Rafael close to hurricane intensity as it approaches Cayman Islands

Since my previous post on Saturday morning, Subtropical Storm Patty did indeed pass over the Azores, then dissipated on Sunday east of the islands.  The disturbance that we've been watching for at least the past ten days was upgraded to Tropical Depression 18 on Monday morning just south of Jamaica, then to Tropical Storm Rafael on Monday afternoon.  Rafael is the season's 17th named storm.

As of Tuesday afternoon, Rafael is very close to hurricane intensity and is closing in on the Cayman Islands, then western Cuba by midday Wednesday.  It is expected to become a hurricane later today or tonight, which would be the 11th one of the season.  I have radar loops from the Caymans and Cuba at https://bmcnoldy.earth.miami.edu/tropics/radar/

Rafael will then enter the Gulf on Wednesday afternoon.  By Friday, the forecast becomes rather hazy, as there are major discrepancies among the models about what the storm will do.  In general though, it should weaken in the face in increasing wind shear and cooler water temperatures, but the track spread is noteworthy.  So, in this case, the static track cone size does not adequately capture the actual uncertainty in the 4-5-day forecast.  Thankfully, it's November and the northern Gulf is becoming relatively hostile to tropical cyclones. As of now, this does not appear to be a big heavy rain threat for the U.S. Gulf coast or inland. 

For an update on the season's activity through today, there have been 17 named storms, 10 hurricanes, and 4 major hurricanes.  The average counts by today's date are 13, 6, and 3.  The ACE is up to 126% of average for the date, or 121% of an entire average season.  Hurricane season officially ends on November 30.  If we do get another storm or two, the next names on the list are Sara and Tony.

Since the modern naming convention was introduced in 1979, this is only the 11th time (out of 46) that we reached the R name.

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Patty forms near Azores, still watching Caribbean for next storm

Since my previous post last Friday, the area of concern in the western Caribbean has still not developed into anything, but it's decidedly closer now.  This could be a threat to the Gulf coast in a week.  Elsewhere, Subtropical Storm Patty formed near the Azores on Saturday morning and will pass over the islands this weekend.  Finally, there is a tropical disturbance approaching Hispaniola and tracking west.

Starting with Subtropical Storm Patty, this is the 16th named storm of the season, and it is not expected to reach hurricane intensity.  But, it will pass directly over the Azores on Sunday bringing tropical storm conditions there.

  

By Monday, the storm will lose its subtropical characteristics and weaken, so this will not be around for very long.  The last time the Azores had a direct landfall of something was Hurricane Alex in January 2016, so it's not too common.

Next, let's go way west to the disturbance near Hispaniola.  This will unload heavy rain as it treks along the spine of the Greater Antilles.  Conditions are not too favorable for it to develop into a tropical cyclone, so it will mostly "just" be a rain-maker.  In a few days, this will likely be absorbed by the larger disturbance that's been festering in the western Caribbean for the past ten-ish days as it drifts north.

Then, we have the disturbance in the western Caribbean.  Models have been keying on its eventual development for well over a week, and now, NHC is giving it an 80% chance of becoming a tropical cyclone.  The next name on the list is Rafael.

There's finally some agreement among global models that this will develop, and track generally northward into the Gulf.  That's about where the agreement ends, but at least we have that!  The maps below show tracks from the American (left) and European (right) model ensembles out through Friday evening.  The background shading is the sea surface temperature.

The American model's ensemble is generally stronger and further east than the European's.  As far as timing goes, most members reach Cuba's latitude on Wednesday.  Then, it's too early to determine if the track will be closer to the Florida peninsula or the more likely track into the central Gulf.  Of course, once a storm is in the Gulf, it has to make landfall somewhere... there's no way out.

As far as intensity goes, a tropical storm looks very likely.  Global models tend to underestimate tropical cyclone intensity because of their relatively poorer resolution, so several of these members shown above would be at hurricane intensity.  Don't look closely at specific tracks as they inevitably shift around, but you get a sense of the likely track and intensity.

This disturbance will be sitting over the western Caribbean for the next four days or so, and the water is *extremely* warm.  The ocean heat content averaged over the Caribbean is near-record high, nearly tied with 2023, which was far above any other previous year.  The same goes for the sea surface temperature.

Hurricane season ends in four weeks, so we need to still be watching things closely, especially in an active season like this with crazy-warm ocean temperatures still lingering everywhere.

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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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