000
AXPZ20 KNHC 190330
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT DEC 19 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...04.5N77W 
TO 07N90W TO 05N104W TO 07N119W TO 07N134W TO 08N140W. NUMEROUS 
MODERATE SCATTERED STRONG WITHIN 180 NM N OF AXIS AND 150 NM S 
OF AXIS E OF 92W. SCATTERED MODERATE ISOLATED STRONG WITHIN 180 
NM N OF AXIS BETWEEN 112W AND 116W. SCATTERED MODERATE ISOLATED 
STRONG WITHIN 80 NM S OF AXIS FROM 121W TO 124W. NUMEROUS 
MODERATE SCATTERED STRONG WITHIN 100 NM EITHER SIDE OF AXIS W OF 
126W. 

...DISCUSSION...

WIDESPREAD CONVECTION WITHIN 100 NM OF ITCZ AXIS W OF 126W IS 
HELPING MAINTAIN UPPER LEVEL RIDGING ACROSS THE W PORTION OF THE 
FORECAST AREA. AN UPPER LEVEL TROUGH PREVAILS ACROSS THE CENTRAL 
PORTION OF THE FORECAST AREA. WIDESPREAD CONVECTION WITHIN 180 
NM OF ITCZ AXIS E OF 92W IS HELPING MAINTAIN UPPER LEVEL RIDGING 
ACROSS THE E PORTION OF THE FORECAST AREA. SW FLOW TO THE E OF 
THE UPPER TROUGH IS ADVECTING MID AND UPPER LEVEL MOISTURE FROM 
THE ITCZ NEAR 116W TO THE YUCATAN PENINSULA. AN UPPER LEVEL LOW 
IS CENTERED NEAR 38.5N148W WITH TROUGHING EXTENDING SW ACROSS 
HAWAII. THE SW FLOW AHEAD OF THE UPPER TROUGH IS ADVECTING MID 
AND UPPER LEVEL MOISTURE ACROSS THE NW PORTION OF THE FORECAST 
AREA...N OF 16N AND W OF 126W. 

AT THE SURFACE...HIGH PRESSURE 1022 MB CENTERED NORTH OF THE 
FORECAST AREA NEAR 32N130W. THE PRESSURE GRADIENT BETWEEN THIS 
FEATURE...AND THE RELATIVELY LOWER PRESSURE IN THE ITCZ 
RESULTING FROM THE ABUNDANT CONVECTION W OF 126W IS MAINTAINING 
FRESH TO STRONG TRADES FROM 08N TO 17N W OF 117W. A TIGHT 
PRESSURE GRADIENT BETWEEN THE HIGH PREVIOUSLY MENTIONED AND LOW 
PRESSURE 990 MB CENTERED NEAR 35N147W IS RESULTING IN FRESH TO 
STRONG SOUTHERLY WINDS IN THE FAR NW PORTION OF THE FORECAST 
AREA. THE HIGH PRESSURE WILL WEAKEN THROUGH THE WEEKEND AS THE 
UPPER LEVEL LOW MENTIONED IN THE PREVIOUS PARAGRAPH SHIFTS 
EASTWARD. AS A RESULT...THE AREAL COVERAGE OF THE FRESH TO 
STRONG TRADEWINDS ACROSS THE W PORTION OF THE AREA WILL 
DECREASE. A COLD FRONT WILL SHIFT INTO THE FAR NW PORTION OF THE 
FORECAST AREA SAT...AND BECOME DIFFUSE BY SUN. THE FRONT HAS 
GENERATED A SET OF LONG PERIOD NW SWELLS WHICH WILL SPREAD INTO 
THE NW PORTION OF THE FORECAST AREA ON SATURDAY...AND SPREAD S 
AND E THROUGH THE WEEKEND. LOW PRESSURE 1009 MB IS CENTERED NEAR 
07N117W. THE LOW IS FORECAST TO DRIFT SLOWLY TO THE NNE. 

GAP WINDS...NORTHERLY WINDS CONTINUE TO FUNNEL THROUGH THE 
ISTHMUS OF TEHUANTEPEC WITH WINDS OF 20 TO 25 KT OVER THE AREA. 
THESE WINDS ARE EXPECTED TO PERSIST THROUGH AT LEAST MONDAY.

THE COMBINATION OF STRONG TRADE WINDS IN THE CARIBBEAN AND LOCAL 
DRAINAGE EFFECTS WILL ALLOW THE FRESH WINDS TO PERSIST THROUGH 
THE GULF OF PAPAGAYO ALSO THROUGH AT LEAST MONDAY.

STRONG HIGH PRESSURE OVER THE GREAT BASIN REGION WILL HELP FOR 
WINDS IN THE GULF OF CALIFORNIA TO INCREASE TO 20 KT BY SAT 
MORNING. THESE WINDS WILL PERSIST THOUGH SUN AFTERNOON AND 
DIMINISH AS THE HIGH WEAKENS. 

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