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Tropical Storm Julian Discussion Number   3
NWS National Hurricane Center Miami FL       AL112021
1100 AM AST Sun Aug 29 2021
 
The system has become better organized this morning, with the 
low-level center located on the southwestern edge of a persistent 
mass of deep convection.  A 1246 UTC ASCAT-B pass revealed an area 
of winds over 40 kt southeast of the center, so the system is 
upgraded to Tropical Storm Julian with maximum winds of 45 kt.
 
Julian is accelerating toward the northeast (045/15 kt) in the flow 
to the south of a deep-layer area of low pressure located just east 
of Newfoundland.  The storm is expected to move around the 
southeastern and eastern periphery of this large low during the next 
few days, accelerating further and turning toward the north by 48 
hours.  The track models are all in good agreement on this scenario, 
and the NHC track forecast is very close to the TVCA and HCCA 
consensus aids.  This new forecast is also relatively unchanged from 
the previous advisory.
 
Winds in the storm have increased faster than expected, even in the 
face of 20 kt of west-southwesterly shear.  This shear is forecast 
to increase substantially in the coming days, with SHIPS diagnostics 
indicating it may reach magnitudes of 40-50 kt. However, the storm 
will still be moving over marginally warm waters around 26 degrees 
Celsius, and its fast motion and some baroclinic forcing could allow 
for additional strengthening during the next 12-24 hours.  Nearly 
all the intensity models support some strengthening, and the NHC 
official forecast peaks the winds at 55 kt in 24 hours, roughly 
between the IVCN and HCCA solutions. Phase-space diagrams suggest 
that Julian will probably already be going through extratropical 
transition at that time, and it should be fully extratropical by 36 
hours.  Gradual weakening is anticipated after 24 hours, and the 
extratropical low is likely to dissipate over the north Atlantic by 
day 3.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 35.1N  46.8W   45 KT  50 MPH
 12H  30/0000Z 36.9N  43.7W   50 KT  60 MPH
 24H  30/1200Z 40.0N  39.7W   55 KT  65 MPH
 36H  31/0000Z 43.6N  37.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  31/1200Z 48.0N  36.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  01/0000Z 52.2N  38.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  01/1200Z...DISSIPATED
 
$$
Forecaster Berg
 
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