000
AXPZ20 KNHC 301002
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT DEC 30 2006

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0930 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 4N78W 5N90W 8N100W 7.5N110W 6N120W
6N130W 6N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN 113W-117W. SCATTERED
MODERATE CONVECTION IS WITHIN 30 NM OF AXIS BETWEEN 131W-133W.

...DISCUSSION...

EAST OF 120W...

THE AREA IS DOMINATED BY BROAD MID TO UPPER LEVEL TROUGHING.
HOWEVER THE TROUGHING IS FLATTENING OUT WITH TIME AS SEEN
IN THE FLOW PATTERN BECOMING MORE ZONAL NORTH OF ABOUT 16N. 
SATELLITE WATER VAPOR IMAGERY SHOWS AMPLE STRONG SUBSIDENCE AND 
ASSOCIATED DRY COVERING JUST ABOUT THIS ENTIRE AREA EXCEPT FOR 
PORTION FROM 9N-17N EAST OF 103.5W WHERE MID AND UPPER LEVEL 
MOISTURE IN THE FORM OF MOSTLY CIRRUS CLOUDINESS ARE STREAMING
TOWARDS SOUTHEASTERN MEXICO. MID/UPPER LEVEL RIDGING WILL REPLACE
THE TROUGH THROUGH SUNDAY...THEN A SHORTWAVE TROUGH IS FORECAST
TO DROP SOUTHEASTWARD THROUGH THE NORTHEAST PART MON AND TUE
THEN NUDGE FURTHER SOUTHEAST DURING THE MIDDLE TO LATTER PART
OF THE UPCOMING WEEK. AT THE SURFACE...A SURFACE TROUGH EXTENDS
FROM JUST WEST OF NORTHERN BAJA CALIFORNIA NORTHWESTWARD TO 
NORTH OF 32N AS IT PARALLELS THE CALIFORNIA COASTLINE. A WEAK 
1009 MB LOW MOVING WESTWARD 10-15 KT WITH NO DEEP CONVECTION
IS ANALYZED ON THE ITCZ AXIS NEAR 8N104W. HIGH PRESSURE EXISTS 
NORTH OF 16N BETWEEN 110W-120W WITH GENERALLY LIGHT N-NE FLOW 
BEING OBSERVED HERE. THE FLOW NEAR THE BAJA CALIFORNIA WEST 
COAST MAY INCREASE SOME WED AND THU AS THE SHORTWAVE TROUGH
MOVES OVER THE AREA. A COLD FRONT PRESENTLY ENTERING THE
WESTERN GULF OF MEXICO WILL BE FOLLOWED BY HIGH PRESSURE
BUILDING SOUTHWARD INTO SOUTHEASTERN MEXICO BEGINNING SUN.
GFS WIND FIELDS ARE IMPLYING THAT NLY WINDS WILL INCREASE 
OVER THE GULF OF TEHUANTEPEC BEGINNING SUN NIGHT AND LASTING
THROUGH WED AFTERNOON. THESE WINDS ARE FORECAST TO REMAIN AT JUST
BELOW GALE FORCE.

WEST OF 120W...

BROAD MID AND UPPER RIDGING COVERS THIS PORTION OF THE REGION 
WITH A MID/UPPER LEVEL ANTICYCLONIC CIRCULATION LOCATED OVER THE 
ITCZ NEAR 7N132W. SURFACE HIGH PRESSURE IS PRESENT NORTH OF 16N. 
DEEP LAYERED TROUGH IS SHARPENING WITH TIME TO THE WEST OF THE 
REGION ALONG 148W. NWP MODELS SUGGEST THAT THIS TROUGH WILL 
ENTER THE NORTHWEST PART SUN. ON MON AND TUE...THE TROUGH SPLITS 
WITH THE SOUTHERN TIER BECOMING A CUT-OFF UPPER LEVEL LOW WEST 
OF THE REGION NEAR 15N144W...WHILE THE REMAINDER OF THE TROUGH 
BEGINS TO TRANSLATE MORE INTO A SHEAR AXIS NORTHEAST TO 
SOUTHWEST ACROSS THE AREA INTO WED OF NEXT WEEK. THE CUT-OFF LOW 
BEGINS TO LIFT NORTHEASTWARD TOWARDS THE END OF THE WEEK AS IT 
GETS A BOOST FROM A LARGE MID/UPPER LEVEL TROUGH TO THE 
NORTHWEST OF THE REGION. NWP MODELS FORECAST THE SHEAR AXIS 
BEING REPLACED BY HIGH PRESSURE ALSO TOWARDS THE END OF THE 
UPCOMING WEEK. EXPECT MODERATE NORTHEAST TRADES CURRENTLY FOUND 
FROM 8N-26N TO WEAKEN BEGINNING TUE AS THE SURFACE HIGH PRESSURE 
WEAKENS IN RESPONSE TO AN APPROACHING WEAK FRONT ASSOCIATED WITH 
THE TROUGH STATED ABOVE. MAIN PROBLEM...HOWEVER...WILL BE LARGE 
PREDOMINATELY NW SWELLS THAT WILL PLAGUE THE NORTHWEST SECTOR 
BEGINNING ON WED AND CONTIUNING INTO FRI.

$$
AGUIRRE