Eastern Pacific Basin Tropical Cyclones

Tropical Storm Frank Forecast Discussion


022 
WTPZ42 KNHC 261451
TCDEP2

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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