000
AXPZ20 KNHC 202126
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU DEC 20 2007

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.
 
...ITCZ...

INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 6N77W 8N100W 
9N118W 8N140W. SCATTERED MODERATE CONVECTION WITHIN 75 NM OF 
AXIS BETWEEN 103W-124W.

...DISCUSSION...

E OF 120W...
A BROAD BUT FLAT MID-LEVEL RIDGE EXTENDS ACROSS MUCH OF CENTRAL 
AMERICA...SOUTHERN MEXICO...AND THE ADJACENT PACIFIC WATERS 
ALONG 15N E OF 120W...PRODUCING FAIRLY STRONG SUBSIDENCE OVER 
THE REGION. THE ITCZ IS ONLY SLIGHTLY PERTURBED OVER THE AREA 
BUT THE ASSOCIATED LOW-LEVEL CONVERGENCE IS RATHER WEAK...HENCE 
THE AXIS IS NOT PARTICULARLY WELL-DEFINED. FARTHER N...WESTERLY 
MID-LATITUDE FLOW EXTENDS FROM W OF BAJA CALIFORNIA ACROSS 
NORTHERN MEXICO. A SHORTWAVE TROUGH IS NOTED WITHIN THE FLOW 
MOVING OFF THE TEXAS GULF COAST AND IS LEAVING A WEAK SHORTWAVE 
RIDGE IN ITS WAKE ACROSS THE RIO GRANDE VALLEY. ANOTHER TROUGH 
LIES W OF 120W AND THE ASSOCIATED UPPER DIFFLUENCE IS PRODUCING 
MID/HIGH LEVEL CLOUDINESS WHICH IS JUST BEGINNING TO APPROACH 
THE BAJA PENINSULA. THE SUBTROPICAL JET RUNS FROM THE BASE OF 
THE TROUGH ACROSS SOUTHERN BAJA INTO NORTHERN MEXICO WHERE JET 
SPEEDS ACCELERATE TO 70-100 KT HEADING INTO THE GULF OF MEXICO.

W OF 120W...
THE AFOREMENTIONED UPPER TROUGH DESCRIBED ABOVE EXTENDS FROM 
30N120W TO 19N130W WITH UPPER RIDGING BUILDING TO ITS WEST NEAR 
140W. ANOTHER SHORTWAVE TROUGH IS PLUNGING SWD TOWARDS 30N 
WITHIN THE BASE OF A MUCH LARGER TROUGH LOCATED ACROSS THE 
SIERRA NEVADAS OF THE WESTERN UNITED STATES. A COLD FRONT IS 
ALSO PLUNGING S OFF THE CALIFORNIA COAST AND IS JUST BEGINNING 
TO CROSS 30NW OF 125W. HIGH PRES WILL BUILD IN BEHIND THE FRONT 
AND WILL INCREASE NORTHERLY WINDS OFF THE COAST OF BAJA 
CALIFORNIA AS WELL AS THROUGH THE GULF OF CALIFORNIA FRI THROUGH 
SUN.

$$
BERG