[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED OCT 15 2008

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

AT 15/1800 UTC...HURRICANE OMAR IS LOCATED BY AN AIR FORCE
RESERVE UNIT HURRICANE HUNTER AIRCRAFT NEAR 15.3N 66.6W AT
15/1800 UTC OR ABOUT 205 NM...380 KM...SOUTHWEST OF ST. CROIX
AND ABOUT 205 NM...375 KM...SOUTH-SOUTHWEST OF SAN JUAN PUERTO
RICO MOVING E-NE AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS
982 MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90
KT. PLEASE SEE LATEST NHC PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT5/WTNT35 KNHC AND THE FULL FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS.
NUMEROUS STRONG CONVECTION IS WITHIN 100 NM OF THE CENTER WITH
OUTER RAINBANDS AFFECTING THE ABC ISLANDS AND THE NE CARIBBEAN.
ONCE AGAIN...CURACAO REPORTED THIS MORNING 1.43 INCHES OF RAIN
IN 24 HOURS. THE SAN JUAN DOPPLER RADAR IS ALREADY SHOWING THE
EYE OF OMAR WITH NUMEROUS SHOWERS AND ISOLATED TSTMS OVER THE
VIRGIN ISLANDS AND THE E AND SE PORTION OF PUERTO RICO. OMAR IS
FORECAST TO MOVE THROUGH THE NORTHERN LEEWARD ISLANDS LATE
TONIGHT AND EARLY THURSDAY LIKELY AS A CAT 2 HURRICANE ON THE
SAFFIR-SIMPSON SCALE. IT ALSO ISN'T OUT OF THE QUESTION THAT
OMAR COULD ACHIEVE MAJOR HURRICANE STATUS JUST BEFORE THE
CYCLONE REACHES THE NORTHERN LEEWARD ISLANDS DUE TO THE CYCLONE
IS IN A RELATIVELY LOW SHEAR ENVIRONMENT AND OVER 29C AND WARMER
SEA SURFACE TEMPERATURES. STRONGER WINDS...ESPECIALLY IN GUSTS
...ARE LIKELY OVER ELEVATED TERRAIN. A HURRICANE WARNING COULD
BE REQUIRED FOR PUERTO RICO LATER TODAY.

LATEST VIS SATELLITE IMAGERY INDICATES THAT T.D. SIXTEEN HAS
MADE LANDFALL OVER NE HONDURAS LATE THIS MORNING. TROPICAL
DEPRESSION SIXTEEN IS CENTERED NEAR 15.8N AND 84.5W AT 15/1800
UTC OR ABOUT     MOVING W AT 4 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH
GUSTS TO 35 KT. PLEASE SEE LATEST NHC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE FULL
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE OVER THE SW AND NW CARIBBEAN FROM 10N-16N BETWEEN
77W-82W...AND FROM NORTHERN HONDURAS TO 19N WEST OF 80W TO
BELIZE RESPECTIVELY. A TROPICAL STORM WARNING IS NOW IN EFFECT
FOR THE ENTIRE HONDURAS COAST FROM THE HONDURAS/NICARAGUA BORDER
WESTWARD TO THE GUATEMALA/HONDURAS BORDER AS WELL AS THE ENTIRE
COAST OF BELIZE.

...TROPICAL WAVES...
ON AVERAGE...SIXTY TROPICAL WAVES MOVE OUT OF THE AFRICAN COAST
EVERY YEAR. TODAY...THE 57TH TROPICAL WAVE THAT WE HAS TRACKED
THIS TROPICAL SEASON HAS JUST EMERGED FROM AFRICA...AND IS ADDED
TO THE 1200 UTC SURFACE MAP ALONG 18W/19W BASED ON SATELLITE
PICTURES AND SURFACE DATA. AN ASCAT PASS FROM AROUND 1130 UTC
CONFIRMS THE PRESENCE OF THE WAVE SHOWING ALSO SOME CYCLONIC
TURNING NEAR 11N. IN ADDITION...THE HOVMOLLER DIAGRAM INDICATES
THE WWD PROPAGATION OF THIS SYSTEM WHILE THE TPW PRODUCT FROM
CIMSS REVEALS A NORTH-SOUTH MOISTURE MAXIMUM BETWEEN THE AFRICAN
COAST AND 20W. SCATTERED MODERATE CONVECTION IS FROM 7N-11N
BETWEEN 16W-20W.

