Late-season African easterly wave could become the next storm this week

Since my previous update last Wednesday, Milton made an extremely rare landfall as a Category 3 hurricane near Tampa (Sarasota)... the only previous times this was known to have happened were 1921 and 1848.  Milton was also the fifth hurricane to make landfall on the U.S. Gulf coast; the only other time there were more was in 1886 (6).  And, Leslie finally dissipated on Saturday after spending an impressive ten days as a tropical cyclone in the central Atlantic.  The season's track map spanning Alberto through Milton is shown below.

Today's post is primarily on a late-season easterly wave that exited the African coast last Thursday morning (Oct 6th) and has continued to show some signs of development.  This time of year, we don't typically see these easterly waves have much success in developing... we're normally focused much more on the western Caribbean and the Gulf of Mexico.  As you see on the map below, there is actually an area of interest brewing in the western Caribbean as well which NHC is giving a 20% chance of formation in the coming week.

But, NHC is giving the easterly wave -- tagged as Invest 94L -- a 60% probability of becoming the season's next tropical cyclone in the coming week as it heads west toward the Windward Islands.  The tracks generally continue west to west-northwest for the foreseeable future, and the intensity generally remains weak.  In some form, it will reach the Windward Islands or just north of there on Friday. I think we need to wait until it actually develops to bother looking much beyond five days.

Regarding the future disturbance in the western Caribbean, long-range model ensembles have been hinting that it will develop and then drift westward into the Yucatan peninsula then perhaps into the Bay of Campeche.

The next two names on the list are Nadine and Oscar.  Both of those names are still original from the 1982 list, so this year would be their 8th time on a list... though Nadine has only been reached three of those times (2000, 2012, 2018), and just two times for Oscar (2012, 2018). 

As of today, neither of these features look too concerning, but it's certainly worth keeping an eye on them.  The historically-active first half of October is now behind us, but even the second half has had some infamous storms, so it's way too soon to stop paying attention.

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Milton about to make catastrophic landfall in Tampa as Category 3 hurricane

As I write this at 5pm Eastern, the center of Hurricane Milton is just 65 miles southwest of Tampa Bay and it's tracking to the northeast at 17 mph.  That puts landfall at about 9pm EDT in Tampa. It is still a formidable Category 3 hurricane with 120 mph peak sustained winds as of 5pm EDT.

The center of the hurricane will pass very close to Tampa (if not directly over it), and the bay will get an extremely high storm surge if the southern eyewall passes over the bay, and much less if the northern side passes over it.  That's the difference between onshore and offshore winds.  The exact inundation depth everywhere won't be known right away, but tide gauges in the area will help with estimates at specific sites... if the tide gauges remain intact.  Between the wind and storm surge, this day will change Tampa for a very long time.

The only other analogs that come up for this occurred in 1921 and 1848, so this is unprecedented in the past century, and a LOT has changed in Tampa since 1921!

https://bmcnoldy.earth.miami.edu/tropics/radar/

A common threat with landfalling hurricanes that sometimes gets overlooked amidst the other hazards is tornadoes.  Hurricane rainbands can be prolific tornado producers, primarily in the front-right quadrant (relative to their direction of travel).  In that radar animation above, all of those red polygons are tornado warnings that were issued during the day.  Some of the observed tornadoes were unusually large and intense -- "wedges" -- which is rather extraordinary for hurricane-spawned tornadoes.

[On the topic of radar, at the link below the animation you will find the archives of Milton's coverage from Sabancuy and Cancun in Mexico, then from La Bajada in Cuba, then from Tampa.]

As I wrote previously, Milton will almost certainly end up being a retired name. It would join other recent retired "M" storms during October: Mitch (1998), Matthew (2016), and Michael (2018).  Milton was the name chosen to replace Michael, which made landfall in Florida on October 10, 2018 as a Category 5 hurricane.

Elsewhere, Leslie is actually BACK to hurricane intensity again and the other two areas of interest are still not too likely to form (30% for the one east of Florida and 10% for the one near Cabo Verde).

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Unfortunately for Florida, Milton's forecast has not changed

Milton continues its trek toward Florida, and very little has changed since yesterday's post.

Overnight, there was an eyewall replacement cycle... this is a common process that intense hurricanes go through periodically in which a larger eyewall develops outside of the original smaller one.  The smaller one decays away and the outer one becomes the only one.  During this process the storm's intensity typically decreases and the wind field expands.  Then, the new eyewall contracts, the storm re-intensifies, and another cycle may begin.  It can happen multiple times in a storm's lifetime.

As of Tuesday afternoon, Milton is a strong Category 4 hurricane and appears to be back on an intensification trend again. Tropical storm conditions are expected to reach the Florida peninsula on Wednesday afternoon, with landfall in the Tampa area late Wednesday night.  Destructive winds and storm surge will of course reach far beyond that area though.

The dire storm surge forecasts have held steady, which is not good news.  Evacuations in the affected areas should be completed by tonight.  You don't want to risk getting stuck in traffic with a major hurricane approaching. To escape storm surge, you don't need to travel very far, even a few miles is often fine if you have a safe place to stay.  Evacuations are based on water, not wind, and for good reason. 

The flooding threat from heavy rain is also extremely high through the central part of the peninsula, but then very little rain is expected in the coming days in the panhandle and down in urban southeast Florida.  Fortunately, Milton will be moving rather quickly as it crosses the state, so the rainfall totals are not uncommonly high for a landfalling tropical cyclone.  I also have a long, updating radar loop set up to monitor rainfall over the state as Milton comes through: https://bmcnoldy.earth.miami.edu/tropics/radar/

And not to throw yet another graphic at you, but this is pretty interesting: right before landfall, 

Milton's inner core will pass over some of the warmest water of its entire journey: 30-31°C (86-88°F), which is 2-3°C (3.5-5.5°F) warmer than average for this time of year.  Although some stronger wind shear should start to weaken the hurricane, it will still be very powerful and this last-minute bit of warmer water won't help.

Leslie weakened to a tropical storm on Tuesday morning after nearly six days a hurricane.  It is forecast to continue weakening and dissipate in the central Atlantic in a very uneventful fashion.

Those two areas of potential formation that I pointed out in yesterday's post are still in the outlook and are both at a 20% probability for formation within a week.

For those keeping track of Accumulated Cyclone Energy (ACE), today is actually a noteworthy day: the value accrued just surpassed the average amount during an entire average season today.  So with Leslie and Milton still active, it will continue to climb.

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