Déjà vu: watching the western Caribbean again for potential development next week

Models have been hinting at something developing in the western Caribbean for a few days now, and the time and place fits in well with climatology. The next name on the list is Patty.

This map below shows the historical formation locations during the first ten days of November, and the western Caribbean certainly stands out as a hot spot.

Tracks of low pressure systems from the American (left) and European (right) model ensembles are shown below out through the next ten days.  The European model ensemble has not done so well with genesis this year, so I'd put much more weight on the more bullish American model's ensemble.

That one shows development of a coherent low pressure system on Tuesday-Wednesday next week, then a general track toward the north with some intensification.  The spread in solutions becomes quite large even in one week (next Friday), so it's too soon to speculate about what happens beyond that.

What we can learn from this is that there is a consistent signal in the models for something to develop in the western Caribbean by next weekend.  We will need to watch this closely because conditions are more than ample to support a strong hurricane.  The ocean heat content averaged over the Caribbean is still near-record high and far above any other year except for 2023.

It's important to not let our guard down at this late point in hurricane season... it's not over yet.  There is no shortage of examples of November hurricanes -- just in the last 25 years there have been 17 of them, including 6 major hurricanes: Lenny (1999), Michelle (2001), Paloma (2008), Otto (2016), Eta (2020), Iota (2020).

There have been 7 names retired from November hurricanes: Lenny (1999), Michelle (2001), Noel (2007), Paloma (2008), Otto (2016), Eta (2020), Iota (2020).

Notice something about those two lists? All six major hurricanes that occurred during November over the past 25 years were impactful enough to have their names retired. Hopefully whatever comes of this system of interest does not get added to that list.

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Nadine and Oscar form over the weekend

Since my previous post a week ago, the two systems I discussed did become named storms.  The disturbance in the western Caribbean became Tropical Storm Nadine on the morning of the 19th, then made landfall in Belize and dissipated a day later.

Much more impressively, the wave I mentioned in that post, Invest 94L, finally developed north of the Dominican Republic.  It left the African coast on October 10, and as of 5am EDT on Saturday the 19th it had a 30% chance of formation according to NHC.  They increased that to 60% at 8am, then at 11am it was upgraded to Tropical Storm Oscar.  Amazingly, at 2pm it was upgraded again to a hurricane.  The peak winds increased from 40 to 80 mph in just three hours, and 40 to 85 mph in six hours.  This was all from data collected by aircraft reconnaissance.

For posterity, I have a 12-hour satellite loop below, spanning 8am-8pm EDT on October 19.  This captures the formation of both Nadine and Oscar, as well as Nadine's landfall and Oscar's rapid intensification.

This explosive intensification occurred near the Turks and Caicos Islands as it was headed for the eastern tip of Cuba.  Since making landfall in Cuba it has weakened to a tropical storm but is producing extremely heavy rainfall as it stalls prior to an anticipated northward turn.  It is not forecast to regain hurricane intensity as it heads toward Bermuda by the end of the week.

Oscar is one of the more notable examples in recent memory of model failure to capture genesis and then intensification even at extremely short lead times.  It was also really tiny.  James Franklin, former head of the Hurricane Specialist Unit at NHC, wrote this on Sunday: "Up until Oscar, no storm had a largest R64 of less than 10 n mi.  I believe that makes Oscar (R64=5 n mi) the smallest hurricane we know of."

There is nothing else of interest in the coming week, so after this rapid-fire development of the 14th and 15th named storms, things will slow down.  We still have 40 days remaining in hurricane season, so we still need to be paying attention though.

For an update on seasonal activity to-date, there have been 15 named storms, 10 hurricanes, and 4 major hurricanes.  The average in a full season is 14, 7, and 3.  In terms of ACE, that's at about 131% of average for the date.

There have been two Category 5 hurricanes so far (Beryl and Milton) which is extraordinary -- the other seasons with 2+ known Category 5s were 2017, 2007, 2005, 1961, 1933, and 1932.  

Of the 15 named storms, 10 of them made landfall somewhere.  All of this combines to put 2024 way toward the top end of hurricane seasons.

 

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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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Milton explosively intensifies in western Gulf, warnings issued for Florida

In one of the most explosive rounds of intensification in recorded history, Milton's peak winds increased from 90 mph at 2am EDT on Monday to 175 mph at 2pm then 180 mph at 5pm.  It went from a Category 1 to a Category 5 hurricane in just nine hours.  This satellite animation reveals the minimal vertical wind shear as evident by the thin whispy ice clouds drifting around as well as a pinhole eye that is just 8 miles in diameter.  Record warm water temperatures also played a big role in facilitating this.

With 180 mph peak winds, there have only been five other Atlantic hurricanes that had higher peak intensities: Allen 1980 (190),  Labor Day 1935 (185), Gilbert 1988 (185), Dorian 2019 (185), and Wilma 2005 (185), There have been three others that tied the 180 mph mark.

