000
AXPZ20 KNHC 200916
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT SEP 20 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 
0845 UTC.

...SPECIAL FEATURES...

A BROAD AND ELONGATED AREA OF LOW PRESSURE IS LOCATED WITHIN 
THE ITCZ CENTERED A FEW HUNDRED NM SSW OF THE GULF OF 
TEHUANTEPEC. SATELLITE IMAGERY SHOWS A NE-SW STRETCHED AREA OF 
LOW TO MID LEVEL CYCLONIC TURNING WITH A FEW EMBEDDED CENTERS. 
MAIN EFFECTS OF THE SYSTEM AT THE MOMENT IS THE POTENTIAL FOR 
HEAVY RAINS ALONG THE PACIFIC COASTS OF GUATEMALA AND SOUTHERN 
MEXICO. INDEED...CURRENT IR IMAGERY SHOWS THE STRONGEST 
CONVECTION OVER THOSE AREAS AND THE GULF OF TEHUANTEPEC. 
CONVECTION ELSEWHERE IS DISORGANIZED WITH LITTLE SIGNATURE OF 
CURVED BANDING. GRADUAL DEVELOPMENT IS POSSIBLE OVER THE NEXT 
COUPLE OF DAYS AS THE SYSTEM MOVES SLOWLY WEST-NORTHWEST.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 95W/96W N OF 08N MOVING W 10 KT. THIS 
WAVE IS BECOMING TANGLED WITH THE BROAD LOW (SPECIAL FEATURE) 
LOCATED JUST TO ITS W. NONETHELESS...IT IS LIKELY ENHANCING THE 
HEAVY RAINS DISCUSSED ABOVE AND IT MAY HELP ADD VORTICITY AND 
DEVELOP THE LOW.

TROPICAL WAVE IS ALONG 105W FROM 06N TO 16N MOVING W 5-10 KT. 
DESPITE ALSO BEING EMBEDDED WITHIN THE BROAD LOW...THERE IS 
STILL EVIDENCE OF THIS FEATURE WITH A NARROW BAND OF SCATTERED 
MODERATE CONVECTION EXTENDING N OF 16N BETWEEN 104-106W. 

TROPICAL WAVE IS ALONG 121W FROM 07N TO 16N MOVING W 5-10 KT. 
THIS WAVE IS EASY TO LOCATE AS LOW-LEVEL TURNING IS WELL DEFINED 
AND THERE IS SOME EVIDENCE OF A WEAK CIRCULATION ALONG THE AXIS 
NEAR 11N. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM OF THE 
AXIS BETWEEN 09-14N. 

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N87W TO 12N97W TO 09N107W TO 
12N117W TO 09N130W TO 08N140W. SCATTERED MODERATE CONVECTION IS 
FROM 03N-07N BETWEEN 78W-89W...WITHIN 150 NM OF AXIS BETWEEN 
100W-110W...AND FROM 09N-12N BETWEEN 135W-138W.

...DISCUSSION...

W OF 110W...
A WEAK 1021 MB HIGH NEAR 27N136W IS ALLOWING LIGHT TRADES TO 
PREVAIL ACROSS MUCH OF THE SUBTROPICS. ONLY EXCEPTION IS NEAR 
THE COAST OF BAJA N OF 26N WHERE N TO NW WINDS ARE NEAR 20 
KT...DUE TO THE TYPICAL TIGHTENED PRES PATTERN OVER THE REGION. 
NW SWELLS OVER THE W WATERS HAVE SUBSIDED BELOW 8 FT AS 
CONFIRMED BY A 0430 Z ALTIMETER PASS...TOOK MENTION OUT OF THE 
HIGH SEAS TEXT ACCORDINGLY. A LOW-LEVEL TROUGH ALONG 137W FROM 
07N TO 15N IS PRODUCING SCATTERED CONVECTION WITHIN THE ITCZ AND 
ENHANCING NE 20 KT TRADES WITHIN 300 NM OF THE TROUGH AXIS. 

A MID TO UPPER HIGH IS CENTERED NEAR 18N121W WHILE A HIGHLY 
ELONGATED UPPER LOW IS LOCATED NEAR 29N147W. THIS PATTERN IS 
PRODUCING LITTLE SIGNIFICANT CLOUDINESS...IN FACT...CONFLUENCE 
BETWEEN THE UPPER FEATURES IS ENHANCING DRY AIR ACROSS MUCH OF 
THE REGION.  

E OF 110W...
A MID TO UPPER RIDGE IS CENTERED OVER SOUTHERN MEXICO WITH ITS 
ASSOCIATED NE TO E FLOW TRANSPORTING CONSIDERABLE MOISTURE OVER 
THIS PORTION OF THE EPAC. THE MOISTURE IS DEEPENED BY THE 
TROPICAL WAVES...ITCZ...AND SPECIAL FEATURE DISCUSSED ABOVE. 

GAP WINDS...A 0410 Z ASCAT PASS REVEALED N TO NE 20 KT WINDS IN 
THE GULF OF TEHUANTEPEC. WHILE THE GAP FLOW IS EXPECTED TO 
DIMINISH TODAY...ELY WINDS MAY INCREASE AS BROAD LOW PRESSURE 
ORGANIZES A FEW HUNDRED NM SW OF THE AREA.

$$
CANGIALOSI