Tuesday, September 25, 2018

Hurricane Watch: "Multiple Threats in the Atlantic, and a Super Typhoon in the Pacific"

First up, a quick look at the 2018 hurricane season compared to the 1981 - 2010 average using Accumulated Cyclone Energy, this version via Colorado State University.

The Pacific has seen above average activity this year while the Atlantic—our focus because of the insurance/reinsurance/cat bond/ILS aspect—has been almost exactly average, as can be seen in the graphic below the table. Click here for the interactive versions of both.

Current ACE vs Historical

And from Wunderground's Cat 6 blog (also on blogroll at right during the season):
September 24, 2018, 1:40 PM EDT
Storms are being classified and declassified at a snappy pace in the Atlantic, as several weak systems have been fighting off dry air and wind shear. We may yet see one or more of these systems strengthening as the week unfolds—and there is no question about the ferocity of Super Typhoon Trami in the Northwest Pacific (see below).
Figure 1. Saharan Air Layer (SAL) analysis for 11 am EDT September 24, 2018. Dry air (orange colors) was affecting ex-Tropical Storm Kirk, Subtropical Storm Leslie, 98L, and the remains of TD 11. Image credit: University of Wisconsin/CIMSS.
The Caribbean’s invisible wall of protection that has been present during much of the hurricane season of 2018 bashed up Tropical Storm Kirk overnight, reducing the storm to a wave of low pressure without a surface circulation. Kirk entrained some dry air overnight, and this disrupted the storm enough that it could not maintain its closed circulation, due to its fast forward motion to the west at over 20 mph. Kirk’s demise may also have been aided by the passage of a suppressed Kelvin wave, as explained in a tweet by Michael Ventrice of The Weather Company.

Satellite images early Monday afternoon showed that Kirk was growing better organized, with low-level spiral bands rebuilding and a surface circulation re-developing. Wind shear was moderate, near 10 knots, and the sea surface temperatures (SSTs) were very warm, near 29°C (84°F). It would not be a surprise to see Kirk regain tropical storm status later on Monday. In its Tropical Weather Outlook issued at 2 pm EDT Monday, the National Hurricane Center gives Kirk a 50% chance of redevelopment into at least a tropical depression through Friday....MUCH MORE