000
AXPZ20 KNHC 200342 RRA
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT SEP 20 2008

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC.

...SPECIAL FEATURES...

SOME GRADUAL DEVELOPMENT OF THE BROAD AREA OF LOW TO MID LEVEL 
CYCLONIC FLOW AND SCATTERED CONVECTION WEDGED BETWEEN THE 
TROPICAL WAVES ALONG 104W AND 94W FROM 08N AND 15N IS POSSIBLE 
OVER THE NEXT COUPLE OF DAYS.  WITHOUT VISIBLE SATELLITE IMAGERY 
OR A SCATTEROMETER PASS...IT IS VERY DIFFICULT TO IDENTIFY A LOW 
LEVEL CENTER...IF THERE IS ONE...AT THIS TIME.  CONVECTION 
WITHIN THIS AREA IS PRESENTLY UNDER THE INFLUENCE OF STRONG 
UPPER EASTERLY SHEAR...BUT IT IS EXPECTED TO SLOWLY MOVE W OR NW 
UNDER A SLIGHTLY IMPROVED UPPER LEVEL ENVIRONMENT OVER THE NEXT 
COUPLE OF DAYS.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 94W N OF 08N TO THE GULF OF TEHUANTEPEC IS 
MOVING W 5 TO 10 KT. SCATTERED MODERATE CONVECTION CAN BE FOUND 
WITHIN 75 NM OF TROPICAL WAVE ALONG 94W N OF 14N. AS THIS WAVE 
MOVES W IT WILL BECOME ABSORBED INTO THE AREA OF DISTURBED 
WEATHER DESCRIBED ABOVE UNDER SPECIAL FEATURES.

TROPICAL WAVE ALONG 104W BETWEEN 06N AND 16N IS MOVING W 5 TO 10 
KT.  THIS TROPICAL WAVE IS EMBEDDED WITHIN THE ITCZ AND IS 
ASSOCIATED WITH THE BROAD AREA OF ISOLATED MODERATE CONVECTION 
FOUND WITHIN 120 NM OF THE ITCZ AXIS FROM 100W TO 110W AS WELL 
AS THE SCATTERED MODERATE CONVECTION TO ITS E FROM 100W TO 102W 
BETWEEN 13N AND 15N.

TROPICAL WAVE ALONG 121W FROM 6N TO 15N IS MOVING W 5 KT. A WEAK 
LOW-LEVEL CIRCULATION CAN BE FOUND ON THE WAVE AXIS NEAR 
10N121W. ISOLATED MODERATE CONVECTION CAN BE FOUND WITHIN 90 NM 
OF THIS TROPICAL WAVE BETWEEN 09N AND 12N.

...ITCZ...
ITCZ AXIS LIES ALONG 10N86W TO 11N94W TO 09N110W TO 11N118W TO 
10N136W. ISOLATED MODERATE CONVECTION CAN BE FOUND WITHIN 120 NM 
OF AXIS FROM 100W TO 110W.

...DISCUSSION...

A LOW LEVEL TROUGH ALONG 136W IS GENERATING MODERATE ISOLATED 
MODERATE CONVECTION WITHIN 120 NM OF TROUGH ALONG 136W BETWEEN 
09N AND 12N.  THIS IS A RELATIVELY DEEP TROUGH THAT LIES IN A 
REGION OF LIGHT DIFFLUENT UPPER LEVEL WINDS AND PRECIPITABLE 
WATER VALUES IN EXCESS OF 2.25 INCHES.  EXPECT THE CONVECTION 
ASSOCIATED WITH THIS SYSTEM TO BE SLOW TO MOVE...BUT IT WILL 
LIKELY LOSE ITS SURFACE REFLECTION OVER THE NEXT FEW DAYS.  THE 
INVERTED MID LEVEL TROUGH IN THE VICINITY OF 130W IS SLOWING THE 
PROGRESS OF THE TROPICAL WAVE ALONG 121W WHICH IS EXPECTED TO BE 
FORCED N BY THE E EDGE OF THE TROUGH AND DISSIPATE OVER THE NEXT 
FEW DAYS.

A WEAK TROUGH OVER NW WATERS WILL DISSIPATE OVER THE NEXT DAY. 
WHILE WINDS ARE NOT EXPECTED TO APPROACH 20 KT AT THE 
SURFACE...NW SWELL SHOULD CONTINUE TO ELEVATE SEAS TO 8 FT FOR 
AT LEAST THE NEXT 12 HOURS.

THE REBUILDING HIGH PRESSURE AT THE SURFACE OVER N WATERS IS 
INDUCING A PRESSURE GRADIENT ALONG THE NORTHERN BAJA CALIFORNIA 
COAST...FORCING WINDS TO 20 KT.  

THE COLD FRONT THAT PENETRATED THE BAY OF CAMPECHE OVER THE LAST 
SEVERAL DAYS HAS WEAKENED...ALLOWING WINDS TO DIMINISH OVER THE 
GULF OF TEHUANTEPEC TO LESS THAN 20 KT OVER THE NEXT 12 HOURS OR 
SO.

$$
SCHAUER CLARK