000
WTNT42 KNHC 072035
TCDAT2
TROPICAL STORM OTTO DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172010
500 PM AST THU OCT 07 2010
 
BURSTS OF DEEP CONVECTION WITH CLOUD TOP TEMPERATURES OF -70C TO
-80C HAVE CONTINUED TO DEVELOP OVER AND EAST OF THE LOW-LEVEL
CENTER DURING THE PAST 6 HOURS. SHEAR PATTERN SATELLITE INTENSITY
ESTIMATES HAVE BEEN VARYING BETWEEN T3.0/45 KT AND T3.5/55 KT.
THEREFORE...THE INITIAL INTENSITY WILL REMAIN AT 50 KT.  ALTHOUGH 
A SMALL UPPER-LEVEL ANTICYCLONE HAS DEVELOPED OVER THE CENTER OF
OTTO...LOWER CIRRUS CLOUD ELEMENTS CAN BE SEEN UNDERCUTTING THE
FAVORABLE OUTFLOW LAYER IN VISIBLE AND WATER VAPOR IMAGERY...WHICH
IS CREATING SOME MODEST UPPER-LEVEL SHEAR CONDITIONS ON THE CYCLONE.
 
THE INITIAL MOTION ESTIMATE IS 050/05. OTTO IS COMING UNDER THE
INCREASING INFLUENCE OF A LARGE DEEP-LAYER TROUGH THAT HAS MOVED
EASTWARD OFF THE U.S. EAST COAST. THE TROUGH IS FORECAST BY ALL OF
THE MODELS TO CONTINUE MOVING EASTWARD AND STEADILY ACCELERATE OTTO
TO THE NORTHEAST DURING THE NEXT 48 HOURS. BY 72 HOURS...OTTO IS
EXPECTED TO MERGE WITH A FRONTAL SYSTEM AND BECOME AN EXTRATROPICAL
CYCLONE AND GALE AREA THAT COULD AFFECT THE AZORES ISLANDS IN 96 TO
120 HOURS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
ADVISORY TRACK AND IS CLOSE TO THE CONSENSUS MODEL...TVCN.

SLOW STRENGTHENING IS EXPECTED DURING THE NEXT 24 HOURS OR SO WHILE
OTTO REMAINS OVER WARM SSTS AND ALSO MOVES INTO AN AREA OF
INCREASING INSTABILITY LOCATED IN THE EASTERN SEMICIRCLE. VERTICAL
WIND SHEAR IS EXPECTED TO DECREASE SLIGHTLY BETWEEN 24 AND 36
HOURS...AND THAT IS WHEN OTTO COULD POSSIBLY REACH HURRICANE
STRENGTH AS SUGGESTED BY THE GFDL/HWRF MODELS. HOWEVER...THIS WOULD
LIKELY BE SHORT-LIVED DUE TO INCREASING WESTERLY SHEAR. BY 72
HOURS...OTTO IS EXPECTED TO ENCOUNTER STRONGER SHEAR OF 35-40
KT...WHICH SHOULD HASTEN THE WEAKENING PROCESS. HOWEVER...OTTO IS
EXPECTED TO BE AN EXTRATROPICAL GALE AREA BY THAT TIME...AND THE
INFUSION OF BAROCLINIC ENERGY SHOULD HELP MAINTAIN THE CYCLONE. THE
OFFICIAL OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY AND IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE.


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 24.0N  67.6W    50 KT
 12HR VT     08/0600Z 24.7N  66.3W    55 KT
 24HR VT     08/1800Z 26.1N  63.8W    60 KT
 36HR VT     09/0600Z 28.4N  59.7W    60 KT
 48HR VT     09/1800Z 30.8N  54.5W    55 KT
 72HR VT     10/1800Z 35.7N  42.3W    50 KT...POST-TROP/EXTRATROP
 96HR VT     11/1800Z 39.0N  29.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     12/1800Z 37.0N  23.5W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART