[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN JUN 16 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1800 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IN THE WESTERN CARIBBEAN EXTENDS FROM 21N81W TO
17N82W TO 12N82W DRIFTING W AT 5 KT. OBSERVATIONS FROM GRAND
CAYMAN AND BUOY 42057 INDICATE WINDS ARE SLIGHTLY NE...HINTING
THAT THE WAVE AXIS HAS NOT YET PASSED 81W AT THE SURFACE...IN
ALMOST THE SAME POSITION AS 06 UTC. IN ADDITION...THE MORNING
SOUNDING FROM GRAND CAYMAN INDICATED NE TO E WINDS THROUGH H7.
NUMEROUS MODERATE TO SCATTERED STRONG CONVECTION IS NOTED FROM
16N TO 18N BETWEEN 80W AND 86W...AND FROM 12N TO 15N BETWEEN 80W
AND 82W. THE TROPICAL WAVE IS INTERACTING WITH AN UPPER CYCLONE
CENTERED OVER BELIZE...GUATEMALA AND WESTERN HONDURAS...WHICH IS
ENHANCING THE CONVECTION. THE TROPICAL WAVE IS AMPLIFYING AND
SLOWLY DOWN...AND IN CONJUNCTION WITH THE UPPER CYCLONE WILL
BRING CONTINUED CONVECTION TO THE NW CARIBBEAN...AND HEAVY
RAINFALL OVER NORTHERN CENTRAL AMERICA AND SOUTHERN MEXICO OVER
THE NEXT COUPLE OF DAYS.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS NORTH AFRICA AND CROSSES THE
COAST OF SENEGAL NEAR 14N16W THEN CONTINUES TO 11N20W. THE ITCZ
CONTINUES FROM 11N20W TO THE COAST OF FRENCH GUIANA NEAR 04N52W.
SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM N OF THE
AXIS W OF 38W.

...DISCUSSION...

GULF OF MEXICO...
A FEW THUNDERSTORMS PERSIST OFF THE SE LOUISIANA AND MISSISSIPPI
COASTLINES THIS AFTERNOON...SUPPORTED BY A WEAK UPPER SHORT WAVE
TROUGH DIGGING THROUGH THE NE GULF. A STATIONARY FRONT THAT
EXTENDED ACROSS CENTRAL FLORIDA INTO THE NE GULF OVERNIGHT HAS
SINCE DISSIPATED. THIS HAS LEFT A BROAD SURFACE RIDGE EXTENDING
FROM NORTH FLORIDA TO SOUTH TEXAS. SCATTEROMETER AND BUOY DATA
SHOW GENERALLY LIGHT TO MODERATE E TO SE FLOW TO THE SOUTH OF
THE RIDGE AXIS...EXCEPT FOR SE WINDS 15 TO 20 KT OF THE COAST OF
TAMAULIPAS IN NE MEXICO. THE SHORT WAVE TROUGH IS IN PHASE WITH
AN ELONGATED UPPER CYCLONE CENTERED S OF THE AREA OVER NORTHER
CENTRAL AMERICA. NORTHERLY FLOW ALOFT ON THE WESTERN SIDE OF
THIS TROUGH IS KEEPING THE MAJORITY OF THE GULF CLOUD FREE. THE
UPPER CYCLONE IS SUPPORTING A TROPICAL WAVE MOVING THROUGH THE
NW CARIBBEAN. THE N PORTION OF A TROPICAL WAVE WILL PASS W
ACROSS THE YUCATAN BASIN TONIGHT AND MON AND PASS ACROSS THE BAY
OF CAMPECHE TUE THROUGH LATE THU NIGHT WITH LOW PRESSURE
POSSIBLY DEVELOPING ALONG THE WAVE S OF 20N. THIS WILL INCREASE
THE SE FLOW OVER THE SW GULF TUE INTO WED.

