20 September 2019

Jerry's turn to take aim at Bermuda, next storm brewing over Africa

As of 8am EDT on Friday, Jerry has strengthened to a Category 2 hurricane with 100 mph peak sustained winds and will pass north of the Leeward Islands later today.  Since the wind field is quite small, impacts on the islands will be minimal, but tropical storm watches are up.  The hurricane also looks very ragged today, hardly the mental image we conjure up when thinking of a Category 2 hurricane.
While confidence in a turn to the north this weekend is high, there's a slim chance (as indicated by about 15% of the ECMWF ensemble members) it stays south and tracks along or near the Greater Antilles. It's just too soon to completely rule that out.  And regarding the NHC "cone of uncertainty", remember that it's designed to enclose the track of the center of the storm just 2/3 of the time, using historical errors. There's historically a 1/3 chance of it tracking outside the cone.

There is a much greater chance that Jerry will pass near Bermuda next Tuesday, not even six days after Category 3 Hurricane Humberto's visit.  This one-two punch is brutal, and actually happened five years ago when Hurricanes Fay and Gonzalo hit the island 5.5 days apart.  When the atmosphere gets stuck in a rut, watch out.

The remnants of Tropical Depression Imelda have finally loosened their wet grip from southeast Texas, and the rainfall totals are staggering.  Local amounts over 42 inches have been reported, and there is significant flooding in the Houston to Beaumont region.

Storm total rainfall estimates as of Thursday evening. https://twitter.com/JZTessler/status/1174821051550883840
This storm *barely* got a name -- it was Tropical Storm Imelda for six hours, just one single advisory on Tuesday afternoon.  That's it.  Clearly, it does not take a hurricane or even a tropical storm to cause major impacts.  But by sneaking into the "named storm" category, the potential exists for the name to be retired.  That decision would not be made until well after the season ends, and a special committee of the World Meteorological Organization convenes (think Jedi High Council).  In the following charts, I am confidently assuming that Dorian will be retired, but leaving Imelda out for now.  What stands out is that "I" storms and September storms are by far the most retired, so Imelda would certainly fit that history! This year was Imelda's first time on a list, having replaced Ingrid when it was retired in 2013.  Other "I" storms that got retired on their first use were Ike, Igor, and Irma.

Shifting our attention way east, a strong tropical wave still over Africa has a lot of support for rapid development in the model guidance. NHC is giving it a 70% chance of becoming at least a tropical depression by early next week, possibly even before reaching Cabo Verde's longitude. Specific examples from the most recent ECMWF and GFS runs are shown below (the shading is low-level cyclonic vorticity, a measure of the curvature of the wind).  The next name on the list is Karen.

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