[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 061721
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN 06 FEB 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
1645 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N0 3N10W 3.5N18W 2N26W 4N38W 1N51W.
A LARGE TROPICAL SQUALL LINE/MCC IS MOVING W ACROSS THE PRIME
MERIDIAN WITH NUMEROUS STRONG CONVECTION S OF 7N E OF 2.5W.
SCATTERED MODERATE UP TO 175 NM N OF THE AXIS BETWEEN 5W-20W.
SCATTERED MODERATE WITHIN 150 NM OF THE AXIS BETWEEN 20W-36W.

...DISCUSSION...

MEXICO AND GULF OF MEXICO...
A BROAD AND DEEP LONGWAVE TROF IS LOCATED OVER THE WESTERN U.S.
AND PACIFIC COAST OF MEXICO AND THERE ARE SEVERAL SHORTWAVE
DISTURBANCES WHICH ARE MOVING UP THE E SIDE THROUGH MEXICO AND
THE CNTRL PLAINS. THERE IS A 90-110 KT JET WHICH EXTENDS ACROSS
N MEXICO TOWARDS E OKLAHOMA/W ARKANSAS WITH A 400 NM WIDE BAND
OF HIGH CLOUDS TO THE E OF THE AXIS (GENERALLY E OF 100W).
HOWEVER...A STRONG UPPER RIDGE EXTENDING FROM THE YUCATAN
CHANNEL NWD TOWARDS THE FL PANHANDLE AND GEORGIA IS HOLDING ITS
OWN AND IS KEEPING THE RAIN SHIELD WELL INLAND OVER THE CNTRL
PLAINS. ONLY PATCHY LOW CLOUDS REMAIN TRAPPED IN SOME OF THE
MEXICAN VALLEYS WHILE A FEW STRATOCU ARE MOVING NWWD OVER THE
GULF WATERS WITHIN THE RETURN FLOW. THE CLOUD DECK THICKENS NEAR
THE TX COAST WITH A FEW TRAILING SHOWERS SKIRTING THE COASTAL
WATERS. A WEAK COLD FRONT IS EXPECTED TO STALL AND DISSIPATE
ALONG THE TX/LA COAST LATE MON AND TUE INCREASING RAIN
CHANCES...AND THEN A STRONGER SECOND COLD FRONT WILL PUSH INTO
THE GULF LATE WED AND THU BUT WITH A MORE LIMITED MOISTURE
SUPPLY.

WEST/CENTRAL ATLANTIC...
A 1003 MB OCCLUDED LOW HAS REMAINED NEARLY STATIONARY FOR ALMOST
A WEEK NOW AND IS CURRENTLY LOCATED ABOUT 220 NM SE OF BERMUDA
NEAR 29N62.5W. THE OCCLUDED FRONT CURVES N THEN E AROUND THE LOW
ALONG 28N64W 31N62W 31N56W 25N55W THEN CONTINUES AS A
DISSIPATING COLD FRONT TO THE VIRGIN ISLANDS/PUERTO RICO. THE
SFC LOW IS DEEP-LAYERED AND BROAD CYCLONIC FLOW IN THE MID/UPPER
LEVELS EXTENDS ACROSS THE ENTIRE W/CNTRL ATLC...GENERALLY W OF
50W. BANDS OF CONVECTION HAVE BEEN DEVELOPING ALONG THE FRONT
AND THEN ARE BEING FLUNG TO THE E...WITH A BAND OF SCATTERED
MODERATE CONVECTION CURRENTLY BETWEEN 150W-350W E AND N OF THE
OCCLUDED FRONT. NEWLY-DEVELOPING CONVECTION IS NOW FORMING
WITHIN 150 NM E OF THE FRONT...ESSENTIALLY REPLACING THE
STRONGER EWD-MOVING CONVECTION. IN ADDITION...AN OLD FRONTAL
TROF IS LOCATED ABOUT 250 NM SE OF THE COLD FRONT...STRETCHING
NE OF DOMINICA...AND NUMEROUS MODERATE/STRONG CONVECTION HAS
BEEN FOCUSED NEAR THE AREA OF STRONGEST LOW-LEVEL CONVERGENCE
FROM 20N-26N BETWEEN 45W-52W. STRONG SUBSIDENCE IS IN THE
MID/UPPER LEVELS OF THE ATMOSPHERE BEHIND THE COLD FRONT BUT
THERE IS ENOUGH COLD AIR ALOFT TO SUPPORT ISOLATED SHOWERS/TSTMS
IN THE VICINITY OF THE LOW FROM 26N-31N BETWEEN 57W-65W. IT DOES
APPEAR THAT THE LOW WILL HANG AROUND FOR ANOTHER 48 HRS OR
SO...BUT IT SHOULD THEN BEGIN TO LIFT N OF THE AREA BY WED AND
THU.

