000
AXPZ20 KNHC 301604
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED APR 30 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
ITCZ AXIS IS ALONG 06N77W TO 07N88W TO 08N120W TO 05N125W TO 
07N132W TO 03N140W. NUMEROUS MODERATE SCATTERED STRONG ALONG 
COLOMBIAN COAST FROM 04N TO 07N E OF 80W. SCATTERED MODERATE 
WITHIN 60 NM N OF AXIS BETWEEN 130W AND 135W.

...DISCUSSION...

E OF 100W...UPPER RIDGE ANCHORED OVER NORTHERN SOUTH AMERICA 
EXTENDS WESTWARD ALONG 10N...SOUTH OF A LOW AMPLITUDE UPPER 
TROUGH MOVING ACROSS CENTRAL MEXICO. SOUTHWEST WINDS ALOFT 
BETWEEN THESE FEATURES IS PROVIDING UPPER EXHAUST TO A LARGE 
CLUSTER OF THUNDERSTORMS OFF THE COLOMBIAN COAST. THE MAIN 
INSTIGATOR OF THIS CONVECTION IS MODERATE SOUTHWEST BOUNDARY 
LAYER WINDS CONVERGING WITH 10 TO 15 KT NORTHERLY WINDS IN THE 
GULF OF PANAMA...ALONG WITH DRAINAGE FLOW OFF MOUNTAINOUS 
COLOMBIAN COAST. THE CONVECTION IS WEAKENING AS THE DRAINAGE 
FLOW TAPERS OFF...BUT A NOCTURNAL REFLARING IS LIKELY. LOOKING 
AHEAD...THE GFS MODEL IS SHOWING INCREASED SW WINDS IN THE GULF 
OF PANAMA OVER THE NEXT COUPLE OF DAYS...IN DISAGREEMENT WITH 
OTHER GLOBAL MODELS. THE STRONGER WINDS ARE LIKELY AN ARTIFACT 
OF CONVECTIVE FEEDBACK...ALTHOUGH SLIGHT STRONGER NORTHERLY 
WINDS ARE POSSIBLE THROUGH THE ISTHMUS. FURTHER NORTH...A SHIP 
REPORT STRONG WINDS THROUGH THE GULF OF PAPAGAYO OFF COSTA RICA 
THIS MORNING. THIS IS A CONTINUATION OF FUNNELING EFFECTS 
ENHANCING SURFACE FLOW ON THE NORTH SIDE OF A TROUGH RUNNING 
PARALLEL AND TO THE NORTH OF THE ITCZ THROUGH PANAMA AND COSTA 
RICA. MODEST GAP WINDS IN THE GULF OF TEHUANTEPEC CONTINUE TO 
DIMINISH AS HIGH PRES LOWERS IN THE GULF OF MEXICO. 

W OF 100W...MID/UPPER RIDGE AXIS ALONG 110W WILL FLATTEN OUT 
TONIGHT AHEAD OF A SHARP UPPER TROUGH EXTENDING FROM THE 
NORTHERN ROCKIES TO SOUTHERN CALIFORNIA TO 25N140W. THE TROUGH 
STALLS OVERNIGHT...THEN BECOMES MORE AMPLIFIED THROUGH FRIDAY AS 
AN UPPER RIDGE BUILDS NW OF THE AREA NEAR 35N140W. AT THE 
SURFACE 1033 MB HIGH PRESSURE CENTERED NEAR 36N140W AND 
ASSOCIATED WITH THE UPPER RIDGE WILL SHIFT SLOWLY SOUTHEASTWARD 
THROUGH FRIDAY. THIS IS MAINTAINING STRONG NORTHERLY WINDS OFF 
THE NORTHERN BAJA COAST...AND A LARGE SWATH OF NE TO E TRADES 
SOUTH OF THE HIGH. THE WINDS DIMINISH GRADUALLY OVER THE NEXT 
COUPLE OF DAYS AS THE RIDGE CONTINUES MORE SOUTHEASTWARD. 
FURTHER SOUTH...SATELLITE IMAGERY SHOW WEAK CYCLONIC TURNING 
NEAR 08N120W ALONG THE ITCZ. A MID/UPPER TROUGH EXTENDING FROM 
20N140W TO 05N125W MAY BE CUTTING OFF AN MID LEVEL CYCLONE IN 
THE AREA. QUIKSCAT DATA SHOW ONLY BROAD CYCLONIC ROTATION 
INDICATIVE OF A SURFACE TROUGH. CONVECTION IS VERY MINIMAL AS 
WELL...ALTHOUGH FRESH TRADE WIND FLOW IS EXPECTED TO SHIFT SOUTH 
AS SURFACE HIGH TO THE NORTH SHIFTS SOUTHEAST...PROVIDING BETTER 
LOW LEVEL CONVERGENCE. IN ADDITION SOME UPPER DIVERGENCE REMAINS 
IN PLACE ON SOUTHEAST SIDE OF UPPER TROUGH...SO SOME INCREASE IN 
CONVECTION IS POSSIBLE IN THIS AREA OVER THE NEXT COUPLE OF 
DAYS. ANOTHER SURFACE TROUGH IS NOTED FURTHER WEST ALONG THE 
ITCZ NEAR 132W...AT THE SOUTHEAST BASE OF THE UPPER TROUGH. 
MODERATE CONVECTION IS FLARING IN THIS AREA AS NOTED ABOVE. 


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CHRISTENSEN