Since the tropics have been reasonably quiet all August, this quick burst of activity has a lot of people’s attention. This increase in activity isn’t unusual. Now that we are getting closer to September and the peak of Hurricane Season, the tropics tend to get a bit more active.
Latest on Dorian
The latest advisory from the National Hurricane Center:
SUMMARY OF 800 PM AST…0000 UTC…INFORMATION
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LOCATION…11.6N 54.8W
ABOUT 335 MI…540 KM ESE OF BARBADOS
ABOUT 445 MI…715 KM ESE OF ST. LUCIA
MAXIMUM SUSTAINED WINDS…50 MPH…85 KM/H
PRESENT MOVEMENT…W OR 280 DEGREES AT 14 MPH…22 KM/H
MINIMUM CENTRAL PRESSURE…1003 MB…29.62 INCHES
Tropical Storm Dorian has winds of 50mph. It is a pretty small storm. Data shows that the maximum wind radius is around 10 miles. It is moving west at 14mph and is expected to slow down a bit and then shift west-northwest in the coming days.
From the National Hurricane Center
While still looking a bit ragged, convection has continued to increase near the center of Dorian since the last advisory, and a just-received SSMI/S overpass shows a convective band wrapped about three-quarters of the way around the center. Various Dvorak-based objective and subjective satellite intensity estimates are in the 35-45 kt range, while recent microwave-based estimates are in the 45-60 kt range. Based on these data, the initial intensity is increased to 45 kt.
The initial motion remains 280/12 kt. The subtropical ridge to the north of the cyclone should steer it generally westward to west-northwestward for the next 72 h or so, with a more northwestward motion possible thereafter as Dorian approaches an upper-level low pressure area forecast to be over the north-central Caribbean. The model guidance has not shifted much since the previous advisory. However, some of the normally reliable models are in disagreement. The ECMWF and GFS keep Dorian weaker and farther south, and they are on the left side of the guidance envelope. The HWRF and UKMET have more northerly tracks, and forecast Dorian to pass near Puerto Rico and then near or north of Hispaniola. The various consensus models are between these extremes, and the earlier forecast is now close to them. Thus, the new forecast track is little changed from the previous forecast, and it calls for Dorian to move through the Windward Islands between 36-48 h and cross Hispaniola between 96-120 h.
Dorian still appears to be ingesting dry air based on the somewhat ragged convective pattern. This entrainment is expected to continue sporadically for the next 2-3 days, and this could slow intensification despite an environment of light to moderate shear. The intensity guidance is split on how much intensification could occur during this time. The statistical-dynamical SHIPS and LGEM models showing more intensification and forecast Dorian to become a hurricane. On the dynamical side, the latest HWRF run shows little development, and the GFS/ECMWF keep the system weak to the point where it degenerates into a tropical wave before reaching Hispaniola. The intensity forecast follows the general trend of the statistical-dynamical models, but shows less intensification out of respect for the dynamical models. The intensity forecast becomes even lower confidence after 72 h due to uncertainties in how much shear and land that Dorian will encounter. The new forecast calls for Dorian to weaken to a depression due to passage over Hispaniola. However, the large range of possibilities also includes both Dorian going north of Hispaniola and remaining a hurricane and the small cyclone dissipating completely over the island.
Detailed scientific breakdown from Levi Cowan
Levi is a veritable treasure chest of tropical meteorology knowledge. He produces these breakdown videos that can get pretty detailed (probably more detailed than even I get on this blog at times) and sciencey.
Take a look:
Levi also runs the website, Tropical Tidbits, which is a fantastic resource.
