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Tropical Depression Seven-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP072020
1100 PM HST Sun Jul 19 2020

The small low pressure are that the National Hurricane Center has 
been tracking for the past couple of days has finally developed 
enough persistent organized deep convection for the  system to 
classified as Tropical Depression Seven-E. An earlier burst of 
strong convection with cloud tops colder than -80C helped to spin up 
the low-level wind field and cause the center to become better 
defined based on a 0529 UTC ASCAT-A overpass. The aforementioned 
scatterometer data showed surface winds of 29-30 kt in the western 
semicircle, which is the basis for the 30-kt initial intensity. This 
intensity is also supported by 06Z Dvorak satellite intensity 
estimates of T2.0/30 kt from both TAFB and SAB.

The initial motion estimate is 310/10 kt based on conventional, 
microwave, and scatterometer satellite fix data over the past 12 
hours. The small cyclone is expected to be steered northwestward to
west-northwestward at about the same forward speed for the next day 
or so due to a strong subtropical ridge situated to the north of the 
depression. By 24-36 h, the system is forecast to degenerate into a 
shallow remnant low and be steered westward through 48-60 h, 
followed by a turn toward the southwest before dissipating by 96 h. 
The NHC official forecast track lies close to the tightly packed 
simple consensus models, which is consistent with the NOAA 
corrected-consensus model, HCCA.

Although the vertical wind shear is expected to remain low at less 
than 5 kt for the next 24 h or so, the small cyclone is already 
moving over sub-26 deg C sea-surface temperatures (SST), with 
slightly cooler water ahead of the system. The ingestion of cooler 
and drier air, along with the cool SSTs, is expected to weaken the 
system below depression status by 24 h. Although it is possible that 
the system could hold on to tropical cyclone status a little longer 
than currently indicated, especially when the system moves 
southwestward toward warmer water, moderate to strong southwesterly 
vertical wind shear should cause the small cyclone to dissipate by 
96 h. The official intensity forecast closely follows the IVCN 
intensity consensus model.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/0900Z 18.0N 129.3W   30 KT  35 MPH
 12H  20/1800Z 18.7N 130.7W   30 KT  35 MPH
 24H  21/0600Z 19.3N 132.6W   25 KT  30 MPH...POST-TROPICAL
 36H  21/1800Z 18.9N 134.8W   25 KT  30 MPH...POST-TROPICAL
 48H  22/0600Z 18.0N 137.2W   20 KT  25 MPH...POST-TROPICAL
 60H  22/1800Z 16.0N 139.6W   20 KT  25 MPH...POST-TROPICAL
 72H  23/0600Z 13.7N 141.9W   20 KT  25 MPH...POST-TROPICAL
 96H  24/0600Z...DISSIPATED
 
$$
Forecaster Stewart
 
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