[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 101753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI 10 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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
1730 UTC.

...SPECIAL FEATURE...

HURRICANE IVAN CENTERED NEAR 16.8N 75.8W OR ABOUT 85 MILES SSE
OF KINGSTON JAMAICA AT 10/1800 UTC MOVING WNW 10 KT. MAXIMUM
SUSTAINED WIND SPEED IS 125 KT WITH GUSTS TO 155 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE REPORTED FROM A RECONNAISSANCE AIRPLANE
IS 939 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC OR
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. THE EYE OF HURRICANE
IVAN BECAME VERY OBSCURED DURING THE EARLY MORNING HOURS BUT
OVER THE PAST FEW HOURS THE REPRESENTATION HAS IMPROVED
DRASTICALLY WITH CONVECTION WRAPPING TIGHTLY AROUND A NEW 10 NM
WIDE EYE. THE CONVECTION ITSELF HAS BECOME LESS LOPSIDED AND
MORE AXISYMMETRIC WITH WHITE BANDING EXTENDING ALL THE WAY
AROUND THE CENTER...AND CLOUD TOP TEMPERATURES AS COLD AS -80C
ALONG THE WRN EYEWALL. THESE CONDITIONS INDICATE THAT THE
HURRICANE PROBABLY WENT THROUGH AN EYEWALL REPLACEMENT CYCLE
DURING THE PAST 18 HRS OR SO. MICROWAVE IMAGERY...PRIMARILY
SSM/I AND TRMM...INDICATED ONE DISTINCT BUT NOT QUITE CLOSED
EYEWALL THIS MORNING WHEREAS YESTERDAY A DOUBLE EYEWALL
STRUCTURE WAS OBSERVED. UPPER LEVEL OUTFLOW IS EXCELLENT TO THE
N AND SW OF THE SYSTEM...WITH AN APPARENT OUTFLOW JET EXTENDING
EWD ACROSS E CUBA AND THE SRN BAHAMAS. SOME OF THE SPIRAL BANDS
HAVE ALREADY BEGUN SPREADING ACROSS JAMAICA...HISPANIOLA...AND
SE CUBA AND VERY HEAVY RAINFALL WILL CONTINUE TO BE A PROBLEM
ALONG WITH THE STRONG WINDS. SATELLITE RAINFALL IS ESTIMATING AN
ACCUMULATION OF 15"/380 MM OF RAIN NEAR THE CENTER OF THE TRACK
OF IVAN...AND THESE RAINFALL TOTALS COULD BE EVEN HIGHER IN THE
MOUNTAINOUS TERRAIN OF JAMAICA. NUMEROUS MODERATE/STRONG
CONVECTION WITHIN 120 NM OF THE CENTER OF IVAN. SCATTERED
MODERATE ELSEWHERE IN SPIRAL BANDS FROM 12.5N-20N BETWEEN
70W-80W.

...TROPICAL WAVES...

TROPICAL WAVE INTRODUCED BETWEEN AFRICA AND THE CAPE VERDE
ISLANDS ALONG 20W S OF 22N MOVING W 10-15 KT. THE BAMAKO
VERTICAL SOUNDING SHOWS A DISTINCT WAVE PASSAGE ABOUT 48 HRS
AGO...AND DAKAR HAS GONE FROM DEEP-LAYERED NELY FLOW TO
DEEP-LAYERED SELY FLOW OVER THE PAST 24 HRS. NOW A SHARP
CIRCULATION...PRIMARILY IN MID-LEVEL CLOUDS...IS OBSERVED OFF
THE COAST WITH MANY SFC OBSERVATIONS IN W AFRICA SHOWING SLY
FLOW BEHIND THE AXIS. SCATTERED MODERATE CONVECTION FROM 9N-13N
BETWEEN 20W-26W. DISSIPATING WIDELY SCATTERED SHOWERS/TSTMS OFF
THE COAST OF MAURITANIA AND WRN SAHARA FROM 18N-22N BETWEEN
16W-20W.

