23 July 2020

Hurricane watch for Windwards, tropical storm watch for Texas

Shortly after my post yesterday, Tropical Depression 7 was indeed upgraded to Tropical Storm Gonzalo, making it the earliest seventh named storm on record by two days. Centered about 850 miles east of the Windward Islands (the southern portion of the Lesser Antilles), it has peak sustained winds of 65 mph. It is right on the southern periphery of a Saharan Air Layer, and appears to be ingesting some of the dry and dusty air into its circulation.  It's quite anemic on satellite images today, especially compared to yesterday.

Its future is anything but certain.  Many model solutions indicate that it will dissipate completely in the Caribbean, while a few indicate a respectable Category 1-2 hurricane in the near future. There are a few reasons for the extreme differences. 1) Gonzalo is really small, so courser-resolution models struggle with that, 2) it is tracking on a knife's edge of really dry air, and 3) the exact track forecast could bring it into really strong vertical wind shear, or only moderate shear.

But, in the meantime, tropical storm force winds are expected to arrive in the Windward Islands on Saturday. A hurricane watch is in effect because of the possibility (and official forecast) that Gonzalo could be a hurricane at that point.

The disturbance in the central Gulf of Mexico was upgraded to Tropical Depression 8, and could soon be upgraded again to Tropical Storm Hanna.  The average date of 8th named storm formation is September 17th, and the record earliest is August 3rd (Harvey in 2005).  Recall that 2020 already set the record for earliest 3rd, 5th, 6th, and 7th named storm formation... why not keep going? 

It's centered south of central Louisiana and moving toward the west-northwest at 9 mph. It is expected to reach the Texas coast on Saturday morning, but heavy rain and tropical storm force winds will arrive throughout the day on Friday.  The greatest risk of flash flooding exists along the LA and TX coastline through the end of the weekend.

Much further east, a new tropical wave is just exiting the African coast today and there is some model guidance that supports it developing in a few days, but the large-scale environment is likely too hostile for the next 2-3 days.

When the time comes, the next couple of names on this year's list are Isaias (introduced in the 2014 list after Ike was retired in 2008, but 2014 only got to Hanna, so Isaias has not been used yet) and Josephine.

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