[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 142357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED MAR 14 2007

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N10W 2N20W 1N30W THEN DIPS ALONG
THE EQUATOR TO S AMERICA AT 50W. ITCZ REMAINS FAIRLY ACTIVE WITH
CLUSTERS OF SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120
NM EITHER SIDE OF THE AXIS BETWEEN 14W-20W. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS WITHIN 180 NM N OF THE
ITCZ W OF 34W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG SLOW MOVING CUT OFF LOW IS SITUATED N OF THE DISCUSSION
OVER NE TEXAS. THE LOW IS EMBEDDED WITHIN A DEEP LAYERED TROUGH
THAT EXTENDS FROM THE UPPER MID-WEST S THROUGH E TEXAS AND THE
FAR WRN GULF. MODERATE TO STRONG MID AND UPPER LEVEL SWLY WINDS
IN COMBINATION WITH DIFFLUENCE ALOFT ALONG WITH LOW-LEVEL MOIST
SE RETURN FLOW CONTINUE TO AID SCATTERED STRONG TSTMS ALONG THE
NRN GULF COAST W OF 84W. THESE STORMS ARE RAPIDLY MOVING E AND
WILL BE AFFECTING THE E PORTION  OF THE GULF TONIGHT INTO THU
MORNING. A SUBTROPICAL JET STREAM BRANCH DIVES SEWD INTO
WRN TEXAS AND ROUNDS THE SRN PERIPHERY OF THE UPPER LOW FROM
ROUGHLY 32N100W THROUGH 29N94W AND NEWD ACROSS SE LOUISIANA
AND SRN MISSISSIPPI. THIS JET IS TRANSPORTING/GENERATING A FAIR
AMOUNT OF UPPER LEVEL MOISTURE IN THE FORM OF HIGH CLOUDINESS
ACROSS THE GULF E OF 87W. MODERATE TO STRONG SUBSIDENCE AND
ASSOCIATED DRY AIR ALOFT IS PUNCHING INTO THE GULF BETWEEN
THE TROUGH AND A BROAD AREA OF HIGH LEVEL RIDGING THAT COVERS
THE SRN SECTOR S OF 24N. THIS DRY AIR WILL CONTINUE TO PUSH E
EVENTUALLY STABILIZING THE ENTIRE GULF. AT THE SFC...SLY RETURN
FLOW IN THE RANGE OF 20-25 KT IS NOW OCCURRING OVER THE NW
PART OF THE GULF IN ADVANCE OF THE ASSOCIATED LOW PRES AND
FRONTAL TROUGH MOVING EWD ACROSS TEXAS. WINDS ELSEWHERE ACROSS
THE GULF ARE E-SE IN THE RANGE OF 15-20 KT. EXPECT SLY RETURN
WINDS TO INCREASE ACROSS MUCH OF THE MIDDLE AND E GULF OVER
THROUGH FRI AS THE FRONTAL BOUNDARY MAKES IT WAY EWD ACROSS
THE GULF.

CARIBBEAN...
THE WRN PORTION OF THE AREA IS DOMINATED BY WLY UPPER LEVEL FLOW
ON THE NRN PERIPHERY OF AN UPPER HIGH CENTERED OVER COSTA RICA.
THE UPPER PATTERN THEN TRANSFORMS INTO A TROUGH ACROSS THE
ERN CARIB WITH THE AXIS ROUGHLY RUNNING FROM PUERTO RICO SW TO
VENEZUELA AND COLOMBIA. CONFLUENCE ALOFT BETWEEN THESE FEATURES
IS RESULTING IN MODERATE TO STRONG SUBSIDENCE AND ASSOCIATED
DRY AIR/STABILITY S OF 17N E OF 82W. MODESTLY DRY AIR ALOFT
COVERS THE REMAINDER OF THE BASIN. IN THE LOWER LEVELS...STRONG
SFC HIGH PRES LOCATED N OF THE REGION IS PRODUCING MODERATE TO
FRESH NE-ELY TRADES. THESE WINDS ARE IMPACTING UPON AN OLD
FRONTAL TROUGH THAT EXTENDS INTO THE EXTREME NE CARIBBEAN IN
THE VICINITY OF THE LEEWARD ISLANDS SW TO NEAR 16N67W. AS A
RESULT...PATCHES OF OVERCAST TO BROKEN LOW/MID CLOUDS WITH
EMBEDDED SCATTERED SHOWERS ARE OBSERVED GENERALLY FROM 14N-17N
E OF 74W. THE TROUGH IS FORECAST TO SLOWLY DISSIPATE THROUGH
THU. DOPPLER RADAR IMAGERY FROM THE SAN JUAN FORECAST OFFICE
SHOWS THAT ISOLATED SHOWERS MOVING SW ARE NOW MAINLY CONFINED TO
THE W PART OF PUERTO RICO...WITH SCATTERED SHOWERS ALSO MOVING
SW SEEN JUST SW OF THE WRN SIDE OF THE ISLAND. THESE SHOWERS
WILL DECREASE THROUGH THU NIGHT AS MOISTURE ASSOCIATED WITH
TROUGH DIMINISHES.

