22 September 2020

Beta makes landfall, Teddy heads for Canada, Paulette is back


Tropical Storm Beta made landfall in Port O'Connor, Texas on Monday night and as anticipated, the wind and the storm surge were not a big deal, but the rain was, and still is. Here is a three-day rainfall accumulation estimate (there's also a regional radar loop going back to the 19th at bmcnoldy.rsmas.miami.edu/tropics/radar/) showing the not-too-impressive-looking storm and its stagnant sprawling rain. Beta is already the NINTH named storm to hit the continental U.S. this year... tied with 1916 for the most in an entire season.


Beta is forecast to continue to sit in roughly the same area for another day or so before getting kicked off toward the northeast. This will result in more rain over the same general areas, so flash flooding is of course a significant hazard.


Hurricane Teddy passed east of Bermuda on Monday (exactly a week after Hurricane Paulette passed directly over the island) and is making the transition to an extratropical cyclone... but it's still technically a Category 2 hurricane and is rapidly headed for Nova Scotia at 30 mph. The wind field is large, with tropical storm force winds extending up to 350 miles from the center, and hurricane-force winds as much as 105 miles from the center. This will be a very impactful storm there and in Newfoundland, both in terms of wind and storm surge. The last few hurricanes to make landfall in Nova Scotia were Dorian (2019), Earl (2010), Kyle (2008), and Juan (2003).

Fifteen days after it first formed, eight days after passing over Bermuda, and six days after it was declared to be extratropical, Paulette is back as a tropical cyclone. Located between the Azores and the Canaries, Tropical Storm Paulette is now stuck in an area with very weak steering currents, so it should be around for a few more days, basically in the same spot.  It is not expected to strengthen much, but it's enough of an oddity to fit in well with the rest of the odd season.


Finally, there's a small disorganized disturbance that formed along a frontal boundary over the weekend... it's centered over western Cuba and south Florida, and is not forecast to move much. Development is very unlikely, but it will make for some breezy and rainy conditions in the region for a day or two. In the infrared satellite image at the top of the post, it's hard to distinguish it amidst the rest of the active front draping down from Teddy.

With the surge of activity lately, the ACE (Accumulated Cyclone Energy) has jumped up to about 147% of average for the date. But it still doesn't touch the values from some of the mega-seasons of the past through September 21 -- the top five through this date are 1933, 2004, 1995, 1926, and 2017.


Elsewhere across the basin, things look quiet for the foreseeable future. But when the time comes, the next names on the list are Gamma and Delta.


19 September 2020

Now two names into the Greek list, and watching five storms

For the first time since 1893, THREE named storms formed in one day: Wilfred, Alpha, and Beta. When I started writing yesterday's blog post, Wilfred had just formed. Shortly after publishing it, Alpha formed, and a few hours later, Beta formed. I certainly can't recall anything like this happening in my 25 years of writing these posts! And to keep it even more interesting, Teddy's still a Category 4 hurricane and ex-Paulette is still out there and has a decent chance of re-developing.


Rather than discussing these in alphabetical order, I'll start west and go east. Tropical Depression 22, which had been festering for a long time in the western Gulf of Mexico, was upgraded to Tropical Storm Beta on Friday afternoon.  It is forecast to intensify to the season's ninth hurricane shortly as it drifts northwest toward Texas. The map below shows the NHC forecast track, the various tropical storm/hurricane watches and warnings, and the probability of tropical storm force winds.


But the hurricane part isn't the problem... it's the drifting. Models have been indicating that Beta will stall near the Texas coast and produce tremendous amounts of rainfall in the coming days.  It's essentially a toned-down version of Harvey in 2017 (that was a Category 4 hurricane at landfall and then stalled further north for several days). There's still uncertainty in the track of course, so the exact placement of rainfall maxima is impossible to know this far out, but a large swath of eastern Texas and Louisiana should be preparing for significant flooding.


On to Teddy... tropical storm warnings have been issued for Bermuda as the Category 4 hurricane approaches.  Teddy will pass east of the island and spare it from a second major impact in one week, but tropical storm conditions are possible as it zips by on Monday. But then, there's strong agreement among models that it will slam into Nova Scotia on Tuesday, possibly still with hurricane-force winds (even if it's technically not a hurricane anymore).


