000
AXPZ20 KNHC 180925
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI JAN 18 2008

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 
0900 UTC.
 
...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N78W 4N82W 4N90W 9N117W 6N132W 
6N140W. NO SIGNIFICANT CONVECTION.

...DISCUSSION...

N OF 20N...
A LARGE LONGWAVE TROUGH REMAINS PLANTED ACROSS MUCH OF NORTH 
AMERICA WITH A RELATIVELY NARROW BUT BLOCKING UPPER LEVEL 
ANTICYCLONE OFF THE COASTS OF OREGON AND NORTHERN CALIFORNIA. A 
SHARP MID/UPPER LEVEL SHORTWAVE IS APPROACHING THE BASE OF THE 
TROUGH AND CURRENTLY EXTENDS FROM SE NEW MEXICO SW ACROSS NW 
MEXICO AND BAJA CALIFORNIA TO NEAR 25N120W 30N128W. WHAT MAY BE 
AN ASSOCIATED COLD FRONT APPEARS TO HAVE PUSHED SWD ACROSS THE 
BAJA PENINSULA NOW FROM NEAR LOS MOCHIS TO LA PAZ THEN TO 
22N118W WITH NOTICEABLY CLEARER SKIES EXTENDING N TOWARDS 
CALIFORNIA. A FEW CLOUDS REMAIN NEAR AND S OF THE 
BOUNDARY...INCLUDING NEAR CABO SAN LUCAS...BUT THIS TOO SHOULD 
CLEAR AS THE FRONT PUSHES S TODAY. THE STRONG NWLY WINDS OVER 
THE GULF OF CALIFORNIA BEHIND THE FRONT HAVE DIMINISHED TO 20-25 
KT AND SHOULD DIMINISH SLIGHTLY THROUGH THE DAY. FARTHER W...A 
WEAKENED UPPER RIDGE LIES ALONG 128W BUT IS BEING REPLACED BY A 
NEGATIVELY TITLED TROUGH EXTENDING FROM 25N133W NW PAST 20N138W.

S OF 20N...
THE UPPER FLOW OVER THE TROPICS HAS CONTINUED TO BECOME 
INCREASINGLY ZONAL WITH ONLY THE SLIGHTEST HINT OF A LEFTOVER 
TROUGH ALONG 105W. OTHERWISE...STRONG UPPER LEVEL WESTERLIES LIE 
W OF 105W WHERE MAXIMUM WIND SPEEDS ARE NEAR 85 KT. WIDESPREAD 
BUT MOSTLY BROKEN HIGH CLOUDS ARE BEING ADVECTED EWD BY THIS 
SUBTROPICAL JET LYING N OF 10N W OF 102W. E OF THE UPPER 
TROUGH...THE FLOW IS MAINLY SOUTHWESTERLY AND EXCEPTIONALLY DRY 
ABOVE THE BOUNDARY LAYER DUE TO STRONG RIDGING. THERE IS A 
NOTEWORTHY LOW-LEVEL MOISTURE POOL S OF 7N E OF 94W BUT THE 
STRONG SUBSIDENCE IS CAPPING ANY POSSIBLE DEEP CONVECTION.

A GALE WARNING IS IN EFFECT FOR THE GULF OF TEHUANTEPEC DUE TO A 
NORTHERLY SURGE WHICH WILL ARRIVE IN ABOUT 42-48 HOURS (SAT 
NIGHT). WINDS ARE EXPECTED TO REACH UP TO 45 KT AND WARNING 
CONDITIONS WILL LIKELY CONTINUE UNTIL MON MORNING.

$$
BERG