Hurricane Zeta

[bwalk]

That's correct, they're primarily related to the cold front.

Thanks

 

[bjdeming]

Everybody here probably knows it, but I didn't understand why Zeta intensified until reading this at https://www.nola.com/news/environment/article_4a981c3c-1a36-11eb-b5e9-e7647b534e44.html

The strong trough of low pressure produced ice storms in Oklahoma and Texas on Tuesday and Wednesday while en route to the Gulf of Mexico. There, its high winds in the upper atmosphere were expected to shear Zeta's clouds and keep it at tropical storm or Category 1 status.

Instead, those winds helped draw warm air from the surface through Zeta's eye to its top, further reducing the storm’s central air pressure and helping it strengthen, senior hurricane specialist Mike Brennan said.

. . .

And as it neared Louisiana, Zeta’s forward speed increased, to almost 25 mph. That nixed another potential weakener: the cooler water along the state’s coastline. Had the storm been advancing at only 5 mph, it might have mixed cooler water from the Gulf’s depths to the surface, reducing the energy fuel that was keeping it strong, Brennan said.

By the way, is it true that Major League Baseball is considering the State of Louisiana for this year's Golden Glove Award?

 

[Kory]

The approaching trough is not always something that will shear a tropical system to pieces. That is a very antiquated and overly simplistic way to forecast storms. The NHC was correct in their initial forecast to landfall as a category 2 (Eric Blake wrote that forecast and is an up and coming met at the NHC). Then, inexplicably, the NHC reduced landfall strength and gave some boilerplate trough/shear/cooler water excuse (that was Pasch who I would remove from forecasting duties after that embarrassment). Then, Zeta continued rapid intensification up until landfall exposing an inconsistent and bewildered NHC while showing that seasonal trends of rapid intensification up until landfall continued.

I sounded the alarm to family in Louisiana when I looked at the models about 2/3 days out. Zeta was a very 2018 Michael-esque set up where the storm was moving parallel mean deep-layer flow. The approaching trough helped ventilate and cool the upper levels of the troposphere...aiding in very strong convection. It had a well established core and circulation despite spending hours over the Yucatán. It was moving so fast, the cooler waters didn’t matter. This could have been MUCH worse if Zeta wasn’t starting from a tropical storm when emerging from the Yucatán...and if it was a cat 2 like Michael when the effects of the trough started being felt.

 

[Kory]

 

[South AL Wx]

Zeta has been upgraded to a category 3 hurricane at the time of landfall (maximum winds increased from 110 to 115 mph):