000
AXPZ20 KNHC 180336
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN JAN 18 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 3N78W 6N88W 4N97W 5N110W 7N120W
8N130W 5N140W. SCATTERED MODERATE TO STRONG CONVECTION EXISTS 
FROM 9N-14N BETWEEN 105W-108W.

...DISCUSSION...

A MID/UPPER LEVEL TROUGH STRETCHES FROM THE SW U.S. INTO THE AREA
NEAR 32N124W TO 26N131W TO 20N131W TO 17N131W...THEN TURNS E TO
A MID/UPPER LEVEL CYCLONIC CIRCULATION MOVING N 15 KT NEAR 
18N124W. A SURFACE REFLECTION OF THE MID/UPPER LEVEL CIRCULATION 
IS DEPICTED AS A SURFACE TROUGH FROM 14N128W TO 21N127W WITH A
WEAK SURFACE LOW OF 1012 MB ON THE TROUGH AXIS NEAR 19N127W.
THE SURFACE COLD FRONT ASSOCIATED WITH THE MID/UPPER LEVEL
TROUGH IS JUST ENTERING THE NW OF CORNER OF THE AREA WHILE 
MOVING SE 15 KT. SE-S WINDS OF 20-30 KT PRECEDE THE FRONT AS 
REPORTED BY A FEW SHIPS OVER THE FAR NW WATERS OF THE AREA. 
STRONGER S WINDS TO GALE FORCE ARE JUST W OF THE AREA AHEAD OF 
THE FRONT N OF ABOUT 22N. AN AREA OF BROKEN TO OVERCAST 
MULTILAYERED CLOUDS WITH EMBEDDED SCATTERED SHOWERS AND ISOLATED 
TSTMS IS ALONG AND WITHIN 420 NM E OF THE TROUGH FROM 14N-19N.
THIS ACTIVITY IS BEING SUPPORTED BY A LARGE AREA OF UPPER LEVEL 
DIVERGENCE EVIDENT TO THE E OF THE TROUGH.EXPECT THIS ACTIVITY 
TO CONTINUE AT LEAST OVER THE NEXT 48 HOURS. THE 1012 MB LOW IS 
FORECAST TO DRIFT IN A GENERAL WNW DIRECTION OVER THE NEXT 48 
HOURS AS THE TROUGH ALSO MOVES W.

THE MID/UPPER LEVEL CYCLONIC CIRCULATION NEAR 18N124W IS 
FORECAST TO BECOME ABSORBED INTO THE TROUGH...WITH ANOTHER ONE 
POSSIBLY FORMING NEAR 13N121W WITHIN THE NEXT 48-72 HOURS.

THE SURFACE COLD FRONT IS FORECAST TO SLOWLY CLIP THE FAR NW 
CORNER OF THE AREA OVER THE NEXT 24-48 HOURS AS ITS DRIVING 
UPPER SUPPORT AND RELATED ENERGY PULLS FURTHER AWAY FROM THE 
AREA TOWARDS THE GENERAL VICINITY OF ALASKA AS GLOBAL MODELS ARE 
IN PRETTY CLOSE AGREEMENT WITH RESPECT TO THIS SCENARIO. HOWEVER 
...THE MAIN ISSUE WITH THIS FRONT WILL BE LONG PERIOD NW SWELLS 
GENERATED BY ATTENDANT DEEP LOW PRES SYSTEMS THAT WILL PASS WELL 
TO THE N OF 30N UP AND AROUND THE MID/UPPER LEVEL RIDGING 
PRESENT E OF 130W. WAVEWATCH MODEL GUIDANCE IS VERY CONSISTENT 
IN SHOWING SIGNIFICANT WAVE HEIGHTS OF UP TO 19 FT NOW ENTERING 
THE FAR NW CORNER OF THE AREA. THESE SEAS ARE EXPECTED TO 
SUBSIDE TO 14 FT ON SUN. ELSEWHERE W OF ABOUT 115W...SEAS WILL 
BE RATHER CHURNED UP...IN THE 8-14 FT RANGE THROUGH THE NEXT 2 
DAYS.
 
TO THE ENE OF THE TROUGH...MID AND UPPER LEVEL RIDGING IS PRESENT
NE OF LINE 21N129W TO 19N118W TO 14N110W TO NEAR 8N105W. AN AREA
OF DIFFLUENCE TO THE E OF THE RIDGE IS RESULTING IN SCATTERED 
MODERATE TO STRONG CONVECTION FROM 9N-14N BETWEEN 105W-108W. 
OVER THE FAR EXTREME NE SECTION OF THE AREA...CONFLUENT FLOW 
BETWEEN THE PORTION OF THE MID/UPPER TROUGH THAT EXTENDS FROM 
THE SW U.S. INTO THE DISCUSSION AREA...AS DESCRIBED IN THE FIRST 
PARAGRAPH...AND FAST SW-W FLOW OCCURRING TO THE E OF THE RIDGE 
IS BRINGING MODERATE SUBSIDENCE TO THE ALONG AND N OF 30N E OF 
129W. THIS FLOW IS ALSO BRINGING SCATTERED TO BROKEN HIGH LEVEL
CLOUDS TO PORTIONS OF THE EASTERN PACIFIC FROM 18N TO 25N E OF 
122W AND EAST ACROSS NORTHERN AND CENTRAL MEXICO. A MID/UPPER 
LEVEL TROUGH EXTENDS FROM SE MEXICO NEAR PUERTO ANGEL TO 11N94W.

AT THE SURFACE...HIGH PRES RIDGING SWD OVER THE WESTERN GULF 
OF MEXICO AND MEXICO MAINTAINS A TIGHT PRES GRADIENT ALONG THE 
MEXICAN COAST USHERING GALE FORCE WINDS IN THE RANGE OF 30-40 KT 
THROUGH THE GULF OF TEHUANTEPEC THIS EVENING. THESE WINDS ARE 
FORECAST TO DECREASE TO LESS THAN GALE FORCE IN ABOUT 18 HOURS
...THEN INCREASE BACK UP TO GALE FORCE IN 36 HOURS AS INDICATED 
BY THE LATEST 10M AND 30M MODEL WIND GUIDANCE...AND REMAIN
AS A MINIMAL GALE EVENT INTO 48 HOURS AS HIGH PRES OVER SE 
MEXICO WEAKENS.
 
NE 20-25 KT WINDS THROUGH THE GULF OF PAPAGAYO ARE EXPECTED TO 
WEAKEN SLIGHTLY IN 24 HOURS AND CHANGE LITTLE INTO 48 HOURS AS 
PRES GRADIENT OVER CENTRAL AMERICA AND THE WESTERN CARIBBEAN
DOES NOT INCREASE ANY FURTHER. ELSEWHERE HIGH PRES COVERS THE 
AREA GENERALLY N OF 16N WITH A 1021 MB HIGH CENTER NEAR 31N121W
...AND AN ASSOCIATED RIDGE TO 25N131W TO 17N140W.

$$
AGUIRRE