[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 300228
TCDAT3
TROPICAL STORM LISA DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT WED SEP 29 2004

A RAGGED EYE-LIKE FEATURE HAS APPEARED IN INFRARED IMAGERY. HOWEVER
...CONVECTION SURROUNDING THIS FEATURE IS SHALLOW WITH THE STRONGEST
CONVECTION CONFINED TO THE SOUTHERN QUADRANT. A 29/1657Z CIMSS AMSU
PRESSURE ESTIMATE WAS 981.7 MB AND A 29/2048Z QUIKSCAT OVERPASS
REVEALED ONE 60-KT NON-RAINFLAGGED WIND VECTOR...SURROUNDED BY
SEVERAL 50-55 KT UNFLAGGED VECTORS...IN THE DRY SLOT REGION IN THE
SOUTHEAST QUADRANT. BASED ON THIS INFORMATION AND THE RAGGED EYE
FEATURE...THE INITIAL INTENSITY IS BEING MAINTAINED AT 60 KT...
DESPITE THE MUCH LOWER DVORAK SATELLITE INTENSITY ESTIMATES.

THE INITIAL MOTION IS 340/09. LISA REMAINS ON TRACK AND IS NOW
MOVING NORTH-NORTHWESTWARD AROUND THE NORTHEAST PERIPHERY OF AN
UPPER-LEVEL LOW. AS THE LOW DROPS TO THE SOUTH...LISA IS EXPECTED
TO BRIEFLY TURN NORTHWESTWARD BEFORE TURNING SLOWLY NORTHWARD
THROUGH A BREAK IN THE SUBTROPICAL RIDGE AXIS. BY 48 HOURS...THE
CYCLONE IS FORECAST TO GET PICKED UP BY AN APPROACHING SHORTWAVE
TROUGH...AND BECOME EXTRATROPICAL OR MERGE WITH AN EXTRATROPICAL
LOW BY 72 HOURS. THE OFFICIAL FORECAST IS A LITTLE TO THE RIGHT OF
THE MODEL CONSENSUS DUE TO THE THE GFDL APPEARING TO BE AN EXTREME
WESTERN OUTLIER MODEL THAT IS PRODUCING A CONSENSUS WEST BIAS.

THE WINDOW OF OPPORTUNITY FOR ADDITIONAL STRENGTHENING IS GRADUALLY
CLOSING. LISA HAS A SHALLOW EYE FEATURE AND WILL BE OVER 26C SSTS
FOR ANOTHER 12 HOURS OR SO...WHILE REMAINING UNDER VERY LOW
VERTICAL SHEAR CONDITIONS. THEREFORE...IT IS POSSIBLE THAT LISA
COULD DEVELOP ENOUGH CONVECTION AROUND THE RAGGED EYE FEATURE LATER
TONIGHT DURING THE USUAL NOCTURNAL CONVECTIVE MAXIMUM PERIOD...
ALLOWING THE CYCLONE TO BRIEFLY BECOME A HURRICANE. BY 24 HOURS...
LISA WILL BE MOVING OVER 25C AND LOWER SSTS...WHICH SHOULD BRING
ABOUT SLOW WEAKENING EVEN THOUGH THE SHEAR IS FORECAST TO BE LESS
THAN 10 KT.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      30/0300Z 31.5N  46.2W    60 KT
 12HR VT     30/1200Z 32.8N  47.0W    65 KT
 24HR VT     01/0000Z 34.7N  47.5W    60 KT
 36HR VT     01/1200Z 36.7N  47.0W    60 KT
 48HR VT     02/0000Z 38.6N  45.0W    55 KT...BECOMING EXTRATROPICAL
 72HR VT     03/0000Z 42.5N  37.5W    45 KT...EXTRATROPICAL
 96HR VT     04/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW


$$This weather bulletin was brought to you by:
www.nashvilleweather.net