000
AXPZ20 KNHC 190922
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT JAN 19 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 5N77W 7N90W 6N110W 9N127W 4N140W. NO 
SIGNIFICANT CONVECTION.

...DISCUSSION...

N OF 20N...
A BROAD LONGWAVE TROUGH REMAINS ANCHORED ACROSS MUCH OF NORTH 
AMERICA BUT HAS FLATTENED OUT A BIT AS IT EXTENDS SOUTHWARD 
ACROSS MEXICO AS AN EMBEDDED SHORTWAVE LIFTS NE ACROSS THE RIO 
GRANDE VALLEY. ANOTHER SHORTWAVE OR TWO ARE LOCATED OVER NW 
MEXICO AND SOUTHERN CALIFORNIA...BUT THESE ARE SOMEWHAT DETACHED 
FROM THE MAIN LARGE-SCALE FLOW AND WILL NOT BE ABLE TO DEEPEN 
THE LONGWAVE ANY FURTHER. CONFLUENCE INTO THE BASE OF THE TROUGH 
INITIATES A 70-100 KT JET STREAK ACROSS NORTHERN MEXICO AND IS 
ALSO PRODUCING MODERATE/STRONG SUBSIDENCE N OF 22N BETWEEN 
97W-122W. THERE IS MORE CLOUDINESS...BOTH UPPER LEVEL AND LOWER 
LEVEL...LOCATED W OF 122W PARTIALLY DUE TO A NEGATIVELY-TITLED 
UPPER TROUGH EXTENDING FROM 25N130W NW PAST 30N136W AND SLIGHTLY 
MORE AVAILABLE ATMOSPHERIC MOISTURE. HIGH PRES ACROSS THE 
SOUTHERN ROCKIES AND GREAT BASIN CONTINUES TO PRODUCE 
NORTHWESTERLY WINDS TO 20 KT OVER THE GULF OF CALIFORNIA...BUT 
THESE SHOULD ABATE BY 36 HOURS (ON SUN) THEN TURN SOUTHERLY AS 
LOW PRES DEVELOPS OVER NEVADA.

S OF 20N...
WESTERLY UPPER LEVEL WINDS DOMINATE THE TROPICS EXTENDING FROM 
140W TO 105W...THEN TURN MORE SOUTHWESTERLY TOWARDS CENTRAL 
AMERICA. MAXIMUM JET CORE SPEEDS ARE NEAR 75 KT AND ARE CENTERED 
ALONG 9N PRIMARILY OVER WESTERN AREAS. A CONTINUOUS BAND OF 
UPPER LEVEL MOISTURE LIES NEAR THE JET STREAM AND EVENTUALLY 
MOVES INLAND ACROSS S/CENTRAL MEXICO WHILE MODERATE/STRONG 
SUBSIDENCE CONTINUES TO DOMINATE THE REGION E OF 100W. A 
LOW-LEVEL TROUGH HAS DEVELOPED ALONG 128W S OF 12N BUT IS ONLY 
PRODUCING ISOLATED SHOWERS FROM 8N-11N BETWEEN 120W-128W.

THE GALE WARNING FOR THE GULF OF TEHUANTEPEC HAS BEEN UPGRADED 
TO A STORM WARNING BASED ON THE LATEST NUMERICAL GUIDANCE. 
FORECAST VERTICAL SOUNDINGS FROM BOTH THE 00Z GFS AND 00Z NAM 
INDICATE THAT MIXED LAYER WINDS WILL REACH 50 KT BY TONIGHT AND 
LIKELY LAST FOR ABOUT 12 HOURS OR SO. IN ADDITION...THESE MODELS 
ASSUME SURFACE TEMPERATURES OF 23C AND 21C RESPECTIVELY BUT 
SATELLITE-DERIVED SEA SURFACE TEMPERATURE DATA CURRENTLY SHOW 
TEMPERATURES NO LOWER THAN 25-26C. THEREFORE...IT IS POSSIBLE 
THAT VERTICAL MIXING COULD BE STRONGER THAN INDICATED IN THE 
MODELS...WHICH WOULD MAKE IT EASIER TO REACH STORM FORCE. GALE 
CONDITIONS ARE LIKELY TO CONTINUE THROUGH MON AFTERNOON.

$$
BERG