Tropical storm Flossie to hit Hawaii today; will Dorian come back to life in Atlantic?

July 29, 2013

Tropical Storm Flossie formed last Thursday in the eastern Pacific, and has been innocently trekking westward since then. Today, it will make landfall on Hawaii with a burst of wind and rain, and high surf. All of the Hawaiian islands are under a tropical storm warning.

Enhanced infrared satellite image of Flossie from 8:30am EDT today. (NOAA)
Enhanced infrared satellite image of Flossie from 8:30am EDT today. (NOAA)

According to the Central Pacific Hurricane Center, Flossie has maximum sustained winds of 45 mph and is heading west at 16 mph. It’s just 120 miles east of Hilo on the Big Island, where landfall is expected this morning. Interestingly, Flossie’s last reincarnation in 2007 also passed close to the Big Island, but as a Category 2 hurricane.

A tropical cyclone landfall on (or passing near) Hawaii is not common but not exactly rare. Reliable records only go back about 60-65 years. But, in that period, 23 storms have passed within 200 miles of the islands (or one about every three years), 4 in July. Of those 23, Iniki 1992 was by far the strongest and most destructive, followed by Estelle in 1986.


Tracks of the previous 23 known tropical cyclones since 1950 that passed near the Hawaiian islands. (NOAA)

Most storms affecting Hawaii weaken significantly before reaching the islands; Flossi is no exception.

The southern islands will experience worse weather than the northern islands, with some areas likely to get tropical storm force winds and periods of heavy rain.  The storm is poorly organized with minimal thunderstorm activity, so this encounter could certainly have been much worse.

There is a long-range radar loop from the Big Island that will aid in tracking the center and the rainfall.  The ensemble tropical rainfall potential, or eTRaP, is a consensus of seven models, and offers an objective rainfall forecast over the next 24 hours: it is showing isolated peak amounts of about 4 inches over the the Big Island of Hawaii, although higher amounts are certainly possible at high elevations.

After Flossi’s encounter with the islands, it is expected to dissipate completely by the end of the week.

Model-based 24-hour rainfall forecast across the Hawaiian islands. (NOAA)
Model-based 24-hour rainfall forecast across the Hawaiian islands. (NOAA)

Dorian

Moving back to the Atlantic basin, Dorian degenerated into an open wave on Saturday evening, and the National Hurricane Center ceased issuing advisories on it. However, it is (and has been) very close to becoming a tropical depression or storm again. There is renewed deep convection firing over the mid-level circulation today, but still no evidence of a closed surface circulation. Another aircraft reconnaissance may be tasked later today to confirm this.


Remnants of Dorian north of Puerto Rico on Monday morning. (NOAA)

Although the ocean temperature under the storm has increased notably over the past few days, wind shear and dry air continue to plague it. Depending on if and how it interacts with land in a few days, it could redevelop in the Gulf of Mexico, but that’s a topic of discussion for later in the week.


Forecast tracks from 8 dynamical models. None of them forecast noteworthy strengthening. (U. Albany)

In the near future, the worst it will do is bring gusty winds and increased chances of heavy rain to Puerto Rico, Dominican Republic, Haiti, and eastern Bahamas. However, it is still worth keeping a very close eye on, since any unexpected relaxation of the shear could allow it to organize much more quicker than currently forecast. The phrase “Bahama Buster” generally refers to weak storms that rapidly intensify over the very warm waters of the Bahamas.

* Brian McNoldy is a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

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Jason Samenow · July 29, 2013