000
AXPZ20 KNHC 041001
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI DEC 04 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0815 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG A LINE FROM 07N77W TO 07N100W TO 08N110W 
TO 09N122W TO 06N140W. SCATTERED MODERATE CONVECTION CAN BE 
FOUND WITHIN 120 NM S OF THE AXIS E OF 79W AND WITHIN 120 NM N 
OF THE AXIS BETWEEN 120W TO 122W.

...DISCUSSION...
AN AMPLIFIED UPPER PATTERN IS IN PLACE OVER THE FORECAST AREA N 
OF 20N...WITH AN UPPER LOW NEAR 23N137W EXPECTED TO PASS TROUGH 
THE RIDGE AXIS TO ITS E OVER THE NEXT 24 HOURS AND MOVE INTO THE 
SW EDGE OF THE MEAN BROAD TROUGH OVER NORTH AMERICA. THE PASSAGE 
OF THIS SHORTWAVE ENERGY THROUGH THE UPPER RIDGE WILL HELP KEEP 
THE SURFACE RIDGING ON THE WEAK SIDE OVER NORTH 
WATERS...REDUCING THE EASTERLY TRADE WINDS TO 20 KT GENERALLY IN 
THE REGION FROM 10N-20N W OF 125W THE NEXT FEW DAYS. TO THE W OF 
THE UPPER RIDGE AXIS CENTERED OVER THE CENTRAL N PACIFIC LIES 
ANOTHER MEAN UPPER TROUGH. A SERIES OF SHORTWAVE SYSTEMS WILL 
MOVE NORTHEASTWARD IN THE LEADING EDGE OF THIS BROAD TROUGH OVER 
THE NEXT FEW DAYS. THE FIRST IS CURRENTLY DISSIPATING JUST NW OF 
THE FORECAST AREA AND HAS BROUGHT NW SWELL IN THE 8 TO 11 FT 
RANGE TO NW WATERS WHILE A SECOND IS EXPECTED TO DRAG ITS 
ASSOCIATED COLD FRONT INTO FAR NW WATERS IN ABOUT 48 HOURS. LOOK 
FOR THE NW SWELL TO DAMPEN AS IT SPREADS SOUTHWARD WHILE A NEW 
BATCH OF NW SWELL WILL INCREASE SEAS ONCE AGAIN TO THE 8 TO 10 
FT RANGE OVER NW WATERS NEAR THE WEAKENING FRONTAL BOUNDARY AT 
THE END OF THE PERIOD.

S OF 20N...TWO LOW PRES SYSTEMS AND A SURFACE TROUGH ARE 
EMBEDDED WITHIN THE ITCZ. THE SURFACE TROUGH FROM 12N123W TO 
07N126W IS THE MOST CONVECTIVELY ACTIVE...WITH SCATTERED 
MODERATE AND ISOLATED STRONG CONVECTION FOUND WITHIN 120 NM W OF 
THE TROUGH FROM 07N TO 11N AND WITHIN 120 NM E OF THE TROUGH 
FROM 11N TO 12N. THIS TROUGH LIES IN AN AREA OF UPPER LEVEL 
DIFFLUENCE BETWEEN AN ANTICYCLONE CENTERED NEAR 11N115W AND A 
40-50 KT SOUTHWESTERLY UPPER JET TO ITS NW FROM 10N137W TO 
24N130W. A 1010 MB SURFACE LOW CAN BE FOUND IN CONJUNCTION WITH 
THE REAR RIGHT QUADRANT OF THIS UPPER JET NEAR 07N135W. ONLY 
ISOLATED MODERATE CONVECTION IS FOUND IN ASSOCIATION WITH THIS 
SURFACE LOW...WITH SATELLITE TOTAL PRECIPITABLE WATER IMAGERY 
SHOWING THE BULK OF THE MOISTURE POOLED TO THE EAST OF THIS LOW 
NEAR THE AFOREMENTIONED SURFACE TROUGH. A SECOND SURFACE LOW 
LIES NEAR 10N104W. THIS 1010 MB LOW HAS SCATTERED MODERATE 
CONVECTION WITHIN 180 NM OF ITS E SEMICIRCLE AND 120 NM OF ITS W 
QUADRANT. THIS SURFACE LOW LIES UNDER AN UPPER RIDGE AXIS 
STEMMING FROM AN ANTICYCLONE CENTERED NEAR 10N88W AND EXTENDING 
W TO 07N100W AND TO 14N122W. THIS UPPER RIDGE WILL CONTRACT E AS 
THE TROUGHING ASSOCIATED WITH THE UPPER LOW OVER N WATERS PASSES 
E TOWARD THE ANTICYCLONE. IN ADDITION...NORTHERLY WINDS ON THE 
WESTERN SIDE OF THE ANTICYCLONE ARE EXPECTED TO INCREASE THE 
NEXT FEW DAYS...LIMITING CONVECTION OVER FAR E WATERS. CURRENTLY 
SCATTERED MODERATE CONVECTION IS FOUND HERE WITHIN 120 NM S OF 
THE ITCZ AXIS W OF 78W...ALONG THE COLOMBIAN COAST.

1035 MB HIGH PRES OVER THE NORTHERN U.S. ROCKY MOUNTAINS WILL 
SETTLE SOUTH TO THE RIO GRANDE VALLEY FRI AND THEN PUSH RAPIDLY 
EASTWARD OVER THE WEEKEND. THE PRESSURE GRADIENT BETWEEN THIS 
HIGH AND AND TROUGHING IN THE VICINITY OF THE GULF OF CALIFORNIA 
HAS STRENGTHENED THE NW TO N WINDS IN THE NORTHERN GULF OF 
CALIFORNIA TO THE 20 TO 25 KT RANGE ACCORDING TO THE 0410 ASCAT 
PASS. THESE WINDS ARE EXPECTED TO DIMINISH BELOW 20 KT BY SAT 
AFTERNOON AS THE HIGH PRESSURE SYSTEM MOVES AWAY.  

GAP WINDS...
GULF OF TEHUANTEPEC...THE 0406 UTC ASCAT PASS REVEALED NORTH 
WINDS FUNNELING THROUGH THE GULF OF TEHUANTEPEC IN THE 25 TO 30 
KT RANGE. AS THE AFOREMENTIONED HIGH PRESSURE OVER THE U.S. 
SINKS SOUTHWARD TOWARD THE RIO GRANDE VALLEY...EXPECT WINDS TO 
INCREASE TO GALE FORCE IN THE GULF OF TEHUANTEPEC ON SAT 
MORNING. HOWEVER...THIS EVENT SHOULD BE BRIEF CONSIDERING THE 
SPEED AT WHICH THE HIGH PRES SYSTEM IS EXPECTED TO MOVE EAST. 
GALE FORCE WINDS ARE EXPECTED TO DIMINISH SUN MORNING.

GULF OF PAPAGAYO...EXPECT ELY WINDS AT OR NEAR 20 KT TO PULSE UP 
AND DOWN THROUGH THE GULF OF PAPAGAYO AND THEN DOWNSTREAM TO 
NEAR 89W DURING THE NEXT FEW DAYS. THESE WINDS WILL BE STRONGEST 
IN THE MORNING HOURS WITH THE AID OF DRAINAGE FLOW. 

$$
SCHAUER