CARIBBEAN...
THE WEAKENING COLD FRONT ASSOCIATED WITH THE LARGE OCCLUDED LOW
OVER THE W ATLC HAS PROGRESSED SWD TO THE NRN LEEWARD ISLANDS
AND PUERTO RICO/VIRGIN ISLANDS. RADAR IMAGERY FROM SAN JUAN
INDICATES THERE ARE SCATTERED LIGHT SHOWERS EMBEDDED WITHIN THE
90 NM WIDE FRONTAL CLOUD BAND...MANY OF WHICH ARE MOVING SE AWAY
FROM PUERTO RICO TOWARDS THE VIRGIN ISLANDS. AN OLD FRONTAL TROF
ALSO EXTENDS SE OF THE FRONT FROM NEAR ARUBA TO DOMINICA BUT THE
MID/UPPER LEVELS ARE TOO DRY TO SUPPORT ANY DEEP CONVECTION. A
STRONG UPPER RIDGE IS LOCATED OVER THE CNTRL AMERICAN LANDMASS
AND THE FLOW TO THE E OF THIS FEATURE IS CONVERGING WITH THE
BROAD CYCLONIC FLOW OVER THE W ATLC...PRODUCING A SWATH OF
STRONG SUBSIDENCE E/W ACROSS THE ENTIRE CARIBBEAN.
ELSEWHERE...PATCHY LOW CLOUDS EXTEND ACROSS THE NW CARIBBEAN
WITH A WEAK LINE OF SHOWERS MOVING SWWD TO THE GULF OF HONDURAS.

EAST ATLANTIC...
A STRONG SFC RIDGE EXTENDS NE/SW ACROSS THE AREA FROM MADEIRA
ISLAND TO NEAR 20N40W AND IS ADVECTING FEW/BROKEN STRATOCU OVER
THE E ATLC WATERS. A STRONG RIDGE IS ALSO LOCATED IN THE UPPER
LEVELS ALONG 37W/38W AND IS KEEPING VIRTUALLY ALL CONVECTION
ASSOCIATED WITH THE W ATLC LOW W OF 40W. FARTHER E...A LARGE
UPPER LEVEL LONGWAVE TROF EXTENDS SW OF PORTUGAL/SPAIN AND
REACHES ACROSS THE CANARY ISLANDS TO THE CAPE VERDES.
HOWEVER...THERE IS LITTLE ATMOSPHERIC MOISTURE TO WORK WITH AND
NO LIFTING MECHANISM TO SUPPORT DEEP CONVECTION. CONVECTION HAS
FORMED WITHIN A NARROW ZONE ALONG THE ITCZ E OF 40W PRIMARILY
DUE TO PERTURBED UPPER LEVEL WLY FLOW WHICH IS PRODUCING AREAS
OF DIVERGENCE. AN UPPER LEVEL ANTICYCLONE CENTERED S OF THE
EQUATOR NEAR 3S9W HAS BEEN PUSHING THE ITCZ CONVECTION NWD JUST
OFF THE AFRICAN COAST BUT DRY SAHARAN AIR RUNNING IN A BAND
BETWEEN 4N-14N IS LIMITING THE COVERAGE.

$$
BERG


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