000
AXPZ20 KNHC 280330
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON DEC 28 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 
0300 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...05N77W TO 
04N105W TO 08N118W TO 06N140W. SCATTERED MODERATE TO ISOLATED 
STRONG CONVECTION IS FROM 06N TO 09N W OF 129W. 

...DISCUSSION...

ALOFT...ZONAL FLOW PREVAILS ACROSS MUCH OF THE FORECAST AREA 
WITH A SHORTWAVE TROUGH MOVING EWD ACROSS THE N WATERS. THE 
TROUGH AXIS IS CURRENTLY N OF 23N ALONG 125W. A JET STREAM 
BRANCH WITH CORE WINDS OF 90-110 KT ROUNDS THE BASE OF THIS 
SHORTWAVE TROUGH. ABUNDANT MID AND UPPER LEVEL MOISTURE IS N OF 
21N EAST OF THE TROUGH AXIS EXTENDING ACROSS NORTHERN MEXICO 
INTO TEXAS. THE SHORTWAVE IS FORECAST TO MOVE EAST ABOUT 30 
KNOTS AND STRENGTHEN REACHING THE BAJA CALIFORNIA PENINSULA  
LATE MONDAY. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE AND 
IMPLIED DRY AIR MASS COVERS MUCH OF THE AREA W OF 100W WITH THE 
EXCEPTION OF THE CONVECTION ASSOCIATED WITH THE ITCZ. AN UPPER 
LEVEL ANTICYCLONE CENTERED OVER THE SOUTH-CENTRAL CARIBBEAN 
EXTENDS A RIDGE ACROSS THE E PART OF THE FORECAST AREA E OF 
100W. 

AT THE SURFACE...A WEAKENING COLD FRONT ASSOCIATED WITH THE 
ABOVE MENTIONED SHORTWAVE TROUGH IS ACROSS THE NW PORTION OF THE 
FORECAST AREA ALONG 30N131W 24N135W 23N140W. SOME SHIP REPORTS 
AND AN EARLIER ASCAT PASS SHOWED N WINDS IN THE 20 TO 25 KT 
RANGE BEHIND THE FRONT. THE COLD FRONT WILL CONTINUE TO 
DISSIPATE...AND THE SURFACE HIGH PRESSURE CENTERED NEAR 31N138W 
WILL SHIFT E BEHIND THE FRONT MAINTAINING THE AREA OF FRESH TO 
STRONG TRADE WINDS BETWEEN 08N AND 21N W OF 125W THROUGH AT 
LEAST TUE. WINDSAT AND ASCAT DATA INDICATED TRADE WINDS OF 20 
TO 25 KT IN THIS AREA.  

SEAS CONDITIONS ARE DOMINATED BY LONG PERIOD NW SWELL (WAVE 
PERIODS OF UP TO 18 SECONDS) WITH SIGNIFICANT WAVE HEIGHTS AS 
HIGH AS 17 FT PARTICULARLY OVER THE NW CORNER OF THE AREA. NOAA 
WAVE WATCH III GUIDANCE SUGGESTS THAT THIS SWELL EVENT WILL 
CONTINUE TO SPREAD SE REACHING NEAR 100W IN ABOUT 48 HOURS.
 
GAP WINDS...
BASED ON THE NAM AND GFS COMPUTER MODELS...N WINDS ARE EXPECTED 
TO INCREASE TO 20 TO 30 KT ACROSS THE GULF OF TEHUANTEPEC OVER 
THE NEXT 24 HOURS AS HIGH PRES BUILDS ACROSS THE EASTERN SLOPES 
OF THE SIERRA MADRE MOUNTAINS IN MEXICO.

E WINDS ARE FORECAST TO INCREASE TO 20 TO 25 KT ACROSS THE GULF 
OF PAPAGAYO DURING THE NEXT COUPLE OF DAYS AND SPREAD WWD BY TUE 
AS FRESH TRADE WIND FLOW IN THE SW CARIBBEAN FUNNELS THROUGH THE 
GAP. THE WINDS ARE GREATEST DURING THE OVERNIGHT AND EARLY 
MORNING HOURS WITH THE AID OF DRAINAGE FLOW. 

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
$$
GR