000
AXPZ20 KNHC 162206
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE DEC 16 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...

INTERTROPICAL CONVERGENCE ZONE...6N78W 5N90W 9N105W 9N112W 9N120W
10N127W 7N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
WITHIN 120 NM S OF THE AXIS BETWEEN 118W-121W...BETWEEN 128W-132W
...AND WITHIN 30 NM EITHER SIDE OF THE AXIS BETWEEN 132W-138W. 
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM S OF THE AXIS E OF 
60W.

...DISCUSSION...

RATHER PRONOUNCED AND PROGRESSIVE FLOW REGIME EXISTS OVER THE 
AREA MARKED BY A POSITIVELY-TILTED LONGWAVE TROUGH EXTENDING 
FROM THE NORTHERN U.S. SW THROUGH 32N117W TO 28N131W TO 20N140W. 
A SURFACE COLD FRONT ASSOCIATED WITH THE TROUGH EXTENDS FROM 
NORTHERN BAJA CALIFORNIA SW TO 28N128W WHERE IT BECOMES 
STATIONARY NW TO OUT OF THE AREA AT 32N139W. QUIKSCAT DATA FROM 
NEAR 1500 UTC THIS MORNING ALONG WITH SHIP OBSERVATIONS 
THROUGHOUT THE DAY ALL SHOWED STRONG NW-N WINDS OF 20-25 KT WITH 
SPEEDS NEAR 30 KT ALONG THE FAR NORTHERN PORTION OF THE AREA. 
ALONG WITH THESE WINDS...VERY HIGH SEAS IN THE RANGE OF 15 TO 16 
FT IN N SWELL ARE SPREADING SWD TOWARDS THE NORTHERN PORTION OF 
THE AREA BEHIND THE FRONT. N OF 25N E OF FRONT WINDS ARE SW 20 
KT WITH SEAS TO 8 FT. LATEST MODEL GUIDANCE SUGGESTS THAT A LOW 
WILL FORM ON THE FRONT IN THE VICINITY OF FAR NORTHERN BAJA 
CALIFORNIA AND FAR SOUTHERN CALIFORNIA OVER THE NEXT 24 HOURS AS 
SURFACE PRESSURES DECREASE TO THE E OF THE LONGWAVE TROUGH. THE 
FRONT IS FORECAST TO MOVE INLAND SOUTHERN CALIFORNIA AND 
NORTHERN BAJA CALIFORNIA AND WEAKEN IN ABOUT 36 HOURS AS THE 
ATTENDANT LOW QUICKLY LIFTS NE OVER THE SW U.S. FOLLOWING THE 
AREA OF SYNOPTIC SCALE ASCENT WHICH SHIFTS TO THE WESTERN U.S. 
AT THAT TIME. THE LOW WILL ALLOW FOR SW-W WINDS TO INCREASE TO 
25 KT E OF THE FRONT NEAR NORTHERN BAJA CALIFORNIA ON WED.

THE MAIN IMPACT ON MUCH OF THE AREA WILL BE LINGERING LARGE
SWELLS...IN THE RANGE OF 9-13 FT SPREADING SSE OVER THE WATERS
W OF ABOUT 120W THROUGH THU THEN SUBSIDING TO 8 FT S OF 21N.

GLOBAL MODELS HINT THAT YET ANOTHER PRONOUNCED LONGWAVE TROUGH 
SETS UP OVER THE FAR NE PART OF THE AREA BY FRI WITH AN UPPER
LOW DROPPING SWD INTO THE NORTHERN PORTION OF THE AREA NEAR 
28N130W. THIS LOW IS THEN FORECAST TO CUT-OFF AS IT BECOMES 
LARGER AND DRIFTS SW WHILE A HIGHLY AMPLIFIED UPPER LEVEL RIDGE
REMAINS W OF THE AREA BRINGING CONFLUENT FLOW AND DESCENDING
STABLE AIR IN MODERATE SUBSIDENCE OVER A PORTION OF THE WESTERN
PORTION OF THE AREA.

ELSEWHERE ACROSS THE FORECAST AREA...TRADE WIND CONVERGENCE ZONE
ALONG THE ITCZ REMAINS QUITE ACTIVE FROM 9N-18N W OF 118W WHERE
QUIKSCAT DATA FROM 1500 UTC THIS MORNING SHOWED NE 20-25 KT 
WINDS. STRONGER WINDS WERE NOTED AS RAIN-FLAGGED VECTORS IN
CONVECTION OCCURRING ALONG THIS PORTION OF THE ITCZ. THIS
CONVECTION IS EXPECTED TO REMAIN ACTIVE THROUGH THE END OF THE
WEEK AS UPPER LEVEL DIVERGENCE TO THE SE OF THE TROUGHS CONTINUES
TO SUPPORT THE DEVELOPMENT OF THIS CONVECTION. THERE MAY SOME
INDICATION THAT A WEAK SURFACE TROUGH IS FORMING ALONG OR NEAR 
128W. GLOBAL MODELS EVEN SHOW A POSSIBLE WEAK LOW FORMING THERE
AS WELL OVER THE NEXT 12-18 HOURS. DEEP TROPICAL PACIFIC 
MOISTURE CONTINUES TO STREAM NE TOWARDS BAJA CALIFORNIA...AND
MUCH OF MEXICO.

GAP WINDS...GULF OF PAPAGAYO NE 20-25 KT TO CONTINUE OVER THE 
NEXT 48 HOURS.

$$
AGUIRRE