000
AXPZ20 KNHC 191603
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI DEC 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 0930 UTC.

...ITCZ...
FROM 06N77W TO 07N85W TO 07N90W TO 07N101W TO 10N118W TO 09N126W 
TO 07N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION 
WILL CONTINUE THE NEXT 12 HOURS WITHIN 90 NM OF AXIS BETWEEN 
108W AND 127W...BETWEEN 106W AND 91W...AND ALONG THE COLUMBIA 
COASTLINE TO 07N.     

...DISCUSSION...
AN OMEGA BLOCKING PATTERN CONTINUES ACROSS THE EAST HALF OF THE 
PACIFIC AND ACROSS CENTRAL AMERICA AND INTO THE GULF OF MEXICO 
TODAY. AN UPPER LEVEL LONGWAVE TROUGH IS DIGGING THROUGH 42N120W 
TO 36N121W TO 30N129W TO AN UPPER LOW NEAR 26N133W EXTENDING S 
INTO THE ITCZ NEAR 07N132W. ON OLD AND LINGERING MIDDLE TO UPPER 
LEVEL CYCLONIC CIRCULATION CENTER...AND ASSOCIATED WEAK SW TO NE 
ALIGNED TROUGH...HAS BEEN NUDGED SOUTHEASTWARD BY THE LONGWAVE 
TROUGH DURING THE PAST 48 HOURS AND WAS CENTERED NEAR 12N125W. 
JET ENERGY DIVING OVER A HIGH AMPLITUDE RIDGE ALONG 152W AND 
INTO THE BACK SIDE OF THE LONGWAVE TROUGH WILL AID IN THE 
INTENSIFICATION AND FURTHER SOUTHWARD MOVEMENT OF THE UPPER LOW 
NEAR 26N133W DURING THE NEXT 48 HOURS...WITH THE UPPER LOW 
FORECAST TO CUTOFF FROM MEAN FLOW AND THEN RETROGRADE W TO SW 
DURING THE NEXT SEVERAL DAYS. THIS UPPER LOW IS ALSO SUPPORTING 
A FRONTAL BOUNDARY THAT HAS ENTERED NW PORTIONS OF THE AREA AND 
EXTENDED FROM 32N132W ARCHING TO 27N140W. NEAR GALE FORCE WINDS 
AND MODERATE NW SWELL ARE OCCURRING BEHIND THIS FRONT...AND WILL 
SHIFT S AND SE INTO THE AREA DURING THE NEXT 48 HOURS. 

E OF THIS FRONT AND HALFWAY TO THE S CALIFORNIA COAST IS A 1027 
MB SURFACE HIGH. THE OLD AND LINGERING MID TO UPPER TROUGH 
MENTIONED ABOVE HAS HELPED TO INDUCE LOW LEVEL TROUGHING FROM 
THE ITCZ AT 117W...NORTH NORTHEASTWARD TO NEAR 17N. THE PRESSURE 
GRADIENT BETWEEN THE SURFACE HIGH AND THIS INDUCED INVERTED 
TROUGH IS MAINTAINING A BROAD SWATH OF 20 TO 25 KT NE WINDS...N 
AND W OF THE LOW LEVEL TROUGH AND THE ITCZ...FROM 28N120W TO 
BEYOND 14N140W. WITHIN THIS SWATH OF FRESH NE WINDS SEAS ARE 
RUNNING 8 TO 10 FT AND WILL INCREASE TO 10 TO 12 FT BETWEEN 16N 
AND 21N DURING THE NEXT 36 HOURS. THE SURFACE HIGH IS ALSO 
USHERING NORTHERLY WINDS OF 20 TO 25 KT ALONG THE W COAST OF 
BAJA CALIFORNIA S TO 25N...WITH INCREASING WINDS AND SEAS 
EXPECTED TODAY THROUGH THE LENGTH OF THE GULF OF CALIFORNIA...TO 
AROUND 20 KT AND 6 FT. 

ACTIVE CONVECTION IS EXPECTED TO CONTINUE ACROSS A BROAD AREA 
BETWEEN THE ITCZ AND 22N AND BETWEEN 132W AND 110W AS THE 
DIGGING UPPER LOW INTERACTS FAVORABLY WITH ABUNDANT MOISTURE IN 
THE VICINITY OF THE LOW LEVEL INVERTED TROUGH ALONG 117W. S TO 
SW WINDS ALOFT ACROSS THIS CONVECTIVELY ACTIVE AREA WILL 
CONTINUE TO TRANSPORT UPPER LEVEL MOISTURE AND CONVECTIVE DEBRIS 
ACROSS THE BAJA AND THE NORTH HALF OF MEXICO DURING THE NEXT 
SEVERAL DAYS.  

A NEARLY STATIONARY FRONT PASSES THROUGH 26N109W TO 22N112W TO 
19N122W TO 16N128W. SCATTERED MODERATE SHOWERS AND ISOLATED 
THUNDERSTORMS WERE OCCURRING WITHIN 90 NM OF THIS 
BOUNDARY...MAINLY ACROSS THE CENTRAL GULF OF CALIFORNIA. 

GAP WINDS...
N-NE WINDS OF 20-25 KT THROUGH THE GULF OF TEHUANTEPEC AND 
PAPAGAYO ARE EXPECTED TO DIMINISH TO LESS THAN 20 KT BY 36 HOURS 
WHILE N WINDS OF AROUND 20 KT THROUGH THE GULF OF PANAMA WILL 
DIMINISH TO LESS THAN 20 KT BY 24 HOURS. 

$$
STRIPLING