[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE OCT 22 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL STORM LORENZO AT 22/2100 UTC IS NEAR
29.4N 51.2W. LORENZO IS MOVING EAST AT 7 KNOTS. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1003 MB. THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 45 KNOTS WITH GUSTS TO 55 KNOTS. PUBLIC ADVISORIES ON
LORENZO ARE ISSUED UNDER WMO HEADER WTNT33 KNHC AND UNDER AWIPS
HEADER MIATCPAT3. FORECAST/ADVISORIES ON LORENZO ARE ISSUED
UNDER WMO HEADER WTNT23 KNHC AND UNDER AWIPS HEADER MIATCMAT3.
NUMEROUS STRONG CONVECTION IS FROM 28N-31N BETWEEN 49W-51W.
SCATTERED MODERATE CONVECTION IS ELSEWHERE FROM 27N-32N BETWEEN
48W-52W.

...TROPICAL WAVES...
A TROPICAL WAVE EMERGED FROM THE WEST AFRICAN COAST EARLIER
TODAY. CURRENTLY ITS AXIS EXTENDS FROM 14N22W TO 06N23W AND IS
MOVING WEST AT APPROXIMATELY 10 KT. SSMI TOTAL PRECIPITABLE
WATER IMAGERY INDICATE THE WAVE IS MOSTLY EMBEDDED WITHIN A
MODERATE MOIST ENVIRONMENT WITH VERY DRY AIR ENGULFING THE
NORTHERN SECTOR OF THE WAVE. BOTH DRY AIR AND STRONG DEEP LAYER
WESTERLY WIND SHEAR ARE HINDERING DEEP CONVECTION AT THE TIME.
SCATTERED SHOWERS ASSOCIATED WITH THE MONSOON TROUGH CONVECTION
ARE IN THE SOUTHERN SECTOR OF THE WAVE S OF 09N WITHIN 140 NM
EITHER SIDE OF THE AXIS.

TROPICAL WAVE AXIS EXTENDS FROM 15N48W TO 07N48W AND IS MOVING
WEST AT ABOUT 10-15 KT. SSMI TOTAL PRECIPITABLE WATER IMAGERY
INDICATE THE WAVE IS MOSTLY EMBEDDED WITHIN A MODERATE MOIST
ENVIRONMENT WITH HIGHER VALUES EAST OF THE WAVE AXIS. THIS WAVE
LIES WITHIN THE BASE OF A TILTED UPPER-LEVEL TROUGH WHICH IS
SUPPORTING SCATTTERED MODERATE CONVECTION FROM 08N-15N BETWEEN
42W-49W.

TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS EXTENDING
FROM EASTERN CUBA NEAR 21N76W...ACROSS CENTRAL JAMAICA TO
CENTRAL PANAMA NEAR 10N79W. THE AXIS IS MOVING W-NW NEAR 10-15
KT. SSMI TOTAL PRECIPITABLE WATER IMAGERY INDICATE THAT N OF 16N
THE WAVE IS GENERALLY EMBEDDED WITHIN A DRY ENVIRONMENT WHILE
HIGH MOISTURE IS PRESENT IN THE SOUTHERN SECTOR OF IT. SCATTERED
MODERATE CONVECTION AND ISOLATED TSTMS MOSTLY ASSOCIATED WITH
THE MONSOON TROUGH AND BEING SUPPORTED BY UPPER-LEVEL DIVERGENCE
ARE S OF 15N WEST OF THE WAVE AXIS. ISOLATED SHOWERS AND TSTMS
ARE WITHIN 50 NM EAST OF THE AXIS FROM 17N-20N.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH THE WEST AFRICAN COAST NEAR
11N16W TO 08N23W TO 06N32W. THE ITCZ CONTINUES FROM 06N32W TO
05N40W TO 07N45W. BESIDES THE CONVECTION ASSOCIATED WITH THE
TRPCL WAVES...SCATTERED MODERATE CONVECTION IS FROM 01N-08N
BETWEEN 17W-30W. SIMILAR CONVECTION IS FROM 07N-10N BETWEEN 32W-
36W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM THE
UPPER GREAT LAKES TO THE CENTRAL GULF SUPPORTS A PAIR OF FRONTAL
BOUNDARIES. THE FIRST FRONTAL BOUNDARY IS A STATIONARY FRONT
THAT EXTENDS ACROSS NORTH-CENTRAL FLORIDA TO 29N82W SW TO 26N90W
TO 19N96W. A SECOND STATIONARY FRONT ENTERS THE NE BASIN THROUGH
PENSACOLA AND EXTENDS TO 28N87W WHERE IT TRANSITIONS TO A COLD
FRONT TO 27N93W 25N97W. WATER VAPOR IMAGERY SHOW THAT DIVERGENT
FLOW ASSOCIATED WITH HURRICANE RAYMOND IN THE EAST PACIFIC IS
ADVECTING MOISTURE TO THE CENTRAL GULF...WHICH IS SUPPORTING A
SWATH OF SHOWERS AND ISOLATED TSMS EAST OF A LINE FROM 30N86W TO
24N97W AND WEST OF A LINE FROM 27N82W TO 21N86W.

WITHIN THE NEXT 24 HOURS...THE COLD FRONT WILL OVERTAKE THE
STATIONARY FRONT AND WILL DRIFT E-SE TO EXTEND ACROSS CENTRAL
FLORIDA SW TO THE BAY OF CAMPECHE. THE COLD FRONT WILL MOVE
ACROSS SOUTHERN FLORIDA EARLY ON THURSDAY AND IS EXPECTED TO
MOVE OUT OF THE BASIN DURING THE NIGHT HOURS THAT DAY.