As expected, Tropical Storm Wilfred is battling a hostile environment and will likely not be around much longer. It's very disorganized and should dissipate by Sunday or Monday. This is something that might seem strange: a dissipating tropical storm in the heart of the deep tropics in mid-September. This fits in with what I'll discuss at the end of the post: lots of storms but they don't last long.


Moving on to Subtropical Storm Alpha, which made landfall on Portugal's coast on Friday night and has since weakened. This formed from an extratropical low pressure system that NHC began watching for development last Monday night, so it certainly didn't come out of nowhere, but the uncertainty was around whether or not it would acquire subtropical or tropical cyclone characteristics before reaching land -- it did, briefly. As a result, it got named, and Portugal got to usher in the use of the Greek alphabet for Atlantic storms this year.


And finally, we're still keeping an eye on what was Hurricane Paulette.  This isn't too surprising though, as many models had been suggesting that it would make a sharp turn to the south and return to warmer waters and possibly regain tropical cyclone characteristics. The turn happened, but the tropical transition has not happened yet. It's presently near the Azores, and has tropical storm-force winds. It also has a lot of smoke from the California wildfires wrapping into the circulation, which shows up here as the milky colors.


Don't believe me?  Using NOAA's HYSPLIT model, here's a backward trajectory that I calculated starting at Paulette's present location and going back eight days... the smoky air wrapping into Paulette came directly from southern California.


Wilfred, Alpha, and Beta are the season's 21st, 22nd, and 23rd named storms, which puts this season an incredible 33 days ahead of 2005's record pace. But, 12 of the 23 named storms this year were around for three days or less, and only 2 of the 23 were major hurricanes (Laura and Teddy).

So in terms of ACE (Accumulated Cyclone Energy), the average ACE per storm through today in 2020 is 3.8, while at this point in 2005, it was 8.7.  And at this point in 1933, the average ACE/storm was 15.2!

In fact, 2005 isn't even in the top five ACE producing years as of today... the top five are 1933, 1995, 2004, 1926, and 1950. But as of September 19, the ACE is 136% of average for the date -- a big spike after being near-average just a week ago. As you can see below, it's really comparable to 2018 and 2019 as of today.

18 September 2020

Wilfred and Alpha form in eastern Atlantic

For only the second time in history, the list of Atlantic tropical cyclone names has been exhausted. The wave in the eastern Atlantic was upgraded to Tropical Storm Wilfred on Friday morning.  This is the 21st named storm of the season, and is now three *weeks* ahead of 2005's record pace.


In the near term, Wilfred is expected to strengthen just a bit more, but then environmental conditions should become rather hostile by Monday, and the official forecast actually shows it dissipating in the deep tropics over the central Atlantic early next week.


Teddy has continued to intensify and is now a powerful Category 4 hurricane.  It's headed in the general direction of Bermuda, and should pass just east of the island on Sunday night.


Beyond the Bermuda encounter, it appears very likely that it will impact Nova Scotia as a strong hurricane (or extratropical cyclone with hurricane-force winds) on Tuesday.  The last few hurricanes to hit Nova Scotia were Dorian (2019), Earl (2010), Kyle (2008), and Juan (2003). 


Surprisingly, a low pressure system off the coast of Portugal developed today too, and is now Subtropical Storm Alpha.  This is the 22nd named storm of the season, and thus the first one to use the Greek alphabet! This won't around very long, but it certainly is interesting... the last subtropical storm to hit Portugal was Leslie in 2018.


We are also really close to having Tropical Storm Beta in the western Gulf of Mexico.  It's currently Tropical Depression 22, and models have been trending stronger.  The NHC forecast brings it up to hurricane intensity on Sunday and Monday as it drifts north, but then *possibly* weakening back to a tropical storm on Tuesday as it nears the Texas coast and slows to a crawl.


Unfortunately, regardless of just how intense it gets in the coming week, the rainfall will be very significant: this map below shows the rainfall forecast through next Friday. The sluggish motion will allow it to rain over the same locations for days.


Elsewhere, there is not much worth monitoring at this time.