000
AXPZ20 KNHC 172205
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU DEC 17 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...
THE ITCZ AXIS 06N77W TO 07N90W TO 05N104W TO 06N125W TO 07N140W. 
SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF THE 
ITCZ AXIS BETWEEN 82W AND 89W AS WELL AS WITHIN 120 NM N OF THE 
ITCZ AXIS BETWEEN 120W AND 124W. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION WITHIN 120 NM N OF THE ITCZ AXIS W OF 
136W.

...DISCUSSION...
AN AMPLIFIED NORTHERN STREAM PATTERN IS IN PLACE OVER THE 
NORTHERN PORTION OF THE FORECAST AREA. A MEAN UPPER TROUGH 
CENTERED ALONG 105W N OF 17N WITH TWO SPOKES ON THE EASTERN AND 
WESTERN SIDES OF THE AXIS...WITH ONE SPOKE FROM FROM THE TEXAS 
BIG BEND THROUGH EASTERN MEXICO AND ANOTHER FROM CENTRAL ARIZONA 
SW TO NEAR 25N 125W ASSOCIATED WITH SHORTWAVE ENERGY MOVING INTO 
THE BACKSIDE OF THE MEAN TROUGH. FARTHER W...THE MEAN RIDGE AXIS 
CAN BE FOUND FROM 30N125W TO 10N140W. THIS PATTERN IS EXPECTED 
TO REMAIN STATIONARY AND AMPLIFY SLIGHTLY OVER THE NEXT FEW 
DAYS. THE INCREASED AMPLIFICATION WILL MAKE ROOM FOR THE NEXT 
TROUGH AND ASSOCIATED SURFACE COLD FRONT TO MOVE INTO NW WATERS 
SAT BRINGING A NEW BATCH OF NW SWELL BUT LITTLE IN THE WAY OF 
WIND OR PRECIPITATION. THIS ADVANCING COLD FRONT WILL ACT TO 
WEAKEN THE SURFACE RIDGE SLIGHTLY AND ALLOW IT TO DRIFT 
NORTHWARD A FEW DEGREES. THIS WILL CAUSE THE 20 TO 25 KT TRADE 
WINDS FOUND PRIMARILY BETWEEN 07N AND 13N W OF 118W BETWEEN THE 
RIDGE AXIS AND SURFACE TROUGH ALONG 135W FROM 04N TO 11N TO 
WEAKEN AND SHIFT W THROUGH SAT. 

ANOTHER SURFACE TROUGH EXTENDS FROM 11N115W TO 1008 MB LOW PRES 
07N116W TO 03N115W. THERE IS A DECIDED LACK OF DEEP CONVECTION 
NEAR THIS LOW AS THE SOUTHERN STREAM WESTERLY UPPER JET LIES 
JUST N OF THE LOW. TOTAL PRECIPITABLE WATER SATELLITE IMAGERY 
SHOWS THAT THE LOW TO MID LEVEL MOISTURE IS POOLED A FEW DEGREES 
TO THE W OF THIS TROUGH. AS MENTIONED IN THE ITCZ SECTION...THIS 
MOISTURE IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION WITHIN 
120 NM N OF THE ITCZ AXIS BETWEEN 120W AND 124W. THIS LOW IS 
EXPECTED TO PERSIST FOR THE NEXT FEW DAYS...BUT REMAIN 
RELATIVELY STATIONARY AND WEAKEN SLIGHTLY THROUGH SAT.

CLOSER TO LAND...ASCAT SHOWS N WINDS AROUND 20 KT RANGE CONTINUE 
IN THE GULF OF CALIFORNIA AT THE MOMENT. THESE WINDS WILL 
PERSIST DUE TO THE GRADIENT BETWEEN CLIMATOLOGICAL LOW PRES OVER 
THE EASTERN GULF OF CALIFORNIA AND PERSISTENT HIGH PRES OVER THE 
GREAT BASIN.

GAP WINDS..GAP WINDS PERSIST THROUGH THE GULFS OF PAPAGAYO AND 
TEHUANTEPEC. THE COMBINATION OF STRONG TRADE WINDS IN THE 
CARIBBEAN AND LOCAL DRAINAGE EFFECTS WILL ALLOW THE FRESH WINDS 
TO PERSIST IN PAPAGAYO THROUGH TONIGHT. WINDS AT OR ABOVE GALE 
FORCE CAN BE FOUND IN THE GULF OF TEHUANTEPEC BUT ARE EXPECTED 
TO DIMINISH BELOW GALE FORCE BY THIS TIME TOMORROW.

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