUGH CENTRAL AND SOUTHERN MEXICO BEHIND THE NEXT 
STRONG COLD FRONT EXPECTED TO PUSH OFF THE TEXAS COAST AND INTO 
THE WESTERN GULF OF MEXICO TUE NIGHT.

$$
AGUIRRE