[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171143
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 17 2011

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...ITCZ/MONSOON TROUGH...

THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N11W TO
06N29W TO 05N39W TO 06N54W. WIDELY SCATTERED MODERATE CONVECTION
IS FROM 04N-08N BETWEEN 23W-43W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE REMAINS ANCHORED IN THE WESTERN CARIBBEAN
SEA AND EXTENDS NORTHWARD CONTINUING TO IMPACT MUCH OF THE
EASTERN GULF AND FLORIDA PENINSULA THIS MORNING. HOWEVER...A
WEAK MIDDLE TO UPPER LEVEL SHORTWAVE MOVING ACROSS THE CREST OF
THE RIDGE OVER THE SE CONUS SUPPORTS A COLD FRONT ANALYZED INTO
THE GULF NEAR 30N87W THEN SW TO 28N93W BECOMING STATIONARY ALONG
26N95W TO 22N96W AND INLAND OVER EAST-CENTRAL MEXICO. A FEW
ISOLATED SHOWERS ARE NOTED ON MOSAIC DOPPLER RADAR IMAGERY
WITHIN 60 NM EITHER SIDE OF THE FRONT...HOWEVER THE MAIN IMPACT
WITH THE FRONT IS INCREASED NORTHERLY WINDS IN THE RANGE OF 15
TO 20 KT AND MOSTLY OVERCAST SKIES. THE FRONT IS FORECAST TO
REMAIN STATIONARY TODAY AND DISSIPATE FURTHER OVER THE DURATION
OF THE WEEKEND. AS THE FRONT DISSIPATES...SURFACE HIGH PRESSURE
WILL BUILD ACROSS THE GULF THROUGH THE REMAINDER OF THE WEEKEND
WITH NORTHEASTERLY WINDS PERSISTING THROUGH SUNDAY NIGHT. BY
MONDAY...SOUTHERLY RETURN FLOW IS EXPECTED TO RE-ESTABLISH OVER
PORTIONS OF THE WESTERN GULF AS A AREA OF LOW PRESSURE DEVELOPS
OVER NORTH TEXAS AND OKLAHOMA.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION INFLUENCES MUCH OF THE
WESTERN CARIBBEAN CENTERED NEAR 16N80W WITH AXIS EXTENDING
NORTHWARD ALONG 80W. ON THE SOUTHERN PERIPHERY OF THE RIDGE...
S-SE DIFFLUENT FLOW ALOFT CONTINUES TO ENHANCE SCATTERED SHOWERS
AND TSTMS S OF 16N BETWEEN 76W-83W. MOST OF THIS CONVECTIVE
ACTIVITY IS FOCUSED NORTH OF THE MONSOON TROUGH AXIS EXTENDING
FROM THE E PACIFIC ALONG 09N TO NORTHERN COLOMBIA. OTHERWISE THE
REMAINDER OF THE WESTERN CARIBBEAN W OF 70W IS UNDER STRONG NE
TRADES DUE TO AN INCREASED PRESSURE GRADIENT FROM A 1023 MB HIGH
CENTERED OVER THE SW NORTH ATLC. FARTHER EAST...A VERY DRY AND
STABLE ATMOSPHERE IS NOTED UNDER NW FLOW ALOFT ON THE
SOUTHWESTERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED NEAR
27N50W AND ASSOCIATED TROUGHING E OF 70W. HOWEVER...A SHEAR LINE
EXTENDS ACROSS THE SE CARIBBEAN FROM 12N60W TO 12N72W WITH
WIDELY SCATTERED LOW-TOPPED SHOWERS OCCURRING WITHIN 90 NM
EITHER SIDE OF THE BOUNDARY AS IT CONTINUES TO BECOME MORE
DIFFUSE. EARLIER ASCAT PASSES AROUND 17/0110 UTC AND 17/0252 UTC
INDICATED STRONG NE WINDS WERE OCCURRING IN WAKE OF THE SHEAR
LINE AXIS ACROSS MUCH OF THE EASTERN AND CENTRAL CARIBBEAN
BETWEEN 62W-77W IN THE RANGE OF 20 TO 25 KT. A SECONDARY AREA OF
LOW-LEVEL MOISTURE CONVERGENCE EMBEDDED WITHIN THE STRONGER NE
TRADES IS GENERATING ISOLATED SHOWERS N OF 15N E OF 70W...
INCLUDING PUERTO RICO...THE US/UK VIRGIN ISLANDS...AND LEEWARD
ISLANDS. HIGH PRESSURE IS FORECAST TO REMAIN ANCHORED NE OF THE
BAHAMAS THROUGH THE REMAINDER OF THE WEEKEND MAINTAINING THE
AREA OF INCREASED E-NE TRADES.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE ANCHORED IN THE WESTERN CARIBBEAN SEA
CONTINUES TO INFLUENCE THE SW NORTH ATLC W OF 60W. A MOSTLY DRY
AND STABLE AIRMASS IS ASSOCIATED WITH THIS UPPER LEVEL FEATURE
AND CONTINUES TO SUPPORT A 1023 MB SURFACE HIGH CENTERED NEAR
29N71W. WINDS HAVE GENERALLY BECOME LIGHT NEAR THE HIGH CENTER
AND TO THE E OF 62W. A FEW FAST-MOVING ISOLATED SHOWERS ARE
STILL POSSIBLE WITHIN THE SCATTERED TO BROKEN STRATOCUMULUS
CLOUDS THIS MORNING GENERALLY S OF 30N W OF 56W. FARTHER EAST...
AN UPPER LEVEL LOW CENTERED NEAR 27N50W SUPPORTS A COMPLEX AREA
OF LOW PRESSURE ACROSS THE CENTRAL ATLC FOCUSED ON A NEARLY
STATIONARY 1007 MB LOW NEAR 26N50W. A PAIR OF COLD FRONTS STEM
FROM THE LOW...WITH THE PRIMARY FRONT SLOWLY DISSIPATING FROM
29N48W TO 24N46W TO 16N50W TO 14N55W WHERE IT TRANSITIONS TO A
SHEAR LINE TO 12N62W. A SECONDARY COLD FRONT IS ANALYZED FROM
THE LOW SW TO 18N56W. A PRE-FRONTAL TROUGH IS LOCATED EAST OF
THE PRIMARY FRONT ALONG 10N52W TO 18N48W. LOW-LEVEL CONVERGENCE
EAST OF THE SURFACE TROUGH AND FRONT ALONG WITH STRONG MIDDLE TO
UPPER LEVEL DIFFLUENCE IS GENERATING A BROAD AREA OF SCATTERED
SHOWERS AND ISOLATED TSTMS FROM 10N-32N BETWEEN 40W-48W. A FEW
ISOLATED SHOWERS ARE ALSO OCCURRING IN THE VICINITY OF THE LOW
CENTER FROM 24N-29N BETWEEN 48W-54W IN ASSOCIATION WITH THE
MIDDLE TO UPPER LEVEL LOW. THE REMAINDER OF THE EASTERN ATLC IS
UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1033 MB
HIGH CENTERED SE OF THE AZORES NEAR 36N23W. THE RIDGE AXIS
EXTENDS SW FROM THE HIGH TO 20N40W.

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

$$
HUFFMAN





This weather bulletin was brought to you by:
www.nashvilleweather.net