THE CARIBBEAN SEA...
A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
EXTENDING FROM EASTERN CUBA NEAR 21N76W...ACROSS CENTRAL JAMAICA
TO CENTRAL PANAMA NEAR 10N79W. SSMI TOTAL PRECIPITABLE WATER
IMAGERY INDICATE THAT N OF 16N THE WAVE IS GENERALLY EMBEDDED
WITHIN A DRY ENVIRONMENT WHILE HIGH MOISTURE IS PRESENT IN THE
SOUTHERN SECTOR OF IT. SCATTERED MODERATE CONVECTION AND
ISOLATED TSTMS MOSTLY ASSOCIATED WITH THE MONSOON TROUGH AND
BEING SUPPORTED BY UPPER-LEVEL DIVERGENCE ARE S OF 15N WEST OF
THE WAVE AXIS. ISOLATED SHOWERS AND TSTMS ARE WITHIN 50 NM EAST
OF THE AXIS FROM 17N-20N. IN THE WESTERN BASIN...MIDDLE TO UPPER
LEVEL RIDGING AND DRY AIR SUBSIDENCE DOMINATE TO SUPPORT FAIR
WEATHER TONIGHT. A MIDDLE TO UPPER LEVEL ELONGATED LOW EXTENDS
FROM THE SOUTHERN BAHAMAS TO THE CENTRAL CARIBBEAN SUPPORTING A
SURFACE TROUGH THAT MOVES ACROSS HISPANIOLA FROM 23N67W TO
18N72W. THIS INSTABILITY IN THE ATMOSPHERE IS RESPONSIBLE FOR
HEAVY SHOWERS AND TSTMS ACROSS THE ISLAND AND ADJACENT
WATERS...INCLUDING THE WINDWARD PASSAGE. MIDDLE TO UPPER LEVEL
WIND FLOW AROUND THE EASTERN PERIPHERY OF A RIDGE CENTERED IN
THE SW N ATLC IS ADVECTING MOISTURE TO THE SE CARIBBEAN TO
SUPPORT RAINSHOWERS IN THE WINDWARD ISLANDS.

THE TRPCL WAVE WILL CONTINUE TO DRIFT WESTWARD AND IS EXPECTED
TO BE NEAR 80W ON WEDNESDAY AFTERNOON...MOVING ACROSS CENTRAL
AMERICA AT NIGHT THE SAME DAY. A COLD FRONT IS EXPECTED TO ENTER
THE NW CARIBBEAN BASIN BY THURSDAY AFTERNOON.

HISPANIOLA...
A MIDDLE TO UPPER LEVEL ELONGATED LOW EXTENDS FROM THE SOUTHERN
BAHAMAS TO THE CENTRAL CARIBBEAN SUPPORTING A SURFACE TROUGH
THAT MOVES ACROSS HISPANIOLA FROM 23N67W TO 18N72W. THIS
INSTABILITY IN THE ATMOSPHERE IS RESPONSIBLE FOR HEAVY SHOWERS
AND TSTMS ACROSS THE ISLAND AND ADJACENT WATERS...INCLUDING THE
WINDWARD PASSAGE. SHOWERS WILL CONTINUE TO AFFECT THE ISLAND AND
ADJACENT WATERS THROUGH WEDNESDAY NIGHT. THESE SHOWERS WILL
SLOWLY DISPLACE W-NW THROUGH TIME AS THE UPPER-LEVEL LOW DRIFTS
IN THAT DIRECTION. A DRY AIRMASS IS EXPECTED TO ENTER THE
DOMINICAN REPUBLIC BY EARLY THURSDAY WHICH WILL LIKELY HELP TO
SUPPRESS CONVECTIVE ACTIVITY.

THE ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM THE
UPPER GREAT LAKES TO THE CENTRAL GULF SUPPORTS A STATIONARY
FRONT THAT ENTERS THE SW N ATCL NEAR 30N79W SW TO
29N81W...THROUGH NORTH-CENTRAL FLORIDA AND THE GULF. ISOLATED
SHOWERS AND TSTMS ARE WITHIN 100 NM EITHER SIDE OF THE FRONT IN
THE SW N ATCL. A MIDDLE TO UPPER LEVEL ELONGATED LOW EXTENDS
FROM THE SOUTHERN BAHAMAS TO THE CENTRAL CARIBBEAN SUPPORTING A
SURFACE TROUGH THAT MOVES FROM 23N67W...ACROSS HISPANIOLA TO
18N72W. SCATTERED MODERATE CONVECTION AND TSTMS EXTEND WITHIN 60
NM OFF THE NORTHERN COAST OF HAITI WHILE ISOLATED SHOWERS ARE
WITHIN 50 NM EITHER SIDE OF THE TROUGH AXIS. TROPICAL STORM
LORENZO IS IN THE CENTRAL ATLC. SEE THE SPECIAL FEATURES SECTION
ABOVE FOR MORE INFORMATION. FURTHER EAST...SE OF LORENZO...A
1019 MB HIGH PRESSURE CENTER IS NEAR 26N40W...WHICH IS EXPECTED
TO REMAIN STATIONARY WITHIN THE NEXT 24 HOURS. OVER THE EASTERN
BASIN...A DISSIPATING COLD FRONT EXTENDS FROM 30N18W SW TO
28N29W WITH NO CONVECTION ASSOCIATED WITH IT.

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

$$
NR

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