000
AXPZ20 KNHC 172155
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT NOV 17 2007

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N77W 5N85W 8N105W 9N125W 9N140W. 
NUMEROUS MODERATE TO STRONG FROM 3N TO 7N E OF 82W. SCATTERED 
MODERATE WITHIN 60 NM OF AXIS BETWEEN 102W AND 112W...BETWEEN 
121W AND 125W...AND BETWEEN 135W AND 139W.

...DISCUSSION...

E OF 105W...
A DIGGING MID TO UPPER LEVEL TROUGH WHICH HAS SET UP OVER FAR 
W-CENTRAL MEXICO AND THE ADJACENT WATERS HAS ESSENTIALLY BROKEN 
DOWN THE UPPER RIDGE WHICH WAS LOCATED OVER SE MEXICO AND 
CENTRAL AMERICA... WITH BROAD SW/W FLOW STREAMING FROM THE FAR E 
PACIFIC WATERS INTO THE W CARIBBEAN. HOWEVER...A WELL-DEFINED 
MID-LEVEL RIDGE IS STILL ANCHORED ALONG 18N E OF 100W AND IS 
PRODUCING MODERATE SUBSIDENCE OVER MUCH OF THE REGION...BECOMING 
STRONGER S OF 9N TOWARD THE EQUATOR. FAIRLY DRY LOW-LEVEL AIR N 
OF THE ITCZ HAS KEPT SKIES MOSTLY CLOUD-FREE WITH THE EXCEPTION 
OF SCATTERED SHOWERS/TSTMS ON THE WINDWARD/EASTERN SIDES OF 
COSTA RICA AND PANAMA. BROKEN STRATOCUMULUS IN STREAMERS LIE S 
OF THE ITCZ DUE TO HIGHER MOISTURE VALUES AND INSTABILITY OVER 
COOLER OCEAN WATERS.

A 1614 UTC ASCAT PASS INDICATED WINDS OF 15 KT OVER THE GULF OF 
TEHUANTEPEC. GIVEN THE OBSERVED LOW BIAS OF ASCAT WINDS IT IS 
ESTIMATED THAT 20 KT WINDS ARE STILL OCCURRING IN THE REGION.  
WINDS WILL CONTINUE TO DIMINISH AND COULD BE BELOW 20 KT BY THIS 
EVENING...ALTHOUGH DIURNAL EFFECTS COULD CAUSE BRIEF INCREASES 
IN WIND SPEEDS ESPECIALLY SUN MORNING. ANOTHER SURGE BEGINS 
OVERNIGHT SUN INTO MON AND WINDS WILL ONCE AGAIN INCREASE TO 25 
TO 30 KT...POSSIBLY REACHING NEAR GALE CONDITIONS.

W OF 105W...
A DEEP-LAYERED TROUGH AXIS IS SWINGING ACROSS NW MEXICO FROM 
W-CENTRAL TEXAS TO SRN BAJA CALIFORNIA...AND HAS COME INTO 
PHASE WITH ANOTHER UPPER TROUGH LOCATED DEEPER WITHIN THE 
TROPICS ALONG 110W. MODERATE/STRONG SUBSIDENCE ASSOCIATED WITH 
THE NRN PART OF THE TROUGH IS PUSHING ACROSS MUCH OF NW MEXICO 
AND THE SRN BAJA PENINSULA AND IS PROVIDING AN EFFICIENT CAP TO 
THE MARINE LAYER W OF BAJA...WITH COASTAL FOG/STRATUS BANKED 
OVER THE W COAST N OF 26N. W OF THE TROUGH...A BROAD NE/SW 
ORIENTED UPPER RIDGE EXTENDS FROM 27N140W TO 30N130W AND IS 
PROVIDING ADDITIONAL SUBSIDENCE N OF 24 ON THE CUSP OF A 50-55 
KT WESTERLY SUBTROPICAL JET. THE JET ORIGINATES FROM A LARGE 
CUT-OFF LOW LOCATED ABOUT 300 NM SE OF THE BIG ISLAND OF 
HAWAII...AND BROAD DIFFLUENCE E OF THE LOW IS PRODUCING 
WIDESPREAD MID/HIGH LEVEL CLOUDINESS LYING WITHIN A BELT BETWEEN 
9N-24N FLOWING E TOWARDS MEXICO. MODEL GUIDANCE HAS BEEN 
SUGGESTING THAT SURFACE LOW PRES MAY DEVELOP BENEATH THIS AREA 
OF DIVERGENCE OVER THE NEXT 48 HRS OR SO BUT IT IS EXPECTED TO 
REMAIN W OF 140W AND MAY INCREASE EASTERLY WINDS TO 20-25 KT 
OVER THE FAR WRN PART OF THE DISCUSSION AREA.

$$
COBB