A LOW AMPLITUDE TROPICAL WAVE IS ALONG 40W/41W SOUTH OF 14N
MOVING WEST NEAR 10 KT. THE WAVE SHOWS UP VERY WELL ON THE SSMI
TPW PRODUCT FROM CIMSS. AN EARLIER QSCAT PASS SHOWED THE WIND
SHIFT ASSOCIATED WITH THIS FEATURE WITH NE WINDS JUST AHEAD OF
THE WAVE AXIS...AND E TO SE WINDS BEHIND THE WAVE LINE. VIS
SATELLITE IMAGERY SHOWS AN INVERTED-V SIGNATURE. AN AREA OF
MODERATE/ISOLATED STRONG CONVECTION IS AHEAD OF THE WAVE AXIS
AND JUST NORTH OF THE ITCZ FROM 7.5N-11N BETWEEN 41W-44W.
SIMILAR CONVECTION IS WITHIN 140 NM EAST OF THE SOUTH END OF THE
WAVE AXIS.

A WEAK TROPICAL WAVE IS ALONG 58W S OF 18N MOVING W NEAR 10 KT.
THE WAVE IS ALREADY EMBEDDED IN THE CYCLONIC CIRCULATION OF
HURRICANE OMAR WITH MOSTLY SLY WINDS EITHER SIDE OF THE WAVE
AXIS. THIS WAVE IS EXPECTED TO BECOME ABSORBED INTO THE LARGE
CIRCULATION OF OMAR AS IT TRACKS WWD...AND PROBABLY BE DROPPED
FROM THE 18Z SFC MAP.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N14W 7N25W 8N38W 8N50W 9N57W. IN
ADDITION TO CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-10N
BETWEEN 45W-52W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER-LEVEL LOW LOCATED OVER CENTRAL MEXICO NEAR 20N100W IS
PRODUCING A MOIST SLY WIND FLOW OVER THE GULF REGION WEST OF
93W INCLUDING ALSO THE BAY OF CAMPECHE. THESE UPPER-LEVEL WINDS
ARE HELPING TO INDUCE SCATTERED SHOWERS AND ISOLATED TSTMS OVER
THE WRN GULF MAINLY BETWEEN 93W AND 96W. A SURFACE TROUGH...
LIKELY A REFLECTION OF THIS UPPER FEATURE REMAINS OVER THE WEST
GULF AND NOW EXTENDS FROM THE DEEP SOUTH TEXAS TO THE BAY OF
CAMPECHE. SHIP AND BUOY OBSERVATIONS AS WELL AS A QSCAT PASS
FROM AROUND 12Z CONFIRM THE WIND SHIFT ASSOCIATED WITH THIS
SURFACE TROUGH. AN UPPER-LEVEL RIDGE ANCHORED ON A HIGH OVER THE
SE CONUS COVERS THE REMAINDER OF THE GULF AND THE STATE OF
FLORIDA GENERATING STRONG SUBSIDENCE AND THE IMPLIED DRY AND
STABLE ATMOSPHERE. ANOTHER UPPER-LEVEL HIGH IS OVER THE YUCATAN
PENINSULA ASSOCIATED WITH T.D. SIXTEEN IN THE WRN CARIBBEAN. AT
THE SURFACE...HIGH PRESSURE CENTER OVER THE SE CONUS DOMINATES
MUCH OF THE GULF E OF 90W...INCLUDING THE FLORIDA PENINSULA AND
STRAITS OF FLORIDA. THE PRESSURE GRADIENT BETWEEN THIS HIGH AND
T.D. SIXTEEN CONTINUES TO GENERATE MODERATE TO STRONG ELY WINDS
OVER THE CENTRAL AND ERN GULF. AN EARLIER QSCAT PASS SHOWED 20
TO 25 KT ELY WINDS OVER THE EASTERN GULF SOUTH OF 27N AND THE
YUCATAN CHANNEL.

