000
AXPZ20 KNHC 311534
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU JAN 31 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1515 UTC.
 
...ITCZ...

ITCZ AXIS IS CENTERED ALONG 2N78W 5N86W 4N110W 9N140W. NO 
SIGNIFICANT CONVECTION.

...DISCUSSION...

E OF 110W...
A DEEP LONGWAVE TROUGH IS CENTERED OVER THE MIDDLE PART OF THE 
UNITED STATES AND REACHES S OVER NORTHERN MEXICO. A STRONG 
SHORTWAVE TROUGH IS EMBEDDED WITHIN THE LARGER-SCALE TROUGH OVER 
NW TEXAS AND A TIGHT GEOPOTENTIAL GRADIENT IS PRODUCING A 
SIGNIFICANT 90-100 KT JET WHICH PLUNGES S ACROSS THE FOUR 
CORNERS REGION THEN SPREADS NE ACROSS THE MISSISSIPPI AND OHIO 
VALLEYS. CONFLUENCE INTO THE BASE OF THE TROUGH IS PRODUCING 
SINKING AIR OVER NORTHERN MEXICO WHERE SKIES ARE MOSTLY CLEAR. 
FARTHER SE...A CUT-OFF UPPER TROUGH EXTENDS FROM THE ISTHMUS OF 
TEHUANTEPEC SWD TO 4N96W AND IS COLLOCATED WITH A MID-LEVEL 
RIDGE ALONG 17N. AS SUCH...SUBSIDENCE IS ALSO THE RULE OVER 
CENTRAL AMERICA AND THE ADJACENT PACIFIC WATERS...BECOMING 
STRONGEST E OF THE TROUGH AXIS. SURFACE WINDS...INCLUDING THOSE 
DOWNSTREAM OF THE GAPS...ARE GENERALLY LIGHT ALTHOUGH WINDS 
CONTINUE TO PULSE TO 20 KT OVER THE GULF OF PAPAGAYO.

A GALE WARNING IS IN EFFECT FOR THE GULF OF TEHUANTEPEC FOR 
WINDS INCREASING TO 30-40 KT BY FRI AFTERNOON. A COLD FRONT 
MOVING OFF THE TEXAS COAST WILL REACH SOUTHERN MEXICO BY FRI AND 
WILL PROVIDE A QUICK PULSE OF NORTHERLY WINDS OVER TEHUANTEPEC. 
GALE CONDITIONS ARE ONLY EXPECTED TO LAST FOR 18 HRS OR 
SO...UNTIL SAT MORNING. CONFIDENCE IS HIGH THAT THE EVENT WILL 
OCCUR BUT TIMING/STRENGTH IS A LITTLE UNCERTAIN WITH THE NAM 
ABOUT 6 HRS EARLIER AND UP TO 15 KT STRONGER THAN THE GFS. THE 
FORECAST TAKES A BLEND OF THE MIXED-LAYER WINDS FROM BOTH MODELS.

W OF 110W...
UPPER LEVEL SPLIT FLOW IS ENTRENCHED OVER THE WESTERN PART OF 
THE AREA WITH UPPER LEVEL RIDGING N OF 17N ALONG 130W...AND AN 
UPPER TROUGH S OF 17N ALONG 134W. UPPER DIFFLUENCE IN THE REGION 
W OF THE RIDGE AXIS IS PRODUCING A WIDESPREAD CIRRUS CANOPY N OF 
15N W OF 124W AND IT IS POSSIBLE THAT THERE COULD BE SOME 
EMBEDDED SHOWERS ESPECIALLY NEAR THE ITCZ. AT THE SURFACE...A 
TROUGH HAS FORMED ROUGHLY ALONG 140W S OF 18N AND IS LIKELY 
CONTRIBUTING TO THE PRODUCTION OF SCATTERED SHOWERS.

$$
BERG