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Tropical Storm Frank Discussion Number 2
NWS National Hurricane Center Miami FL EP072022
1000 AM CDT Tue Jul 26 2022
Satellite imagery this morning depicts a sheared bursting pattern
associated with the tropical cyclone. An overnight convective burst
obscured the low-level circulation center, but first-light visible
imagery now shows the vortex mostly exposed east of the colder
convective cloud tops. This structure can also be seen from the last
couple SSMIS microwave passes near the center and is characteristic
of environmental vertical wind shear (VWS) diagnosed between 15-20
knots from the northeast. Subjective Dvorak intensity estimates from
TAFB and SAB were T2.5/35-kt and T2.0/30-kt respectively, while the
latest UW-CIMSS ADT estimate was at T2.5/35-kt. The initial
intensity has been raised to 35-kt this advisory, upgrading the
tropical depression to tropical storm Frank.
Northeasterly VWS between 15-20 kt is expected to continue over the
next 48 hours, and will likely limit significant intensification in
the short-term as the shear promotes misalignment between the
low-level and mid-level centers. The latest intensity forecast only
shows slow intensification in the short-term. Afterwards, this shear
is expected to decrease, while the storm will remain over warm
sea-surface temperatures near 29C through 96 hours. However, the
current shear may also help broaden Frank's wind field as convection
is favored outside of the radius of maximum wind, as suggested by
the latest ECMWF run. These structural changes could limit more
robust intensification later in the forecast despite the more
favorable environment. For now, the latest NHC forecast still peaks
Frank as a category 1 hurricane towards end of the forecast period.
This forecast is on the lower end of the intensity guidance
envelope, close to the LGEM model, and is somewhat lower than the
consensus aids HCCA and IVCN.
The tropical storm is moving generally westward at 280/9-kt. The
track guidance is in fairly good agreement that this motion and
heading will continue as a mid-level ridge extends westward to the
north of Frank over the next 2-3 days. Towards the end of the
forecast, the ridge overhead will begin to gradually weaken, and
will likely allow a larger Frank to begin gaining more latitude. One
complicating factor in the track forecast is the possibility of some
weak binary interaction with another low-level circulation located
to Frank's northwest, where the net interaction may help impart a
bit more northerly heading to Frank's track between 72-96 hours. For
now, the track forecast continues to favor a blend of the GFS and
ECMWF forecast (GFEX) and is quite close to the previous forecast
track.
FORECAST POSITIONS AND MAX WINDS
INIT 26/1500Z 11.6N 102.4W 35 KT 40 MPH
12H 27/0000Z 11.9N 104.1W 40 KT 45 MPH
24H 27/1200Z 12.1N 105.9W 40 KT 45 MPH
36H 28/0000Z 12.2N 107.6W 45 KT 50 MPH
48H 28/1200Z 12.6N 109.5W 45 KT 50 MPH
60H 29/0000Z 12.9N 111.3W 50 KT 60 MPH
72H 29/1200Z 13.6N 113.1W 65 KT 75 MPH
96H 30/1200Z 15.0N 116.5W 80 KT 90 MPH
120H 31/1200Z 17.5N 119.5W 80 KT 90 MPH
$$
Forecaster Papin
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