CENTRAL ATLC TROPICAL WAVE ALONG 39W/40W S OF 18N MOVING W 15-20
KT. THE WAVE HAS A BROAD AND LOW-AMPLITUDE SIGNATURE WITH
CONVECTION ALIGNED LINEARLY ACROSS THE WAVE AXIS. WIDELY
SCATTERED MODERATE CONVECTION...GENERALLY NEAR THE ITCZ...FROM
10N-15N BETWEEN 32W-46W.

TROPICAL WAVE LOCATED ABOUT 260 NM E OF THE LEEWARD/WINDWARD
ISLANDS ALONG 55W/56W S OF 21N MOVING W 15-20 KT. A 1011 MB LOW
HAS BEEN ANALYZED ALONG THE WAVE AXIS NEAR 14N56W BASED ON
SEVERAL SHIP OBSERVATIONS AND SOME TSTMS NEAR A WEAK LOW-LEVEL
CIRCULATION. THE NRN PART OF THE WAVE IS INTERACTING WITH A
SFC/UPPER LEVEL TROF TO ITS N AND IS ENHANCING TSTM COVERAGE.
DEVELOPING SCATTERED MODERATE CONVECTION NEAR THE LOW FROM
13N-15N BETWEEN 56W-59W.

TROPICAL WAVE ALONG 100W...NEAR ACAPULCO...HAS MOVED W OF THE
AREA.

...ITCZ...

ITCZ AXIS EXTENDS ACROSS W AFRICA TO THE MAURITANIA/WESTERN
SAHARA BORDER...THEN FARTHER S ALONG 12N22W 11N27W 12N38W 10N44W
17N54W...THEN ALONG 10N58W 7N80W. SCATTERED MODERATE CONVECTION
S OF THE AXIS FROM 5N-10N BETWEEN 22W-28W. WIDELY SCATTERED
MODERATE FROM 3N-6N BETWEEN 37W-42W. SCATTERED MODERATE 120 NM
NE OF THE AXIS BETWEEN 50W-54W.

...DISCUSSION...

GULF OF MEXICO...
SPOTTY SHOWERS AND TSTMS CONTINUE TO DEVELOP ACROSS PARTS OF THE
E AND SW GULF DUE TO A SFC TROF DRAPED ACROSS THE AREA AND A
FRONTAL BOUNDARY WHICH HAS SAGGED ACROSS THE N GULF WATERS. THE
SFC TROF EXTENDS FROM 30N82W IN N FLORIDA SW TO 20N95W IN THE
BAY OF CAMPECHE WITH WIDELY SCATTERED SHOWERS/TSTMS FROM 21N-30N
BETWEEN 82W-86W AND FROM 18N-23N BETWEEN 89W-97W. THE FRONTAL
BOUNDARY...NOW STATIONARY...IS QUICKLY WEAKENING ALONG 31N84W
27N97W WITH A DRIER AIR MASS TO THE N NOT REALLY BEING ABLE TO
SPREAD ANY FARTHER S. THE FRONT IS ASSOCIATED WITH A MID/UPPER
LEVEL SHORTWAVE EXTENDING SW OF THE LOUISIANA COAST BUT THIS
FEATURE HAS BEEN STOPPED IN ITS TRACKS BY A FAIRLY STRONG UPPER
LEVEL RIDGE ACROSS CNTRL FLORIDA AND THE E GULF. MUCH DRIER AIR
HAS FILTERED ACROSS THE NW GULF NEAR THE TROF...BUT THIS TOO HAS
BEEN STOPPED IN ITS TRACKS WITH ABUNDANT MOISTURE HOLDING ITS
OWN ACROSS THE SE HALF OF THE AREA.

