000
AXPZ20 KNHC 061617
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN DEC 06 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...
THE INTERTROPICAL CONVERGENCE ZONE...AXIS ANALYZED ALONG 05N76W 
TO 07.5N85W TO 07N99W TO 11N109W...THEN RESUMES FROM 11N114W TO 
08N122W TO 08N142W. ISOLATED TO SCATTERED MODERATE CONVECTION 
WAS WITHIN 120 NM S OF AXIS E OF 83W. SCATTERED MODERATE TO 
STRONG CONVECTION WAS WITHIN 60 NM N AND 120 NM S OF AXIS 
BETWEEN 97W AND 109W. SCATTERED TO NUMEROUS MODERATE TO STRONG 
CONVECTION WAS WITHIN 60 NM N AND 180 NM S OF AXIS BETWEEN 116W 
AND 129W.

...DISCUSSION...
THE AMPLIFIED UPPER PATTERN THAT HAD BEEN IN PLACE THE LAST FEW 
DAYS OVER THE FORECAST AREA N OF 20N HAS BEGUN TO BREAK DOWN AND 
IS FORECAST BY GLOBAL MODELS TO PRODUCE A VERY ACTIVE AND 
ENERGETIC UPPER LEVEL SRN STREAM FLOW INTO CALIFORNIA...THE N 
HALF OF MEXICO...AND THE DESERT SW OF THE U.S. OVER THE NEXT 
SEVERAL DAYS. CURRENTLY...AN UPPER LOW REMAINS NEARLY STATIONARY 
ACROSS THE NW WITH A SIGNIFICANT S/W TROUGH MOVING THROUGH THE 
BASE OF THIS BROAD CIRCULATION...NEGATIVELY TILTED FROM THE LOW 
SE THROUGH N AND CENTRAL TEXAS. AN UPPER LEVEL HIGH WAS LOCATED 
OVER THE TROPICAL EPAC OFF OF CENTRAL AMERICA NEAR 
11N92W...RIDGING WWD ALONG 11-12N TO 132W. A MID-UPPER LEVEL 
TROUGH WAS ENTERING W PORTIONS OF THE AREA...EXTENDING FROM A 
PROGRESSIVE S/W NEAR 33N125W...SW TO 23N140W...THEN CONTINUED AS 
A VERY SHARP AND NEARLY STATIONARY TROUGH TO 12N150W CONTINUING 
WSW INTO THE TROPICAL CENTRAL PACIFIC. STRONG UPPER LEVEL SW TO 
W FLOW WAS FOUND SE AND E OF THE THIS TROUGH AND ACROSS THE 
UPPER RIDGE. 

THE TROUGH ENTERING W PORTIONS OF THE AREA WAS SUPPORTING A COLD 
FRONT EXTENDING FROM 30N137.5W TO 27.5N140W AND BEYOND...AND WAS 
THE LEADING EDGE OF YET ANOTHER PULSE OF LARGE NW SWELL. THE S/W 
ENERGY ASSOCIATED WITH THIS TROUGH WILL PASS ACROSS THE MEAN 
RIDGE AXIS TODAY AND INTO THE MEAN TROUGH REORGANIZING OVER WRN 
NORTH AMERICA. THE PASSAGE OF THIS SHORTWAVE ENERGY ACROSS THE 
UPPER RIDGE WILL HELP WEAKEN ANY DEEP LAYER RIDGING AND KEEP THE 
SURFACE HIGH WEAK ACROSS NORTH WATERS...THUS REDUCING THE AREA 
OF NE TO ELY TRADE WINDS TO 20 KT DURING THE NEXT FEW DAYS. THE 
COLD FRONT WILL MOVE E RELATIVELY QUICKLY AND ACROSS SRN 
CALIFORNIA AND APPROACH THE NRN BAJA PENINSULA MONDAY 
NIGHT....ACCOMPANIED BY NWLY SWELL YIELDING SEAS 9 TO 11 FT 
ACROSS NE PORTIONS. THE REORGANIZING TROUGH ACROSS THE WRN U.S. 
IS FORECAST TO PRODUCE A DEEP LAYERED LOW...WITH A SURFACE 
REFLECTION DEVELOPING ACROSS SRN NEVADA. THIS SHOULD PRODUCE A 
TIGHT PRESSURE GRADIENT ACROSS NE PORTIONS OF THE AREA INTO THE 
NRN GULF OF CALIFORNIA...AND A BRIEF PERIOD OF WINDS TO 30 KT 
INTO THE GULF MONDAY NIGHT THROUGH TUE MORNING. 

MEANWHILE...A NEW FRONT WILL APPROACH NW WATERS BY EARLY TUE AND 
BRING A NEW PULSE OF NW SWELL WITH SEAS RISING TO 18 FT BEHIND 
THE FRONT.

S OF 20N...TWO LOW PRES SYSTEMS ARE EMBEDDED WITHIN THE ITCZ. 
THE 1012 MB SURFACE LOW NEAR 08N131W HAS SCATTERED MODERATE 
CONVECTION FOUND WITHIN 150 NM W SEMICIRCLE OF THE LOW. THIS LOW 
IS MOVING INTO A REGION OF STRONGER UPPER WINDS FROM THE SW THAT 
WILL LIMIT ANY FURTHER DEVELOPMENT OF THE LOW. A SECOND SURFACE 
LOW LIES NEAR 10N112W. THIS 1009 MB LOW HAS SCATTERED MODERATE 
WITH ISOLATED STRONG CONVECTION WITHIN 150 NM OF THE CENTER. 
THIS LOW LIES UNDER THE RIDGE AXIS...WHICH CONTINUES TO 
VENTILATE ITCZ CONVECTION VERY WELL TO THE E OF THE LOW TO 120W. 
THIS SYSTEM IS MORE LIKELY TO SURVIVE THE NEXT FEW DAYS AS IT 
REMAINS IN A REGION OF UPPER LEVEL DIFFLUENCE ASSOCIATED WITH 
THIS STATIONARY UPPER RIDGE AXIS. EXPECT SHOWERS AND 
THUNDERSTORMS TO CONTINUE IN THIS TROPICAL REGION E OF THE LOW 
FOR THE NEXT DAY OR TWO AS THE UPPER JET REMAINS RELATIVELY 
STATIONARY THERE.

GAP WINDS...
GULF OF TEHUANTEPEC...GALE FORCE NORTHERLY WINDS ARE ASSUMED TO 
HAVE DIMINISHED THIS MORNING AS THE HIGH PRES OVER THE GULF OF 
MEXICO HAS SHIFTED NORTHEASTWARD AWAY FROM THE AREA...LEAVING A 
PLUME OF 20-25 KT WINDS...WITH A SMALL AREA OF 30 KT WINDS JUST 
DOWNWIND OF THE GULF.  

GULF OF PAPAGAYO...EXPECT ELY WINDS TO PULSE UP AND DOWN THROUGH 
THE GULF OF PAPAGAYO AND THEN DOWNSTREAM TO NEAR 91W DURING THE 
NEXT FEW DAYS. THESE WINDS WILL BE STRONGEST...20 TO 25 KT...IN 
THE MORNING HOURS WITH THE AID OF DRAINAGE FLOW. 

$$
STRIPLING