Skip Navigation Links
NOAA NOAA United States Department of Commerce

Potential Tropical Cyclone SIX

Potential Tropical Cyclone Six Discussion Number   4
NWS National Hurricane Center Miami FL       AL062021
1100 AM AST Tue Aug 10 2021

Satellite imagery shows that the disturbance has become better 
organized since yesterday, and satellite intensity estimates from 
TAFB and SAB are at tropical storm strength.  However, reports from 
a NOAA Hurricane Hunter aircraft and surface observations indicate 
that the system does not yet have a well-defined closed 
circulation, with the wind and pressure fields more resembling an 
open wave,  The maximum flight-level winds at 925 mb were 35-40 kt, 
and reliable SFMR wind estimates were near 30 kt.  Based on these 
data, the system remains at potential tropical cyclone status with 
an initial intensity of 30 kt.

The initial motion remains west-northwestward or 295/16 kt.  A 
strong low- to mid-level ridge to the north should steer the system 
generally west-northwestward for the next 72 h with some decrease in 
forward speed after 24 h.  Beyond that time, a turn toward the 
northwest with an further decrease in forward speed is likely while 
the system moves near the western periphery of the ridge.  The track 
guidance has changed little since the previous advisory.  So, the 
new NHC track also has little change, and it lies near the various 
consensus models.  Users are reminded that the average track errors 
at days 4 and 5 are 175 miles and 200 miles, respectively.

Conditions continue to appear favorable for strengthening before the 
system reaches Hispaniola in about 24 h, although there may be dry 
air entraining into the system in the southeastern quadrant.  The 
intensity forecast will follow the previous prediction in calling 
for the disturbance to become a tropical storm before landfall, 
followed by weakening to a depression.  The remainder of the 
intensity forecast has lower confidence due to possible land 
interaction with Cuba and differences in the upper-level wind 
forecasts among the various global models.  The new intensity 
forecast will call for slow intensification from 60 h onward, 
similar to the previous one. 

1. The system is forecast to become a tropical storm as it moves
over the northeastern Caribbean Sea today or tonight  Tropical 
storm conditions are expected in portions of the U.S. Virgin 
Islands and Puerto Rico beginning this afternoon, and in the 
Dominican Republic by Wednesday.  Tropical storm conditions are 
possible in northern Haiti and the southeastern Bahamas by late 
2. Heavy rainfall could lead to flash, urban, and small stream 
flooding, along with possible rapid river rises and the potential 
for mudslides across the U.S. Virgin Islands and Puerto Rico. The 
greatest threat for flooding impacts will be across the eastern and 
southern portions of Puerto Rico.
3. There is a risk of wind and rainfall impacts elsewhere in
portions of Hispaniola, the Bahamas, and Cuba later this week,
although the forecast is more uncertain than usual since the system
is still in its formative stage. Interests in these areas should
monitor the system's progress and updates to the forecast.
4. Interests in Florida should monitor updates to the forecast for 
this system, but it is too soon to determine what if any impacts 
could occur there by late this week or this weekend given the 
uncertainty in the long-range forecast.
INIT  10/1500Z 16.3N  63.8W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  11/0000Z 17.3N  66.1W   35 KT  40 MPH...TROPICAL CYCLONE
 24H  11/1200Z 18.5N  68.9W   40 KT  45 MPH...INLAND
 36H  12/0000Z 19.6N  71.4W   30 KT  35 MPH...INLAND
 48H  12/1200Z 20.7N  73.9W   30 KT  35 MPH...OVER WATER
 60H  13/0000Z 21.7N  76.0W   35 KT  40 MPH
 72H  13/1200Z 22.7N  78.1W   35 KT  40 MPH
 96H  14/1200Z 25.0N  82.0W   40 KT  45 MPH
120H  15/1200Z 27.5N  84.0W   50 KT  60 MPH
Forecaster Beven