[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131723
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU 13 JAN 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
1700 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 1N0 2N12W 3.5N23W 1N35W 6N53W 5N60W.
SCATTERED MODERATE CONVECTION WITHIN 100 NM OF THE AXIS BETWEEN
28W-40W. ISOLATED SHOWERS WITHIN 30 NM OF THE AXIS BETWEEN
45W-50W.

...DISCUSSION...

GULF OF MEXICO...
A COMPLEX FRONTAL SYSTEM IS MOVING E OF TEXAS INTO THE NW GULF
WITH POTENTIALLY SEVERE WEATHER EXTENDING SW OF THE LOUISIANA/
MISSISSIPPI COAST. THE MAIN COLD FRONT HAS BEEN ANALYZED FROM
ABOUT BEAUMONT TEXAS SWWD TO JUST PAST TAMPICO MEXICO BASED ON A
SHARP TEMPERATURE GRADIENT WHERE VALUES FALL FROM FROM THE LOWER
70S F TO THE MID/LOWER 50S OVER SE TEXAS. THE FRONT IS SURGING
DOWN THE E SLOPES OF THE SIERRA MADRE AND WINDS HAVE BEGUN
GUSTING OVER 30 KT AT TAMPICO WITH DUST/SAND IN THE
AIR...INDICATING THAT THE FRONT HAS PASSED. BROAD LOW PRES IS
LOCATED JUST E OF THE FRONT...WITH A 1006 MB LOW CENTERED NEAR
27N94W. A FAST-MOVING SQUALL LINE IS LOCATED ABOUT 250 NM AHEAD
OF THE FRONT...EXTENDING FROM NRN ALABAMA TO THE MISSISSIPPI
DELTA...BUT A CASE COULD BE MADE THAT THIS BOUNDARY IS ALSO A
FRONT SINCE TEMPERATURES FALL FROM NEAR 70 F TO THE MID 50S F
OVER LOUISIANA. THIS WHOLE SYSTEM IS BEING SUPPORTED BY A DEEP
UPPER LEVEL LONGWAVE TROF WHICH IS CENTERED OVER THE CNTRL
PLAINS EXTENDING SWD TO NW MEXICO. UPPER DIVERGENCE IS AHEAD OF
THE TROF SPREADING INTO THE TENNESSEE/OHIO VALLEYS WITH
SCATTERED MODERATE CONVECTION N OF 25N BETWEEN 90W-96W. DOPPLER
RADAR SHOWS THE LEADING EDGE OF THE SQUALL LINE MOVING THROUGH
NEW ORLEANS AS OF 1500Z WITH TRAILING MODERATE STRATIFORM RAIN
EXTENDING BACK TO THE LOUISIANA/TEXAS BORDER. A CLUSTER OF
SCATTERED MODERATE CONVECTION HAS ALSO DEVELOPED FROM 26N-30N
BETWEEN 85W-88W MOVING N TOWARDS THE FLORIDA PANHANDLE.
ELSEWHERE...A SECOND BUT DRIER UPPER TROF EXTENDS FROM THE BAY
OF CAMPECHE SWWD PAST THE GULF OF TEHUANTEPEC.

CARIBBEAN...
BROAD MID/UPPER LEVEL RIDGE IS TILTED BACKWARDS FROM NW
VENEZUELA OVER THE W CARIBBEAN TOWARDS CUBA...THEN SLOPES TO
MORE ZONAL FLOW OVER THE E CARIBBEAN AND LESSER ANTILLES. THE
FLOW IS SLIGHTLY DIFFLUENT EMERGING AWAY FROM CNTRL AMERICA
TOWARDS JAMAICA AND THIS IS PRODUCING AN AREA OF SCATTERED
MODERATE CONVECTION NEAR HONDURAS FROM 13N-19N BETWEEN 81W-85W.
THE MIDDLE AND UPPER ATMOSPHERE IS RATHER DRY HOWEVER...SO
ACTIVE WEATHER IS HARD TO COME BY OVER MUCH OF THE AREA. A FEW
SHOWERS ARE ORIENTED ALONG A LINE FROM MARGARITA ISLAND ACROSS
TRINIDAD/TOBAGO TO THE N OF GUYANA ALONG A LOW-LEVEL CONVERGENCE
LINE.

ATLANTIC OCEAN...
STRONG HIGH PRES IS CENTERED N OF THE AREA AND IS PRODUCING A
TIGHT PRES GRADIENT ACROSS THE ATLC OCEAN BETWEEN AFRICA AND THE
BAHAMAS...AND THE EASTERLY WINDS HAVE BEEN UP TO 30 KT AS
INDICATED BY QSCAT IMAGERY. IN THE UPPER LEVELS...A SMALL-SCALE
BUT AMPLIFIED RIDGE EXTENDS FROM THE NRN BAHAMAS NEWD PAST
32N73W AND IS KEEPING THE MID/UPPER LEVEL CLOUDS ASSOCIATED WITH
THE UPSTREAM GULF SYSTEM WELL TO THE N OF THE AREA. A SHORTWAVE
TROF IS DROPPING INTO THE AREA FROM 31N58W 26N70W BUT IS CAUSING
NO SIGNIFICANT WEATHER SAVE A FEW HIGH CLOUDS N OF 26N BETWEEN
36W-53W. THE FLOW IS MOSTLY ZONAL ELSEWHERE AND IS PRECLUDING
FRONTAL ACTIVITY FROM DROPPING INTO THE REGION. A WEAK COLD
FRONT IS HANGING UP ALONG 32N37W 30N48W BUT SHOULD WASH OUT AS
HIGH PRES ONCE AGAIN BUILDS FROM W TO E. FARTHER S...ASIDE FROM
ITCZ CONVECTION THERE IS A LARGE AREA OF ISOLATED SHOWERS E OF
THE LESSER ANTILLES FROM 6N-15N BETWEEN 48W-62W THAT CONTINUES
TO MOVE TO THE W. THE ATMOSPHERE DRIES OUT CONSIDERABLY E OF 38W
BEHIND A LOW-LEVEL DISTURBANCE...AND A PLUME OF SAHARAN DUST IS
OBSERVED EXTENDING UP TO 500 NM N OF THE ITCZ.

$$
BERG



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