000
AXNT20 KNHC 282358
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT JUN 28 2014

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL  
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF 
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE 
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE 
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL 
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2345 UTC.

...SPECIAL FEATURES...                                          

A BROAD LOW PRESSURE AREA IS LOCATED ABOUT 110 NM SE OF THE 
COAST OF SOUTH CAROLINA PRODUCING SCATTERED MODERATE 
THUNDERSTORMS IN BANDS OF THE COAST OF THE CAROLINAS AND WELL 
OFFSHORE OF THE GEORGIA COAST. ENVIRONMENTAL CONDITIONS ARE 
FAVORABLE FOR ADDITIONAL DEVELOPMENT OF THIS SYSTEM AS DRIFTS TO 
THE SOUTH OVER THE NEXT FEW DAYS AND THERE IS A MEDIUM 
PROBABILITY OF THIS SYSTEM BECOMING A TROPICAL CYCLONE WITHIN 48 
HOURS. PLEASE REFER TO THE ATLC TROPICAL WEATHER OUTLOOK UNDER 
AWIPS/WMO HEADERS MIATWOAT/ABNT20 KNHC FOR MORE DETAILS.

...TROPICAL WAVES... 

TROPICAL WAVE IS EMBEDDED IN THE ITCZ WITH AXIS EXTENDING FROM 
13N41W TO 5N41W MOVING WEST AT 20-25 KT. SSMI TPW AND SAHARAN 
AIR LAYER TRACKING IMAGERY INDICATE THE PRESENCE OF DRY AIR N OF 
THE ITCZ WHICH IS LIMITING THE CONVECTION TO SCATTERED SHOWERS 
WITHIN 180 NM OF THE AXIS S OF 10N. 

TROPICAL WAVE IS WEST OF THE ITCZ WITH AXIS EXTENDING FROM 
17N55W TO 06N56W MOVING WEST AT 15-20 KT. SAHARAN AIR LAYER 
TRACKING IMAGERY SHOW DRY AIR IN THE WAVE ENVIRONMENT N OF 10N. 
SCATTERED MODERATE CONVECTION IS LIMITED TO THE VICINITY OF THE 
ITCZ FROM 6N-9N BETWEEN 54W-58W.

TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS EXTENDING 
FROM 18N71W TO THE COLOMBIAN COAST AT 72W MOVING WEST NEAR 15 
KT. SSMI TPW IMAGERY SHOW DRY AIR IN THE NORTHERN ENVIRONMENT OF 
THE WAVE WHICH ALONG STRONG DEEP-LAYER WIND SHEAR OVER THE 
CENTRAL AND EASTERN CARIBBEAN HINDER DEEP CONVECTION. SCATTERED 
LOW TOPPED SHOWERS ARE WITHIN 180 NM EITHER SIDE OF THE AXIS S 
OF 15N.

TROPICAL WAVE IS OVER THE BAY OF CAMPECHE WITH AXIS EXTENDING 
FROM 21N92W TO 14N95W MOVING WEST AT 15 KT. THIS WAVE IS VERY 
WEAK AND BARELY DISCERNIBLE AS IT MOVES IN THE W-SW PERIPHERY OF 
A LOW LEVEL RIDGE. CONVECTION ASSOCIATED WITH THIS WAVE IS 
CONFINED TO THE EAST PACIFIC BASIN. 

...THE ITCZ/THE MONSOON TROUGH...                                
     
THE MONSOON TROUGH EXTENDS FROM THE COAST OF SENEGAL NEAR 10N14W 
TO 8N20W. THE ITCZ BEGINS NEAR 08N20W AND CONTINUES ALONG 07N30W 
TO E OF A TROPICAL WAVE NEAR 08N38W. IT THEN RESUMES W OF THE 
WAVE NEAR 06N42W TO 09N54W. SCATTERED MODERATE CONVECTION AND 
TSTMS ARE FROM 6N-11N E OF 20W. SCATTERED MODERATE CONVECTION IS 
WITHIN 120 NM EITHER SIDE OF THE WAVE FROM THE COAST OF AFRICA 
TO 28W. 

...DISCUSSION...

...THE GULF OF MEXICO...                                     

SURFACE RIDGING DOMINATES ACROSS THE GULF BEING SUPPORTED BY A 
MIDDLE LEVEL ANTICYCLONE COVERING THE EASTERN HALF OF THE BASIN. 
THE SURFACE RIDGE IS ANCHORED BY A 1022 MB HIGH NEAR ABOUT 60 NM 
S OF APALACHICOLA FLORIDA. THIS HIGH WAS PROVIDING THE GULF 
WITH E TO SE WINDS OF 10-15 KT...EXCEPT W OF 92W WHERE WINDS ARE 
UP TO 20 KT. IN THE UPPER LEVELS...A SHARP NEGATIVELY TILTED 
TROUGH EXTENDS FROM OKLAHOMA THROUGH EASTERN TEXAS TO THE NW 
GULF WHILE THE EASTERN PERIPHERY OF A RIDGE ANCHORED OVER SW 
MEXICO COVERS THE BAY OF CAMPECHE. THIS WIND PATTERN ALOFT IS 
STRONGLY DIFFLUENT OVER THE GULF BETWEEN 88W AND 92W. THE 
PRESENCE OF DRY AIR OVER THE GULF PREVENTED THE DEVELOPMENT OF 
CONVECTION IN THIS AREA. CONVECTION WAS CONFINED TO THE EXTREME 
WESTERN GULF WITHIN 60-90 NM OF THE COAST OF MEXICO NEAR 
TAMPICO. HIGH PRESSURE WILL PREVAIL ACROSS THE BASIN FOR THE 
NEXT COUPLE OF DAYS WHILE A TROPICAL WAVE CURRENTLY IN THE BAY 
OF CAMPECHE MOVES TOWARD SOUTHERN MEXICO AND THE E PACIFIC 
WATERS.

