000
AXPZ20 KNHC 050944
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 05 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 
0600 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS ANALYZED ALONG 06N77W TO 
07N85W TO 06N95W TO 09N120W TO 05N140W. SCATTERED MODERATE 
CONVECTION LIES WITHIN 90 NM EITHER SIDE OF AXIS W OF 130W.

...DISCUSSION...
AN AMPLIFIED UPPER PATTERN IS IN PLACE OVER THE FORECAST AREA N 
OF 20N...WITH AN UPPER LOW NEAR 29N125W PASSING THROUGH THE MEAN 
UPPER RIDGE AXIS AND MOVING INTO THE SW EDGE OF THE MEAN BROAD 
TROUGH OVER NORTH AMERICA WITHIN THE NEXT 24 HOURS. 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 OR LESS THE NEXT FEW 
DAYS. TO THE W OF THIS UPPER RIDGE AXIS CENTERED OVER THE 
CENTRAL N PACIFIC LIES ANOTHER MEAN UPPER TROUGH. AN UPPER LOW 
IS CURRENTLY MOVING NORTHEASTWARD ON THE LEADING EDGE OF THIS 
BROAD TROUGH AND CARRYING AN ASSOCIATED COLD FRONT SE TOWARD THE 
NW FORECAST WATERS. SOUTHERLY WINDS IN ADVANCE OF THIS FRONT ARE 
ALREADY BEGINNING TO APPROACH 20 KT OVER THE NW WATERS. NW SWELL 
IN THE 8 TO 12 FT RANGE WILL MOVE SE INTO THE AREA AHEAD OF THE 
FRONT. THE FRONT IS EXPECTED TO WEAKEN BY SUN NIGHT AND BECOME 
MORE POSITIVELY TILTED OVER N WATERS.

S OF 20N...TWO LOW PRES SYSTEMS ARE EMBEDDED WITHIN THE ITCZ. 
THE 1010 MB SURFACE LOW NEAR 08N128W IS THE MOST CONVECTIVELY 
ACTIVE...WITH SCATTERED MODERATE CONVECTION FOUND WITHIN 180 NM 
N SEMICIRCLE OF THE LOW. THIS LOW LIES IN AN AREA OF UPPER LEVEL 
DIFFLUENCE IN THE REAR RIGHT QUADRANT OF A SOUTHWESTERLY UPPER 
JET FROM 14N135W TO 23N120W. A SECOND SURFACE LOW LIES NEAR 
09N108W. THIS 1010 MB LOW HAS ISOLATED MODERATE CONVECTION 
WITHIN 180 NM OF ITS E SEMICIRCLE. THIS SURFACE LOW LIES NEAR 
AND UPPER ANTICYCLONE CENTERED NEAR 10N97W AND EXTENDS NW TO 
15N130W. THIS UPPER RIDGE WILL CONTRACT SE 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 HAVE INCREASED...LIMITING CONVECTION OVER FAR 
E WATERS. 

1028 MB HIGH PRES OVER THE NORTHERN RIO GRANDE VALLEY FRI 
WILL PUSH RAPIDLY EASTWARD OVER THE WEEKEND. THE PRESSURE 
GRADIENT BETWEEN THIS HIGH 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...BUT THEY 
ARE EXPECTED TO DIMINISH BELOW 20 KT THIS MORNING. HOWEVER... 
WINDS WILL ONCE AGAIN EXCEED 20 KT BY SUN MORNING IN ADVANCE OF 
A NEW COLD FRONT DIVING THROUGH THE GREAT BASIN.

GAP WINDS...
GULF OF TEHUANTEPEC...AS THE AFOREMENTIONED HIGH PRESSURE OVER 
THE TEXAS EDGES EASTWARD INTO THE NW GULF OF MEXICO...EXPECT 
WINDS TO INCREASE TO GALE FORCE IN THE GULF OF TEHUANTEPEC LATER 
THIS 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 EARLY SUN 
MORNING.

GULF OF PAPAGAYO...EXPECT ELY WINDS 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...20 TO 25 KT...IN 
THE MORNING HOURS WITH THE AID OF DRAINAGE FLOW. 

$$
SCHAUER