CARIBBEAN...
OF COURSE...THE MAJOR FEATURE OF THE DAY IS HURRICANE IVAN...
WHICH IS SOON TO BE BATTERING THE ISLANDS OF JAMAICA...
HISPANIOLA...AND SE CUBA WITH EXTREMELY STRONG WINDS AND
FLOODING RAINFALL. THE REST OF THE CARIBBEAN IS UNDER MUCH NICER
WEATHER AROUND THE PERIPHERY OF IVAN...WITH MODERATE/STRONG
SUBSIDENCE EXTENDING ACROSS THE LEEWARD/WINDWARD ISLANDS S OF
ABOUT ANTIGUA AND ALSO ACROSS THE GULF OF HONDURAS AND OFF THE
YUCATAN COAST. UPPER LEVEL OUTFLOW IS SPREADING HIGH LEVEL
CLOUDINESS WWD TO ABOUT 82W...EWD TO 66W...AND NWD INTO THE SW
ATLC. ASIDE FROM THE HURRICANE...THE ONLY OTHER SIGNIFICANT
CONVECTION IS WIDELY SCATTERED SHOWERS ABOUT 60 NM N OF THE
PANAMANIAN COAST.

SUBTROPICAL ATLANTIC...
TWO SEPARATE MID/UPPER LOWS ARE RULING THE AREA W OF 50W BUT
EACH IS CAUSING DRASTICALLY DIFFERENT WEATHER. THE WESTERNMOST
LOW IS LOCATED ABOUT 160 NM NE OF THE CNTRL BAHAMAS AND IS
DRIFTING SLOWLY TO THE W...WITH MOSTLY MODERATE/STRONG
SUBSIDENCE N OF 25N W OF 60W. THE AREA IS ADJACENT TO AN
IMPRESSIVE OUTFLOW JET OF HURRICANE IVAN WHICH EXTENDS E OF THE
SRN BAHAMAS...WITH CIMSS VECTORS INDICATING UPWARDS OF 70-80 KT
AWAY FROM THE STORM. THE SECOND MID/UPPER LOW IS A LITTLE MORE
COMPLEX AND ACTUALLY SEEMS TO BE TWO LOWS...NEAR 25N57W AND
31N59W...ROTATING AROUND A COMMON POINT. STRONG DIFFLUENCE TO
THE E OF THIS COMPLEX HAS INITIATED SCATTERED MODERATE/STRONG
CONVECTION FROM 20N-30N BETWEEN 49W-55W AND MORE ISOLATED
SHOWERS/TSTMS FROM 26N-30N BETWEEN 55W-65W. ELSEWHERE E OF
50W...THE FLOW IS PRIMARILY WLY TO 30W WITH A SHORTWAVE TROF
EXTENDING SWD ALONG 32N33W 25N30W. NARROW RIDGING HAS BUILT IN
AHEAD OF THE TROF FROM THE CAPE VERDES NEWD PAST THE CANARY
ISLANDS.

TROPICAL ATLANTIC...
THE UPPER LEVEL FLOW OVER THE TROPICS IS DOMINATED BY AN
EXPANSIVE UPPER LEVEL HIGH BETWEEN 30W AND 55W...CENTERED NEAR
17N43W. THERE APPEARS TO BE SOME SORT OF SPEED DIVERGENCE AXIS
ALONG 16N46W 11N30W WITH THE NELY FLOW ACCELERATING TOWARDS THE
EQUATOR...AND THIS HAS ENHANCED CONVECTIVE ACTIVITY NEAR THE
ITCZ BETWEEN 32W-47W. E OF 30W...A DRY TONGUE OF AIR EXTENDS
ACROSS THE CAPE VERDE ISLANDS N OF 13N BETWEEN 21W-32W IN
ASSOCIATION WITH THE SHORTWAVE TROF N OF THE AREA...BUT A SURGE
OF MOISTURE IS NOW BEGINNING TO SPREAD IN FROM THE SE. WIDELY
SCATTERED SHOWERS/TSTMS ARE POPPING WITHIN THIS MOIST
AIR...ENHANCED BY A SECOND BUT WEAKER AREA OF UPPER LEVEL SPEED
DIVERGENCE AND FOCUSED ALONG A TROPICAL WAVE WHICH RECENTLY
MOVED OFF THE AFRICAN COAST.

$$
BERG


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