000
AXPZ20 KNHC 170340
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT JAN 17 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 IS CENTERED ALONG 4N78W 4N84W 5N91W 4N100W 6N110W 8N120W
6N131W 5N140W. SCATTERED STRONG CONVECTION EXISTS FROM 6N-15N
BETWEEN 111W-115W. STRONG MODERATE CONVECTION IS WITHIN 120 NM N 
OF THE AXIS BETWEEN 100W-105W.

...DISCUSSION...

THE OVERALL PATTERN ACROSS THE REGION HAS SLOW DOWN IN TERMS OF
EASTWARD PROGRESSION OF UPPER LEVEL FEATURES. FOREMOST...A 
MID/UPPER LEVEL CYCLONIC CIRCULATION HAS CUT-OFF OVER SOUTHERN 
CALIFORNIA FROM A PREVIOUS BROAD UPPER LEVEL TROUGH THAT HAS NOW 
PUSHED EASTWARD TO THE EASTERN UNITED STATES. A TROUGH EXTENDS 
WSW FROM THIS CIRCULATION CENTER TO NEAR 32N124W. S OF THIS 
FEATURE...THE AREA REMAINS UNDER MID AND UPPER LEVEL RIDGING E 
OF ABOUT 130W. CONFLUENT FLOW BETWEEN THE CYCLONIC CIRCULATION 
OVER SOUTHERN CALIFORNIA AND FAST ZONAL FLOW E OF 130W IS 
BRINGING MODERATE SUBSIDENCE TO THE FAR NE PART OF THE  
AREA...BUT IS ALSO RESULTING IN EXTENSIVE HIGH LEVEL MOISTURE IN 
THE FROM OF HIGH CLOUDS TO PORTIONS OF SOUTHERN BAJA CALIFORNIA 
AND THE EASTERN PACIFIC BETWEEN SOUTHERN BAJA AND 16N...EAST 
TOWARDS NORTHERN AND CENTRAL MEXICO. A MID/UPPER LEVEL TROUGH 
EXTENDS FROM SE MEXICO NEAR PUERTO ANGEL TO 10N94W.

W OF 130W...A RATHER EXTENSIVE LATITUDINAL DEEP LAYER TROUGH 
STRETCHES ROUGHLY ALONG 133W N OF 16N. TO THE S OF 16N
...IT TURNS SE TO A SMALL MID/UPPER LEVEL CYCLONIC CIRCULATION 
NEAR 13N129W. THE ASSOCIATED SURFACE COLD FRONT IS JUST NW OF 
THE AREA MOVING SE 15 KT...HOWEVER SLY WINDS OF 20 KT PRECEDE 
THE FRONT AS REPORTED BY A FEW SHIPS OVER THE FAR NW WATERS OF 
THE AREA. AN AREA OF BROKEN MULTILAYERED CLOUDS WITH ISOLATED 
WEAK CONVECTION IS ALONG AND WITHIN 360 NM E OF THE TROUGH FROM 
13N-19N.

SATELLITE-DERIVED UPPER LEVEL WINDS SHOW QUITE A LARGE AREA OF 
UPPER LEVEL DIVERGENCE CONTINUING TO ENHANCE MOSTLY SCATTERED
STRONG CONVECTIVE CLUSTERS TO THE E OF THE BASE OF THE TROUGH 
ALONG AND N OF THE ITCZ AXIS GENERALLY CONFINED FROM 6N TO 15N 
BETWEEN 111W AND 115W AS MENTIONED IN FIRST PARAGRAPH UNDER 
ITCZ. EXPECT THIS ACTIVITY TO CONTINUE OVER THE NEXT FEW DAYS AS 
THE TROUGH SLOWLY TRANSLATES EASTWARD. SOME OF THE GLOBAL MODELS 
SUGGEST THAT AN EVENTUAL WEAK LOW MAY EVOLVE FROM THIS AREA AND 
DRIFT NWD OVER THE NEXT 48 HOURS.

MODERATE TO STRONG UPPER LEVEL WINDS ARE ALONG AND W OF THE 
TROUGH AXIS N OF 26N. THESE WINDS CONTINUE TO TRANSPORT UPPER 
LEVEL MOISTURE IN THE FORM OF HIGH LEVEL CLOUDS FROM NEAR THE
HAWAIIAN ISLANDS NNE TO WELL N OF THE REGION. 

THE SURFACE COLD FRONT IS FORECAST TO SLOWLY CLIP THE FAR NW
CORNER OF THE AREA IN ABOUT 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 OR 15 FT OVER THE WEEKEND. ELSEWHERE W OF ABOUT 115W SEAS WILL
BE RATHER CHURNED UP...IN THE 8-14 FT RANGE THROUGH THE NEXT
2 DAYS. WILL MONITOR THIS UPCOMING SWELL EVENT CLOSELY WITH 
RESPECT TO PROJECTED FORECAST HEIGHTS AND AREAL COVERAGE AS 
PORTRAYED IN FUTURE MODEL GUIDANCE.

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 
35-45 KT INTO THE GULF OF TEHUANTEPEC EARLY THIS EVENING. THESE 
WINDS ARE FORECAST TO DECREASE TO ABOUT 25-35 KT IN 24 HOURS...
THEN TO LESS THAN TO 20-30 KT IN 42 HOURS AND TO 20-25 KT IN 
48 HOURS AS INDICATED BY THE LATEST 10M AND 30M MODEL WIND 
GUIDANCE. LONG TERM WIND GUIDANCE INDICATES THAT WINDS MAY REACH
GALE FORCE ONCE AGAIN ON MON.
 
NE WINDS OF 20-25 KT THROUGH THE GULF OF PAPAGAYO ARE EXPECTED 
TO CONTINUE OVER THE NEXT 24 HOURS AS STRONG HIGH PRES RIDGING 
PRESSES SWD OVER CENTRAL AMERICA AND STRONG SW CARIBBEAN TRADES 
ADVECT WESTWARD ACROSS CENTRAL AMERICA. THESE WINDS SHOULD 
DIMINISH TO 20 KT IN ABOUT 48 HOURS. ELSEWHERE HIGH PRES COVERS 
THE AREA N OF ABOUT 15N.

$$
AGUIRRE