CARIBBEAN SEA...
TWO TROPICAL CYCLONES ARE IN THE CARIBBEAN SEA...ONE IS
HURRICANE OMAR AND THE SECOND ONE IS T.D. SIXTEEN. SEE THE
SPECIAL FEATURES FOR MORE DETAILS. THE UPPER-LEVEL HIGH OVER THE
YUCATAN PENINSULA EXTENDS A RIDGE OVER MUCH OF THE CARIBBEAN SEA
AND CENTRAL AMERICA...AND IS ENHANCING CONVECTION ASSOCIATED
WITH T.D. SIXTEEN. WATER VAPOR IMAGERY REVEALS A DEEP LAYERED
TROUGH ACROSS THE W ATLC DIGGING SWD INTO THE NRN CARIBBEAN.
THIS TROUGH WILL PLAY A ROLE IN TRACKING OMAR TO THE NE OVER THE
NEXT FEW DAYS. UPPER DIFFLUENCE E OF THE UPPER TROUGH ACROSS THE
ERN CARIBBEAN IS PROVIDING AMPLE OUTFLOW FOR THE CONVECTIVE
ACTIVITY ASSOCIATED WITH OMAR. PATCHES OF LOW LEVEL CLOUDS WITH
POSSIBLE SHOWERS ARE REACHING PART OF THE CENTRAL AND EAST CUBA
UNDER A NE WIND FLOW.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE IS ACROSS THE SE CONUS EXTENDING ACROSS THE
W ATLC WATERS AND THE BAHAMAS W OF 71W. MODERATE TO STRONG
SUBSIDENCE IS ASSOCIATED WITH THIS UPPER RIDGE BRINGING DRY AIR
ACROSS THE FLORIDA PENINSULA...NRN CUBA AND THE BAHAMAS. A DEEP
LAYERED TROUGH EXTENDING FROM AN UPPER-LEVEL LOW LOCATED NEAR
31N62W ENTERS THE CARIBBEAN SEA THROUGH HISPANIOLA AND EXTENDS
MAINLY WWD SOUTH OF CUBA. THIS UPPER TROUGH SUPPORTS A SURFACE
TROUGH THAT EXTENDS INTO THE DISCUSSION AREA NEAR 31N55W SW TO
20N65W. A LARGE AREA OF DEEP-LAYERED MOISTURE WITH EMBEDDED
SHOWERS IS AHEAD OF THE TROUGH. THE UPPER-LOW MENTIONED ABOVE IS
GENERATING SOME SHOWER ACTIVITY. A 1012 MB LOW...REMNANTS OF
NANA...CENTERED NEAR 22N48W IS DRIFTING N-NW INTO THE DEEP
LAYERED TROUGH ACROSS THE CENTRAL ATLC. SCATTERED SHOWERS AND
TSTMS ARE WITHIN 70 NM NE QUADRANT. TO THE SE...ANOTHER 1012 MB
LOW IS GENERATING SCATTRED SHOWERS. THE E ATLC IS UNDER THE
INFLUENCE OF A SURFACE RIDGE ANCHORED ON A 1029 MB HIGH CENTERED
NEAR THE AZORES. AN UPPER-LEVEL HIGH CENTERED NEAR 17N48W IS
SUPPORTING CONVECTION ALONG THE ITCZ MAINLY WEST OF 40W. ANOTHER
CELL IS NEAR 9N30W.

$$
GR






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