The storm's intensity and central pressure were very well measured throughout the day by multiple reconnaissance flights by both NOAA and the Air Force.  It has also been in radar range from Sabancuy, Mexico, and its tiny and intense inner core shows up very well from there too.

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

As of 5pm EDT on Monday, Milton is a Category 5 hurricane (the season's second) located just north of the Yucatan peninsula.  It still has two more days over water until it reaches the Florida peninsula on Wednesday evening.  Those peak winds will decrease somewhat as wind shear picks up closer to landfall, but that absolutely does not diminish the threat it poses. Any preparations and evacuations across Florida should be well underway and wrapped up ASAP, or at the latest, before Wednesday morning when tropical storm conditions could arrive.

The storm surge forecasts for the Tampa area and surrounding coastline are catastrophically high, with 10-15 feet possible in the central part of the peninsula.  Do not hesitate any longer to evacuate if told to -- this is as dire as it gets.

The afternoon suite of HTI graphics is shown below and you can always find the most recent at https://www.weather.gov/srh/tropical#hti which are zoomable and interactive.

Also, don't forget that the Florida peninsula is skinny -- the hurricane will quickly cross over to the east side, bringing hurricane conditions and dangerous storm surge there as well.

Milton will undoubtedly join other October "M" Category 5 hurricanes in retirement: Mitch (1998), Matthew (2016), and Michael (2018).  Milton was actually the replacement name for Michael in this list.

And just to keep tabs on Kirk and Leslie, Kirk has transitioned to an extratropical cyclone and will reach northern France on Wednesday, while Leslie is still maintaining hurricane intensity in the central Atlantic.  It is forecast to weaken this week and be out of the picture this weekend.

Elsewhere across the basin, there's an easterly wave still over Africa that NHC is giving a 30% chance of formation once it exits the continent, and a disturbance near south Florida with a 10% chance as it heads toward the northeast.

 

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Dire days ahead for Florida as Milton intensifies

Milton is still a tropical storm in the western Gulf of Mexico as of late Sunday morning, but is very close to reaching hurricane intensity.  It will track eastward across the Gulf of Mexico and reach the Florida peninsula late Wednesday; however, significant impacts will begin before that.

Overlay of all five track forecast cones from NHC spanning when TD14 first formed on Saturday morning through late Sunday morning.  The cone only represents where the center of the storm may track with 2/3 probability; it does not show where impacts will be experienced.

The forecasts from the models and NHC have been fairly stable (not varying much from run to run), which continues to paint a dire picture for many parts of already-storm-ravaged western Florida.  There is strong agreement on a track toward the central part of the peninsula, with a landfall late Wednesday, and at an intensity of at least a Category 3 hurricane.

Not only is there relatively light vertical wind shear in the Gulf right now, the water temperature is still record-breaking warm.  And it's not just warm in terms of the sea surface temperature, but also through a depth as measured by ocean heat content.  High ocean heat content provides a hurricane with a constant source of fuel and makes it much harder to upwell cooler water from below which could weaken the storm.  This will help Milton to rapidly intensify and reach a higher peak intensity.

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

The Sunday 11am forecast from NHC brings it to nearly Category 4 intensity at landfall on Wednesday afternoon/evening.  There is too much uncertainty to know exactly where landfall will be, but forecasts have been focused between Tampa and Fort Myers.  For most hazards, the exact landfall location doesn't matter, but for peak storm surge it does. There is a world of difference between being just north of the eye with offshore winds and just south of the eye with onshore winds.  Prepare assuming you're going to be on the bad side.

Preparations should be completed by the time tropical storm conditions could arrive, which for this storm looks like early Wednesday morning along much of the peninsula.

In addition to the devastating wind and storm surge impacts from a forecast like that, the entire peninsula is already experiencing widespread heavy rain today and that will continue until the hurricane passes through on Thursday morning. The map below shows the five-day outlook of flash flood risk.

It's still slightly too early get watches and warnings for Florida, but they could start being issued as early as Sunday evening, certainly by Monday morning. Be prepared to see storm surge warnings with ominous peak values on parts of the west coast of the peninsula.  Many of these areas are still cleaning up after Helene's storm surge, but this is very likely going to be worse.  Don't wait to leave if told to.

Elsewhere, Kirk and Leslie are still both hurricanes in the central Atlantic.  Leslie will weaken before reaching any land, but Kirk is still forecast to reach northern Europe on Wednesday.  As I brought up several times before, it will most likely not be technically "tropical" by then and it will weaken relative to what it is now, but impacts from wind and storm surge will still be felt.

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Kirk and Lesie are both hurricanes, Milton forms and threatens Florida

Kirk is still a major hurricane, presently at Category 3 intensity; Leslie was upgraded to the season's 8th hurricane on Friday night, and Tropical Storm Milton formed in the western Gulf of Mexico... it's very busy out there.

