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Tropical Storm Carlos Discussion Number   5
NWS National Hurricane Center Miami FL       EP032021
200 PM PDT Sun Jun 13 2021
 
Deep convection has managed to persist over the center of Carlos 
throughout the day today, although the appearance of this convection 
has become more ragged as the day has progressed. The blended CI 
values from TAFB and SAB suggest the system still has an intensity 
of 45 kt. A recent ASCAT overpass only partially captured the 
circulation with peak wind vectors of 39 kt. Compensating for 
possible undersampling by the instrument over only a portion of 
such a compact cyclone, maintaining 45 kt seems reasonable for the 
initial advisory intensity.

Dry and stable air lies just to the north and west of Carlos, and 
occasional intrusions of this air into the cyclone's circulation 
could disrupt convection. However, the overnight diurnal convective 
maximum could overcome these intrusions over the next couple of 
nights. Therefore, only slight weakening is indicated through that 
time period. By 48 h, Carlos is expected to move into the stable 
airmass which should further disrupt its convection, causing 
additional weakening. By late in the forecast period the cyclone 
is forecast to be near or have crossed the 26 degree C SST 
isotherm. This should cause any remaining convection to gradually 
dissipate. Although not shown in the official forecast, it is 
possible Carlos will degenerate into a remnant low by the end of 
the forecast period, as suggested by the GFS. The latest NHC 
intensity forecast is very near the various multi-model consensus 
solutions.
 
Carlos is beginning to show signs of slowing and turning to the 
left, with the initial motion now 260/6 kt. Model guidance remains 
in good agreement through 48 h, with the storm slowing and turning 
west-southwest as a mid-level ridge becomes oriented SW-NE to the 
north of the cyclone. There is still a vast amount of track guidance 
spread beyond 72 h, but not as much as earlier today. The GFS, which 
continues to be the easternmost solution has shifted well west of 
its previous track, showing Carlos turning northwest in a few days 
in response to a building ridge to its east, and weakening ridge to 
the north. The remaining guidance maintains the ridge to the north 
and shows Carlos turning west by midweek, then west-northwest by 
late this week. The official NHC forecast is near the previous one 
through 48 h. Beyond 48 h, large adjustments were required to 
accommodate the continuing westward trends in the guidance. 
Despite the abrupt shift in the official forecast for the latter 
half of the period, it remains well east of the consensus and the 
majority of available track guidance.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/2100Z 11.7N 126.6W   45 KT  50 MPH
 12H  14/0600Z 11.4N 127.4W   40 KT  45 MPH
 24H  14/1800Z 11.0N 128.3W   40 KT  45 MPH
 36H  15/0600Z 10.6N 129.2W   40 KT  45 MPH
 48H  15/1800Z 10.4N 130.0W   35 KT  40 MPH
 60H  16/0600Z 10.3N 130.8W   30 KT  35 MPH
 72H  16/1800Z 10.3N 131.3W   30 KT  35 MPH
 96H  17/1800Z 10.7N 132.0W   25 KT  30 MPH
120H  18/1800Z 11.4N 132.7W   25 KT  30 MPH
 
$$
Forecaster Latto
 
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