000
AXPZ20 KNHC 051537
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 05 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 
1500 UTC.

...ITCZ...

AXIS ANALYZED ALONG 04N77W TO 10N108W TO 06N116W TO 11N128W TO 
06N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION WAS 
NOTED WITHIN 90 NM OF THE AXIS E OF 83W...WITHIN 60 NM OF THE 
AXIS BETWEEN 104W AND 106W...WITHIN 120 NM S OF THE AXIS BETWEEN 
111W AND 115W...AND WITHIN 150 NM OF THE AXIS W OF 124W.

...DISCUSSION...

AN AMPLIFIED UPPER PATTERN IS IN PLACE OVER THE FORECAST AREA N 
OF 18N...WITH A SHALLOW SHORTWAVE UPPER TROUGH FROM NEAR 30N116W 
TO 25N119W FLATTENING OUT AS IT MOVES TO THE E INTO NORTHERN 
MEXICO. THE PASSAGE OF THIS SHORTWAVE ENERGY THROUGH THE UPPER 
RIDGE WILL HELP KEEP BROAD SURFACE RIDGING ON THE WEAK SIDE OVER 
THE NORTH WATERS...CONTAINING THE COVERAGE OF 20 KT EASTERLY 
TRADES GENERALLY FROM 11N TO 18N BETWEEN 120W AND 135W...WITH 
LESS THAN 20 KT ELSEWHERE. TO THE W-NW OF THE DISCUSSION AREA A 
LONGWAVE UPPER TROUGH IS PRESENT WITH AN EMBEDDED UPPER LOW NEAR 
35N145W MOVING NORTHEASTWARD ON THE LEADING EDGE OF THE TROUGH 
AXIS. THIS FEATURE IS CARRYING AN ASSOCIATED SURFACE COLD FRONT 
TO THE E-SE TOWARD THE NW FORECAST WATERS. SOUTHERLY WINDS IN 
ADVANCE OF THIS FRONT ARE ALREADY IN THE 20 TO 25 KT RANGE AS 
INDICATED BY AN EARLIER 0712 UTC ASCAT PASS. THIS FRONT AND 
ASSOCIATED WINDS WILL CONTINUE TO PROGRESS TO THE E...SKIRTING 
THE FAR N PORTION OF OUR AREA DURING THE NEXT 48 HOURS. IN 
ADDITION...NW SWELL IN THE 8 TO 13 FT RANGE WILL PROPAGATE TO 
THE SE INTO THE AREA AHEAD OF THE FRONT.

S OF 18N...THREE WEAK SURFACE LOW PRES SYSTEMS ARE EMBEDDED 
WITHIN THE ITCZ. A 1009 MB LOW NEAR 09N129W HAS SCATTERED 
MODERATE AND ISOLATED STRONG CONVECTION WITHIN 150 NM OF THE LOW 
IN THE NE QUADRANT. THIS LOW LIES IN AN AREA OF UPPER LEVEL 
DIFFLUENCE IN THE RIGHT REAR QUADRANT OF A SOUTHWESTERLY UPPER 
JET FROM 26N114W TO 14N133W. ANOTHER 1009 MB LOW IS POSITIONED 
NEAR 09N109W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION 
EXISTS WITHIN 120 NM OF THE LOW IN THE NE QUADRANT. TO THE E OF 
THIS LOW THERE IS AN UPPER ANTICYCLONE CENTERED AT 11N96W WITH 
AN UPPER RIDGE EXTENDING TO THE NW NEAR 17N129W. THIS UPPER 
RIDGE WILL CONTRACT TO THE SE AS THE UPPER TROUGH JUST TO THE 
N-NW MOVES TO THE E-SE TOWARD THE ANTICYCLONE. A 1008 MB LOW IS 
CENTERED NEAR 06N139W AND WILL SOON BE EXITING THE DISCUSSION 
AREA AS IT CONTINUES TO MOVE TO THE W AROUND 10 KT. SCATTERED 
MODERATE AND ISOLATED STRONG CONVECTION CAN BE FOUND WITHIN 120 
NM IN THE N SEMICIRCLE AND WITHIN 210 NM IN THE SW QUADRANT OF 
THIS LOW.

THE PRES GRADIENT IN THE VICINITY OF THE GULF OF CALIFORNIA HAS 
WEAKENED EARLY THIS MORNING...AND AS A RESULT NORTHERLY WINDS 
HAVE DIMINISHED TO LESS THAN 20 KT. WINDS WILL VEER TO THE SW 
AND INCREASE TO 20 TO 25 KT LATE TONIGHT N OF 29N IN ADVANCE OF 
A COLD FRONT DIVING DOWN THROUGH THE U.S. GREAT BASIN.

GAP WINDS...
GULF OF TEHUANTEPEC...STRONG HIGH PRES CONTINUES TO BUILD IN 
OVER THE SW GULF OF MEXICO AND BAY OF CAMPECHE. AS A RESULT 
NORTHERLY WINDS ARE BEING FUNNELED ACROSS THE ISTHMUS OF 
TEHUANTEPEC AND OVER THE GULF OF TEHUANTEPEC...WITH GALE FORCE 
CONDITIONS NOW OCCURRING THERE. THE HIGH TO THE N WILL WEAKEN
AND QUICKLY SHIFT TO THE NE OVER THE SE U.S. STATES TONIGHT... 
AND WINDS WILL DIMINISH TO BELOW GALE FORCE AROUND 06 UTC SUN... 
THEN WILL FURTHER DIMINISH TO LESS THAN 20 KT BY SUN EVENING.

GULF OF PAPAGAYO...EASTERLY WINDS WILL CONTINUE TO PULSE UP AND 
DOWN THROUGH THE GULF OF PAPAGAYO AND DOWNSTREAM WATERS TO 90W 
DURING THE NEXT FEW DAYS. A SHIP WITH CALL SIGN 3FSA4 NEAR 
11N89W REPORTED 20 KT NE WINDS AT 1500 UTC. THESE WINDS WILL BE 
STRONGEST...20 TO 25 KT...DURING THE MORNING HOURS WITH THE AID 
OF DRAINAGE FLOW. 

$$
LEWITSKY