000
AXPZ20 KNHC 210324
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT MAR 21 2009

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 
0230 UTC.

...ITCZ...
THE ITCZ AXIS LIES ALONG A LINE FROM 08N83W TO 05N90W TO 01N109W 
03N127W TO 04N140W. NO SIGNIFICANT CONVECTION IS OCCURRING NEAR 
THE ITCZ AXIS.

...DISCUSSION...

THE UPPER LEVEL FLOW CONTINUES TO AMPLIFY N OF THE DISCUSSION 
AREA AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHEASTWARD...FORCING 
AN UPPER TROUGH TO DIG SOUTHWARD TOWARD THE DISCUSSION AREA. AN 
ASSOCIATED COLD FRONT N OF THE AREA CONTINUES ADVANCING 
SOUTHWARD. THE REMNANTS OF THIS FRONT ARE FORECAST TO AFFECT THE 
NORTHERN WATERS ON SUNDAY AND MONDAY. N WINDS OF 20 TO 30 KT 
WILL AFFECT AREAS IN THE WAKE OF THE FRONT...WHERE WAVE HEIGHTS 
OVER 14 FT IN NORTHWESTERLY SWELL WILL BE PRESENT. GALES ARE 
EXPECTED TO REMAIN N OF THE AREA...WHERE THE STRONGER SURFACE 
PRESSURE GRADIENT WILL BE LOCATED.

IN THE MEANTIME...A WEAK SURFACE RIDGE N OF THE DISCUSSION AREA 
CONTINUES TO DISSIPATE IN RESPONSE TO DECREASING DEEP LAYER 
SUBSIDENCE WITH THE AMPLIFICATION OF THE UPPER TROUGH. WAVE 
HEIGHTS UP TO 8 FT IN NORTHWESTERLY SWELL CONTINUE IN NORTH 
CENTRAL PORTIONS OF THE DISCUSSION AREA...BUT CONTINUE SUBSIDING 
AS THEY DEPART THEIR SOURCE REGION AND WINDS DIMINISH. THE 
ENHANCED SURFACE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF 
THE SURFACE HIGH ALSO IS ENHANCING NE TO E TRADE WINDS ACROSS 
THE REGION. THE QUIKSCAT PASS AROUND 20/1420 UTC SHOWED NE TO E 
WINDS UP TO 20 KT FROM 11N TO 17N W OF 130W...WITH WAVEWATCH 
GUIDANCE INDICATING SEAS TO 9 FT IN THIS AREA WITH NW SWELL. THE 
TRADES IN THIS AREA ARE EXPECTED TO PICK UP SUBSTANTIALLY ON 
SUNDAY AS A SURFACE HIGH BUILDS SOUTHWARD IN THE WAKE OF THE 
AFOREMENTIONED COLD FRONT. ALSO...SOUTHWESTERLY SWELL OF UP TO  
8 FT S OF THE AREA WILL MOVE NORTHWARD INTO THE AREA AND MERGE 
WITH NORTHWESTERLY SWELL ACROSS SOUTHERN PORTIONS OF THE AREA BY 
SUNDAY.

AS FOR CONVECTIVE ACTIVITY...UPPER LEVEL DIFFLUENCE N OF THE 
ITCZ AXIS IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 09N 
TO 13N BETWEEN 123W AND 130W. FARTHER TO THE E...DEEP LAYER DRY 
AIR AND STABLE ATMOSPHERIC CONDITIONS EMBEDDED WITHIN AN UPPER 
RIDGE ARE RESULTING IN FAIR WEATHER CONDITIONS S OF 16N E OF 96W.

GAP WINDS...
A PERSISTENT RIDGE OF SURFACE HIGH PRESSURE OVER MEXICO AND THE 
GULF OF MEXICO WILL SUPPORT A RELATIVELY STRONG SURFACE PRESSURE 
GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC DURING THE NEXT FEW 
DAYS. CORRESPONDINGLY...THE ASCAT PASS AROUND 20/1620 UTC 
DEPICTED N TO NE WINDS OF 20 TO 25 KT FUNNELING INTO THE GULF OF 
TEHUANTEPEC. STRONG SURFACE HIGH PRESSURE BUILDING SOUTHEASTWARD 
TOWARD THE MID-ATLANTIC STATES OF THE CONUS WILL STEEPEN THE 
PRESSURE GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC EVEN FURTHER 
DURING THE NEXT DAY. CORRESPONDINGLY...WINDS WILL INCREASE 
ACROSS A LARGER AREA IN THE GULF OF TEHUANTEPEC. COMPUTER MODEL 
GUIDANCE CONTINUES TO INDICATE THE LIKELIHOOD OF GALE FORCE 
WINDS FROM LATE TONIGHT THROUGH SATURDAY IN THE GULF OF 
TEHUANTEPEC...GIVEN THE STRONG PRESSURE GRADIENT SW OF THE 
SURFACE HIGH. SEAS WILL BUILD OVER 11 FT DOWNWIND OF THE GULF OF 
TEHUANTEPEC BY SATURDAY. ALSO...TRADE WINDS ACROSS THE CARIBBEAN 
CONTINUE WITH A PERSISTENT SURFACE LOW OVER NW COLOMBIA. THESE 
WINDS BLEED INTO THE GULFS OF PAPAGAYO AND PANAMA DURING THE 
NEXT FEW DAYS. THESE GAP WINDS ARE FORECAST TO BE STRONGEST LATE 
AT NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN 
THE PRESENCE OF DEEP LAYER DRY AIR.

$$

COHEN