000
AXPZ20 KNHC 090924
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN DEC 09 2007

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 
0845 UTC.
 
...ITCZ...
INTERTROPICAL CONVERGENCE ZONE AXIS ALONG 6N77W 7N87W 6N100W 
9N127W 8N140W. ISOLATED MODERATE CONVECTION NEAR 7N78W 7N80W AND 
7N83W.  

OTHER MODERATE CONVECTION WITHIN 60 NM OF A LINE FROM 20N115W TO 
14N119W.

...DISCUSSION...

LARGE POOL OF COLD AIR ALOFT CENTERED JUST OFF THE SRN CA COAST 
CONTINUES MOVING SWD TONIGHT AND LOWERING MID LEVEL HEIGHTS N OF 
20N BETWEEN 105W AND 130W. AN OLD MID LEVEL RIDGE ALONG 140W 
EXTENDS N OF 50N AND IS BLOCKING THE WESTERLIES OVER THE MID 
PACIFIC. ON THE SURFACE TONIGHT A DISSIPATING COLD FRONT 
EXTENDED FROM LOWER BAJA TO 20N130W. THE PACIFIC HIGH CENTERED N 
OF THE AREA ALONG 136W EXTENDS S AND SE OVER THE REGION TO 
15N110W. A TIGHT PRESSURE GRADIENT N OF 30N BETWEEN LOW PRES 
ALONG THE SRN CA COAST AND THE PACIFIC HIGH IS PRODUCING GALE 
CONDITIONS. THE WINDS DECREASE S OF 30N TO 20 TO 25 KT BUT NLY 
SWELL TO 14 FT IS WORKING IT'S WAY S BETWEEN 118W AND 128W. GAP 
WINDS ARE MOSTLY LIGHT EXCEPT FOR PAPAGAYO WHERE SSMI AND ASCT 
MICROWAVE IMAGERY SHOW 20 TO 25 KT. CROSS EQUATORIAL SE WINDS S 
OF 5N W OF 110W OF 20 KT ALSO REPORTED BY SSMI AND QUIKSCAT 
IMAGERY. 

LATER DAY 1 THE POOL OF COLD AIR ALOFT WILL CONTINUE TO SINK SWD 
ALONG 120W WHILE THE BLOCKING RIDGE ALONG 140W REMAINS IN PLACE. 
ON THE SURFACE LATER DAY 1 THE GFS MODEL SHOWS WEAK LOW PRES 
BENEATH THE UPPER POOL OF COLD AIR FORMING NEAR 29N116W THUS THE 
PRES GRADIENT WILL REMAIN TIGHT N OF 25N BETWEEN 120W AND 128W 
RESULTING IN NLY WINDS TO 25 KT AND NLY SWELL TO 15 FT. LITTLE 
CHANGE TO GAP WINDS WITH AN AREA W OF PAPAGAYO CONTINUING TO GET 
20 TO 25 KT FROM THE NE. CROSS EQUATORIAL WINDS MOSTLY 10 TO 15 
KT.

FOR DAY 2 THE STRONG UPPER TROUGH ASSOCIATED WITH THE POOL OF 
COLD AIR IS FORECAST TO CLOSE OFF WITH A CENTER NEAR 30N115W. 
GFS MODEL SHOWS THE BLOCKING RIDGE ALONG 140W DRIFTING E AND 
WEAKENING AS ANOTHER STRONG MID LEVEL TROUGH APPROACHES FROM THE 
NW. ON THE SURFACE DAY 2 THE PACIFIC RIDGE WILL WEAKEN SOME IN 
RESPONSE TO THE WEAKENING RIDGE ALOFT. THE LOW PRES CENTER OFF 
THE NRN BAJA COAST WILL MOVE INLAND BUT WINDS ALONG THE BAJA 
COAST WILL REMAIN W TO NW 20 TO 25 KT WITH NW SWELL 9 TO 13 FT. 
LITTLE CHANGE TO GAP WINDS. CROSS EQUATORIAL SLY WINDS MOSTLY 10 
TO 15 KT.

$$
RRG