CARIBBEAN SEA...
A MID LEVEL CIRCULATION ASSOCIATED WITH THE TROPICAL WAVE OVER
THE WESTERN CARIBBEAN APPEARS TO BE GETTING A LITTLE BETTER
ORGANIZED...ALTHOUGH IT ALSO APPEARS TO MOVING OVER THE EASTERN
PORTIONS OF HONDURAS AND NE NICARAGUA. JUDGING FROM SURFACE
OBSERVATIONS ALONE...THERE DOES NOT YET APPEAR TO BE A WELL
DEFINED SURFACE CIRCULATION...JUST AN AREA OF BROAD CYCLONIC
TURNING W OF 78W. ELSEWHERE E OF 80W...A FEW SHOWERS MAY BE
ACTIVE IN FRESH TRADE WIND FLOW ACROSS THE CARIBBEAN AND
TROPICAL N ATLC...BUT SKIES REMAIN MOSTLY CLOUD FREE. MEANWHILE
A AREA OF SAHARAN DUST TRACKING ACROSS THE ATLC WILL CONTINUE TO
PUSH OVER THE LEEWARD ISLANDS THROUGH PUERTO RICO. WHILE THIS IS
LOWERING VISIBILITIES SLIGHTLY...THE MAIN IMPACT COULD BE
SLIGHTLY STRONGER WIND GUSTS NEAR THUNDERSTORMS.

ASIDE FROM THE WEATHER IN THE NW CARIBBEAN ASSOCIATED WITH THE
TROPICAL WAVE DISCUSSED ABOVE...A SIMILAR SCENARIO MAY BE
GETTING ORGANIZED THAT WILL IMPACT THE TROPICAL N ATLC AND
EASTERN CARIBBEAN OVER THE NEXT TWO TO THREE DAYS. AN UPPER LOW
WILL CUT OFF WELL N OF THE ISLANDS AND DRIFT SOUTH. THIS WILL
INTERACT WITH A WEAK A COUPLE OF PERTURBATIONS NOW EMBEDDED IN
THE ITCZ AND MOVING THROUGH FRENCH GUIANA. THE UPPER CYCLONE
WILL ALLOW A TROUGH TO AMPLIFY OVER THE EASTERN
CARIBBEAN...DRAWING UP DEEP LAYER MOISTURE ACROSS THE TROPICAL N
ATLC...LESSER ANTILLES...AND EASTERN CARIBBEAN MON THROUGH TUE.

MEANWHILE THE GRADIENT WILL TIGHTEN BETWEEN THE SUBTROPICAL
RIDGE WILL BUILD TO THE N OF THE AREA AND THE TROUGH OVER THE
EASTERN CARIBBEAN AND DEVELOPING LOW PRES OVER THE WESTERN
CARIBBEAN TO ALLOW FRESH TO STRONG TRADES ACROSS THE ENTIRE
BASIN THROUGH MID WEEK.

HISPANIOLA...
A SHARP UPPER TROUGH EXTENDING FROM BERMUDA TO THE SOUTHERN
BAHAMAS IS ENHANCING A LARGE AREA OF CONVECTION OFF THE NORTH
COAST OF HISPANIOLA CURRENTLY. OUTFLOW BOUNDARIES FROM THIS
CONVECTION ARE NOTED ON VISIBLE SATELLITE IMAGERY AND WILL
REINFORCE AFTERNOON SEA BREEZES OVER THE NORTHERN PORTIONS OF
THE ISLAND. THE APPROACHING UPPER TROUGH WILL SHIFT THE
FAVORABLE UPPER DYNAMICS TO OVER THE ISLAND THROUGH THIS
EVENING...RESULTING IN THE POTENTIAL FOR THUNDERSTORMS ACROSS
HISPANIOLA INTO THE LATE EVENING BEFORE SHIFTING E OF THE AREA
LATE TONIGHT. A LAYER OF SAHARAN DUST INFILTRATING INTO THE
EASTERN CARIBBEAN MAY INTERACT WITH THESE THUNDERSTORMS TO
PRODUCE STRONG GUSTS. AN UPPER LOW IS EXPECTED TO CUT OFF AT THE
BASE OF THE TROUGH THROUGH MON...AND SHIFT TO THE NE OF
HISPANIOLA. THIS WILL ALLOW FOR SLIGHTLY DRIER AIR ALOFT AND
WITH A TREND FOR LESS FAVORABLE CONDITIONS FOR THUNDERSTORM
DEVELOPMENT MON INTO TUE.