Very little has changed with the forecasts for Kirk and Leslie: Kirk is still expected to bring dangerous conditions to the British Isles and France on Wednesday.  Leslie is tracking right behind Kirk but has probably peaked in intensity and is forecast to weaken in the coming days, not posing a threat to land.

As I've mentioned for a while, swells generated by Kirk will spread across the Atlantic and reach the U.S. east coast beginning Sunday... definitely something to be alert for particularly near high tides when coastal flooding is more likely.

Moving on to Milton, this has been a long-festering system in the western Caribbean and Gulf, which I first wrote about on September 27.  It was upgraded to Tropical Depression 14 on Saturday morning and then Tropical Storm Milton just a few hours later.  This is the 13th named storm of the season, and is almost certainly going to become the 9th hurricane.  (Milton is a new name on this list, replacing Michael which was retired after the 2018 season.)

Milton is located in the far western Gulf, near the coast of Mexico, and is forecast to start moving east tomorrow.  Then, fairly low wind shear and exceptionally warm water should allow the storm to intensify very quickly before reaching the Florida peninsula on Wednesday, perhaps as a major hurricane as the forecast below shows.

Remember the track forecast cone only shows an area where the center of the storm might go with 2/3 probability (1/3 chance it tracks outside the cone)... and most importantly, the cone DOES NOT show impacts which are definitely not limited to the bounds of the cone.  It's too early for watches and warnings to be issued for Florida, but when they are, the wind-related ones will be shown on the cone map, and the storm surge ones will be shown on a separate map.

Furthermore, the Florida peninsula is thin.  When a hurricane makes landfall on one side, it doesn't have a long trip to pass over to the opposite coast, so the east coast of the Florida peninsula should also be preparing for a hurricane.

As has been the case all along, the threat of multiple days of heavy rain will create problems with widespread flooding across Florida.  The graphic below shows the current rainfall outlook for the next week.

Milton will almost certainly be the 5th hurricane landfall on the US Gulf coast this year (and the 3rd just in Florida).  From my searching, it looks like there were 5 US Gulf coast hurricane landfalls in 2020 and 2005 and there were 6 in 1886.  So this is way up there in terms of rarity of impacts.

 

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Hurricane Kirk strengthens, Tropical Storm Leslie strengthens, Gulf still unsettled

I intentionally mimicked the post's title from two days ago because almost nothing has changed since then.  Kirk has intensified more as expected, becoming the season's 3rd major hurricane on Thursday (it's not impossible that it clips Category 5 intensity today).  TD13 was upgraded to Tropical Storm Leslie on Wednesday night and it's still following in Kirk's footsteps. And, the mess in the Gulf of Mexico is still a mess with a very uncertain future.

On Friday morning, Kirk is a Category 4 hurricane located about 1000 miles northeast of the Windward Islands.

It will remain over the open ocean for the next 5-6 days and then will approach the British Isles and northern France where fairly major impacts are expected.  It may not technically be classified as a hurricane anymore by then, but it will still be a potent extratropical cyclone bringing destructive winds, heavy rain, and huge surf on Thursday-Friday of next week... similar to Lorenzo in October 2019.

As I pointed out on Wednesday morning, the wave field from Kirk will spread throughout the Atlantic, reaching the U.S. east coast on Sunday, resulting in elevated high tides and increased risks of coastal flooding and erosion.

Tropical Storm Leslie is also forecast to remain in the central Atlantic, and follow right behind Kirk, with a five-day lag.  It should reach hurricane intensity this weekend, and possibly major hurricane intensity early next week.

Then, there's the broad disturbance in the Gulf of Mexico that we've been watching since at least last Thursday. There's not much to look at right now, but NHC is giving it a 40% probability of becoming a tropical cyclone within a week, and the models are still pretty scattered about what to do with it.  

There's general agreement that it will begin to drift east toward the Florida peninsula, with rainfall beginning on Sunday and lasting for days.  It could develop into a tropical or subtropical depression or storm by then, but wind will not be the primary hazard from this; it will be rain.  Several models are now showing a weak low pressure center over south or central Florida on Tuesday into Wednesday, possibly a low-end tropical storm.  The next name on the list is Milton.

The WPC's latest 7-day rainfall forecast is shown below, and it will evolve, but the entire peninsula should be paying attention to this in the coming days -- not just for the flooding potential, but the small chance that it intensifies more than models are currently showing.

For an update on the season's Accumulated Cyclone Energy, through today the 2024 season is at about 95% of average and climbing.  It will cross back above average this weekend.  In terms of storm counts, we've now had 12 named storms, 7 hurricanes, and 3 major hurricanes.  The average number by this date is 11, 5, and 2.

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