...THE CARIBBEAN SEA...                                       

THE WESTERN EXTENT OF AN UPPER LEVEL TROUGH OVER THE SUBTROPICAL 
ATLANTIC EXTENDS THROUGH THE WINDWARD PASSAGE TO AN UPPER LEVEL 
CYCLONE NEAR 19N82W. MODERATE TO STRONG SUBSIDENCE WAS NOTED 
OVER THE NW CARIBBEAN NEAR THE UPPER LOW. AXIS OF AN UPPER LEVEL 
JET STREAK EXTENDS FROM THE E COAST OF NICARAGUA ACROSS THE 
CARIBBEAN ALONG 15N TO PUERTO RICO AND THE NORTHERN LEEWARD 
ISLANDS. SATELLITE DERIVED WINDS WERE 40-55 KT. OVERALL 
SUBSIDENCE AND THE PRESENCE OF SAHARAN DUST PER LATE DAY VISIBLE 
SATELLITE IMAGERY WAS KEEPING MOST OF THE CARIBBEAN UNDER FAIR 
BUT HAZY CONDITIONS. SCATTERED MODERATE TO STRONG THUNDERSTORMS 
WERE OVER THE FAR SOUTHERN CARIBBEAN WHERE IN THE VICINITY OF THE 
THE MONSOON TROUGH. ELSEWHERE AT THE SURFACE...A SURFACE TROUGH 
IS W OF THE WINDWARD ISLANDS WITH AXIS EXTENDING FROM 17N62W TO 
14N64W GENERATING SHOWERS AND THUNDERSTORMS S OF 15N E OF 64W. 
THE PRESSURE GRADIENT BETWEEN THE ATLANTIC RIDGE AND THE MONSOON 
TROUGH IS MAINTAINING 20-25 KT TRADES IN THE CENTRAL CARIBBEAN 
AND 10-20 KT WINDS IN BOTH THE WESTERN AND EASTERN CARIBBEAN. A 
NEW TROPICAL WAVE WILL BE ENTERING THE E CARIBBEAN LATE SUNDAY. 

...HISPANIOLA...             

THE PRESENCE OF SAHARAN DRY AIR HAS INHIBITED CONVECTION IN THE 
AREA WITH THE EXCEPTION OF AN ISOLATED THUNDERSTORM ERUPTING 
OVER THE INTERIOR OF EASTERN HAITI. SUPPORT FOR THIS CONVECTION 
WAS PRIMARILY DUE TO THE PRESENCE OF STRONG UPPER LEVEL WINDS 
WHICH ALLOWED FOR MID LEVEL INSTABILITY. THE CONTINUED PRESENCE 
OF THE SAHARAN AIR LAYER IN THE AREA OVER THE NEXT COUPLE OF 
DAYS SHOULD RESULT IN DELAYED DEVELOPMENT OF AFTERNOON 
CONVECTION WITH GENERALLY LESS COVERAGE THAN IS TYPICALLY 
EXPECTED.  

...THE ATLANTIC OCEAN...

AN UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC CIRCULATION NEAR 
32N50W SOUTHWESTWARD THROUGH 23N60W 21N70W TO THE WINDWARD 
PASSAGE. MODERATE SUBSIDENCE WAS NOTED WITHIN 240 NM SE OF THE 
TROUGH AXIS. AN UPPER LEVEL ANTICYCLONE WAS LOCATED TO THE NW OF 
THE TROUGH OVER NE FLORIDA WHICH GOVERNED THE FLOW OVER THE 
ATLANTIC W OF 73W. THE WEAK LOW PRESSURE OFF THE COAST OF SOUTH 
CAROLINA WAS EMBEDDED WITHIN THE EASTERN PERIPHERY OF THE 
ANTICYCLONE AND UNDERGOING SOME NORTHWESTERLY SHEAR. THE AREA OF 
LOW PRESSURE IS SUPPORTING SCATTERED MODERATE THUNDERSTORMS IN 
BANDS OF THE COAST OF THE CAROLINAS AND WELL OFFSHORE OF THE 
GEORGIA COAST. REFER TO THE SPECIAL FEATURES SECTION FOR MORE 
INFORMATION. ELSEWHERE OVER THE ATLANTIC...A BROAD SURFACE RIDGE 
ANCHORED BY A 1029 MB HIGH NEAR 33N40W EXTENDED THROUGH 28N55W 
TO THE BAHAMAS AND SUPPORTED GENERALLY FAIR WEATHER CONDITIONS. 

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE

$$
COBB