ATLANTIC OCEAN...
A SHARP UPPER TROUGH FROM BERMUDA TO THE SOUTHERN BAHAMAS IS
SUPPORTING A LARGE AREA OF SHOWERS AND THUNDERSTORMS S OF 22N
BETWEEN 70W AND 73W...ROUGHLY BETWEEN HISPANIOLA AND THE
SOUTHERN BAHAMAS/TCI. IS SHOWING SIGNS OF CUTTING OFF INTO AN
UPPER CYCLONE N OF PUERTO RICO THROUGH MON. THE CONVECTION WILL
PERSIST AHEAD OF THE TROUGH AS IT SHIFTS TO THE SE AND E THROUGH
TONIGHT. THE UPPER TROUGH IS SUPPORTING THE MOVEMENT OF A WEAK
COLD FRONT ACROSS THE SW N ATLC...EXTENDING FROM 31N58W TO
26N70W. THIS FEATURE WILL CONTINUE WEAKEN AND SLOW AS IT DRIFTS
E...EVENTUALLY DISSIPATING BY LATE MON/EARLY TUE. THE
PRESENTATION OF THE UPPER TROUGH ON SATELLITE IMAGERY SUPPORTS
MODEL OUTPUT SHOWING THE TROUGH CUTTING OFF AN UPPER LOW N OF
PUERTO RICO AND THE USVI ALONG ROUGHLY 65W THROUGH MON. THIS
WILL SUPPORT DEVELOPMENT OF A TROUGH OVER THE EASTERN CARIBBEAN
EARLY IN THE WEEK. FRESH TO STRONG TRADE WINDS WILL PERSIST OVER
THE WATERS S OF 25N BETWEEN THE TROUGH IN THE CARIBBEAN AND A
REINFORCED SUBTROPICAL RIDGE N OF THE AREA.

WEAK LOW AMPLITUDE PERTURBATIONS ARE NOTED DEEP IN THE TROPICS
ALONG THE ITCZ W OF 45W. ONE OF THESE PRESENTS WELL ON A 1325
UTC ASCAT PASS...AND ALIGNS WELL WITH THE 12 UTC SOUNDING FROM
CAYENNE FRENCH GUIANA. THIS WEAK TROUGH/TROPICAL WAVE WILL START
TO AMPLIFY WITH THE UPPER LOW FORMING ALONG 65W...EVENTUALLY
FORMING THE AFOREMENTIONED TROUGH OVER THE EASTERN CARIBBEAN.

FARTHER EAST...BROAD 1029 MB SURFACE HIGH PRES CENTERED NEAR
35N39W DOMINATES THE CENTRAL TROPICAL ATLC...SUPPORTING A
MODERATE TO FRESH TRADE WINDS S OF 20N CONVERGING INTO THE ITCZ
W OF 35W. OFF THE COAST OF SENEGAL...THERE IS SOME INDICATION OF A
NORTHERN VORTEX THAT SHIFTED OFF THE COAST PREVIOUSLY...BUT
LITTLE CLEAR INDICATION OF AN ORGANIZED TROPICAL WAVE AT THIS
TIME IN PART DUE TO FAIRLY DRY CONDITIONS AND LACK OF SENSIBLE
WEATHER IN THE AREA. WILL MONITOR THIS FOR POSSIBLE TROPICAL WAVE
OVER THE NEXT COUPLE OF DAYS OVER THE FAR EASTERN ATLC.

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

$$
CHRISTENSEN


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