Whats in a name: Gonzalo, Douglas, and TD8 (23 July 2020)

After a long boring spell, the tropics got “interesting” all of the sudden.  Two storms in the Atlantic, and one headed to Hawai’i, so will be lot to cover today! But first we’ll start with a brief overview of how storms are tracked and named.

Last night the US National Hurricane Center started public advisories on the suspicious (investigation) area in the Gulf of Mexico.  As a reminder, tropical systems (Hurricanes, Typhoons, Cyclones, etc) are given unique formal identifiers when the reach a certain level of organization and intensity.   The first two letters are the Basin (area of world’s ocean – AL for Atlantic, EP for east pacific, CP for central pacific/Hawaii, WP west pacific, IO Indian Ocean, SH southern hemisphere).  The next two digits are the storm number for that year, followed by the year.  Storms are also given informal names to help in public awareness and watch/warnings. The number codes (called ATCF identifiers) are important since names are reused unless a storm causes a lot of damage and the name retired.  In the Pacific it is also important since some weather agencies (The Philippines for example) use their own names that are different from the other regionally accepted names.  Investigation areas are given temporary storm ids  in the 90 to 99 range, which are reused during the year since most of these don’t spin up.  So the system in the Gulf that had been given the temporary ID of AL912020 now has the formal tracking ID of AL082020.  In advisories it is being called “Tropical Depression Number Eight or TD8.  If it reaches tropical storm force intensity, it will be given the informal name Hanna.  But you will always be able to find it as AL082020.

So what is TD8 up to?  I again want to push the NHC’s “Key Messages” summaries.  They are a great, minimal hype, one-stop official summary of what you need to know about a storm, at least in the National Weather Service area of responsibility (Atlantic and East/Central Pacific regions). They are also available in Spanish, for those serving  Spanish speaking communities.  TD8 still isn’t that organized, but conditions aren’t unfavorable, so NHC is still thinking it will become a minimal tropical storm  before landfall.  Economic impact/damage should be minimal as well, under $10 Million if this forecast holds.  The key question is if significant evacuations become necessary.  Only those at risk from flooding, or in weaker structures like mobile homes should be seeking shelter – we really don’t need lots of people congregating in Texas right now with the COVID19 causing virus in uncontrolled community spread … here’s the impact swath:

The second storm out in the Atlantic is Tropical Storm Gonzalo (AL072020).  Gonzalo has expanded and intensified, and is expected to pass south of Barbados and across the Windward Islands in about two and a half days.  It is forecast to become a hurricane by late this afternoon, and maintain that strength as is crosses the Islands.  After that is a bit uncertain – there is a mass of unfavorable dry air in the central Caribbean that should knock Gonzalo down pretty quickly before it reaches Jamaica.  Impacts are estimated at under $5 Million on this track.

Finally we have Major Hurricane Douglas.  Douglas is an impressive Category 3 hurricane, but fortunately no where near land at the moment.  It is forecast to hold this strength today, but should begin to decay as it approaches the islands of Hawai’i in about 3-4 days and should be just below hurricane strength as it passes over the islands.  Here is the TAOS/TC “plain English” impact map:

The main risks from Douglas at this point seem to be heavy rainfall, but winds could still be over hurricane force along higher elevations and ridgelines.  We’ll know more in a day or so once it starts to decay.

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