ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM LISA DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT MON SEP 20 2004 LISA REMAINS A SMALLER THAN AVERAGE TROPICAL CYCLONE. BANDING FEATURES HAVE CONTINUED TO IMPROVE THIS MORNING...INCLUDING AND OCCASIONAL HINT OF A BANDING EYE FEATURE IN VISIBLE IMAGERY. MICROWAVE IMAGERY FROM 20/0903Z AMSU AND 20/0955Z SSMI OVERPASSES REVEALED A SMALL MID-LEVEL EYE WAS PRESENT. SUCH FEATURES ARE TYPICALLY ASSOCIATED WITH 45-55 KT TROPICAL CYCLONES. THE INITIAL INTENSITY ESTIMATE WAS INCREASED TO 50 KT BASED ON RECENT UW-CIMSS AND CIRA AMSU PRESSURE ESTIMATES OF 999.1 AND 998 MB... RESPECTIVELY. THEREFORE...THE INITIAL INTENSITY HAS BEEN MADE HIGHER THAN THE DVORAK SATELLITE INTENSITY ESTIMATES OF 35 KT FROM BOTH TAFB AND SAB...AND 30 KT FROM AFWA. THE INITIAL MOTION ESTIMATE REMAINS 275/10. THERE REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK FORECAST OR REASONING. LISA IS EXPECTED TO MOVE IN A WEST TO WEST-NORTHWESTWARD MOTION THROUGHOUT THE FORECAST PERIOD AS THE SMALL CYCLONE MOVES AROUND THE PERIPHERY OF A NARROW SUBTROPICAL TO THE NORTH. THE RIDGE CURRENTLY BETWEEN LISA AND KARL TO THE NORTHWEST IS FORECAST BY MOST OF THE MODELS TO REMAIN INTACT TO SOME DEGREE. THE NOGAPS MODEL IS THE ONLY MODEL THAT WEAKENS THE RIDGE AND PULLS LISA NORTHWARD AFTER 72 HOURS. HOWEVER...NOGAPS IS THE ONLY MODEL THAT EVEN IDENTIFIES LISA BEYOND 24-36 HOURS...AND IT APPEARS TO BE SUFFERING FROM ITS USUAL OVERDEVELOPMENT OF THE CYCLONE...WHICH ALLOWS LISA TO ERODE THE NARROW RIDGE AND MOVE THROUGH IT. THIS SOLUTION HAS BEEN DISCOUNTED GIVEN THE CURRENT VERY SMALL DIAMETER OF LISA...AND THE STRONG HIGH PRESSURE SYSTEM TO THE NORTH EXPECTED TO KEEP THE DIAMETER OF THE CYCLONE SMALLER THAN AVERAGE THROUGHOUT THE FORECAST PERIOD. THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK AND IS CLOSE TO THE GFDL AND DEEP BAM MODELS. SMALL COMPACT TROPICAL CYCLONES LIKE LISA ARE SUSCEPTIBLE TO SHARP CHANGES IN INTENSITY...BOTH STRENGTHENING AND WEAKENING. THE VERTICAL SHEAR IS FORECAST TO REMAIN AROUND 10 KT OR LESS FOR THE NEXT 24 HOURS...SO STRENGTHENING INTO A HURRICANE SEEMS LIKELY...PERHAPS EVEN BY LATER TODAY. BY 36 HOURS...LOW TO MODERATE NORTHEASTERLY VERTICAL SHEAR IS EXPECTED TO INHIBIT INTENSIFICATION ...SO ONLY SLOW STRENGTHENING IS FORECAST IN THE LONGER TIME PERIODS. IF LISA REMAINS SOUTH OF 15N LATITUDE WHERE THE SHEAR IS EXPECTED TO BE THE STRONGEST...THEN THE INTENSITY WILL LILELY BE LESS THAN WHAT IS CURRENTLY FORECAST AND INDICATED BY THE SHIPS INTENSITY MODEL. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 13.6N 35.9W 50 KT 12HR VT 21/0000Z 13.8N 37.3W 55 KT 24HR VT 21/1200Z 14.3N 39.1W 65 KT 36HR VT 22/0000Z 14.8N 40.6W 70 KT 48HR VT 22/1200Z 15.5N 42.4W 75 KT 72HR VT 23/1200Z 16.8N 45.5W 75 KT 96HR VT 24/1200Z 17.0N 48.5W 75 KT 120HR VT 25/1200Z 17.0N 51.5W 75 KT $$ NNNN
Alternate Formats
About Alternates -
E-Mail Advisories -
RSS Feeds
Cyclone Forecasts
Latest Advisory -
Past Advisories -
About Advisories
Marine Forecasts
Latest Products -
About Marine Products
Tools & Data
Satellite Imagery -
US Weather Radar -
Aircraft Recon -
Local Data Archive -
Forecast Verification -
Deadliest/Costliest/Most Intense
Learn About Hurricanes
Storm Names
Wind Scale -
Prepare -
Climatology -
NHC Glossary -
NHC Acronyms -
Frequently Asked Questions -
AOML Hurricane-Research Division
About Us
About NHC -
Mission/Vision -
Other NCEP Centers -
NHC Staff -
Visitor Information -
NHC Library
NOAA/
National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida, 33165-2149 USA
nhcwebmaster@noaa.gov
Disclaimer
Privacy Policy
Credits
About Us
Glossary
Career Opportunities
Page last modified: Monday, 20-Sep-2004 15:03:28 UTC