WESTERN ATLANTIC...
PROGRESSIVE PATTERN HERE IS DEPICTED BY A MID AND UPPER LEVEL
RIDGE/TROUGH NOTED W OF ABOUT 55W ON WATER VAPOR IMAGERY. RIDGING
IS PRESENT W OF 67W WITH ITS AXIS ALONG 76W. HIGH LEVEL MOISTURE
IN THE FORM OF HIGH CIRRUS CLOUDS ARE STREAMING FROM THE GULF
OF MEXICO EWD ACROSS THE FLORIDA PENINSULA AND INTO THE ATLC
REACHING TO 70W...THEN QUICKLY DRIES OUT E OF THERE WHERE
THE FLOW PATTERN BECOMES NW IN RESPONSE TO BROAD TROUGHING
ASSOCIATED WITH AN UPPER LEVEL LOW WELL N OF THE AREA. ABUNDANT
MODERATE TO STRONG SUBSIDENCE AND DRY AIR COVERS THE AREA
BETWEEN 50W-70W. AT THE SURFACE...A COLD FRONT ENTERS THE AREA
THROUGH 32N49W AND EXTENDS THROUGH 26N51W TO 23N55W WHERE IT
BECOMES A FRONTAL TROUGH SW TO THE LEEWARD ISLANDS. SCATTERED
SHOWERS AND TSTMS ARE NOTED WITHIN 180 NM AHEAD OF THE FRONT
N OF 25N...WHILE ISOLATED SHOWERS AND TSTMS ARE SEEN ELSEWHERE
WITHIN 90 NM EITHER SIDE OF FRONTAL TROUGH. THE FRONT IS
FORECAST TO MOVE VERY SLOW AND BECOME DIFFUSE THROUGH LATE
FRI NIGHT AS A RIDGE STRETCHES NE-SW THROUGH THE AREA BETWEEN
45W-70W.

EASTERN ATLANTIC...
A DEEP LAYER RIDGE COVERS THIS AREA BETWEEN 30W-55W WITH A RIDGE
AXIS EXTENDING FROM 32N37W SW THROUGH 22N43W TO NEAR 15N46W.
UPPER LEVEL DEBRIS MOISTURE FROM CONVECTION ASSOCIATED WITH
THE COLD FRONT DESCRIBED IN ABOVE PARAGRAPH IS ADVECTING
EWD ACROSS THE RIDGE TO 39W WHERE IT DRIES OUT IN AN AREA
OF MODERATE SUBSIDENCE. HERE...THE MID/UPPER LEVEL FLOW VEERS
NWLY IN RESPONSE TO A NEARLY STATIONARY SMALL STACKED LOW THAT
CONTINUES STACKED OVER THE CANARY ISLANDS. A MID/UPPER LEVEL
TROUGH EXTENDS FROM THIS LOW SW THROUGH 22N23W TO NEAR 10N34W.
THE SURFACE LOW IS ANALYZED WITH A PRES OF 1011 MB AT THE
SFC...AND IS FORECAST TO DISSIPATE WITHIN THE NEXT 24 HRS.
SCATTERED SHOWERS AND TSTMS ARE SEEN WITHIN 60 NM OF THE LOW
MAINLY IN THE SW QUADRANT. HIGH PRES RIDGE EXTENDS THROUGH
32N32W 23N39W. HIGH PRES COVERS THE PORTION OF THE AREA BETWEEN
21N-45W.

IN THE DEEP TROPICS...THE SRN PERIPHERY OF THE UPPER TROUGH
IS MEETS UP WITH A SUBTROPICAL JET STREAM BRANCH THAT EXTENDS
FROM 10N24W NEWD THROUGH 15N23W TO AND NE TO ACROSS AFRICA
NEAR 19N17W. THE JET STREAM BRANCH IS ATTENDED BY BROKEN TO
OVERCAST HIGH LEVEL MOISTURE WITHIN 300 NM TO ITS SE...AND
IS QUICKLY STREAMING NEWD ACROSS AFRICA. UPPER CONFLUENT FLOW
IS NOTED TO THE N OF THE JET STREAM W OF THE TROUGH. MID/UPPER
LEVEL RIDGING EXTENDS ALONG 4N/5N FROM BRAZIL E TO AFRICA. AN
UPPER LEVEL ANTICYCLONE IS NEAR 4N33W. THIS RIDGING IS HELPING
SUSTAIN CONVECTION ALONG THE ITCZ.

$$
AGUIRRE





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