Sally intensifies into a dangerous hurricane » Yale Climate Connections


On Monday, for just the second time on record, the Atlantic has five simultaneous hurricanes, tropical storms, and tropical depressions, as Hurricane Paulette, Hurricane Sally, Tropical Storm Teddy, Tropical Storm Vicky, and Tropical Depression Rene all roamed the waters.

Colorado State University hurricane scientist Phil Klotzbach says the only other time five simultaneous tropical cyclones existed in the Atlantic was September 11-14, 1971. The record is six, set during the period September 11-12, 1971: Edith, Fern, Ginger, Unnamed, Heidi and Irene.

Just four days after the climatological midpoint of the Atlantic hurricane season, we’ve had 20 named storms so far in 2020, an astounding level of activity has been exceeded only once … and then during an entire season: in 2005, when 28 named storms formed.

At 12:30 p.m. EDT Monday, September 14, Sally was centered 165 miles southeast of Biloxi, Mississippi. Sally was a strengthening hurricane with 90 mph winds, moving west-northwest at 7 mph with a central pressure of 985 mb. Wind gusts as high as 66 mph were observed late Monday morning at the VK 786/Petronius (Chevron) oil rig offshore from Mobile, Alabama (elevation 53 feet).

Sally was bringing heavy rains to the Florida Panhandle and to the Alabama coast on Monday. On Sunday, Sally brought more than five inches of heavy rains to portions of the Florida west coast, after deluging the Florida Keys on Saturday with 11.36 inches at Key West and 11.99 inches at Lower Matecumbe Key.

Satellite and radar images showed a sharp increase in the intensity of Sally’s heavy thunderstorm activity on Monday morning, with the surface center of circulation reforming to the east under the most intense thunderstorms, allowing the storm to become vertically aligned. Moderate wind shear of 10-20 knots from upper-level winds out of the west continued to interfere with heavy thunderstorm formation on the west side of Sally’s circulation. However, radar imagery showed Sally in the process of closing off an eyewall, and once that process is complete, the wind shear will have less of an impact and more rapid intensification can occur.

Satellite imagery late Monday morning appeared to show a pattern called a Central Cold Cover (CCC), with a single large thunderstorm dominant. Typically, the huge thunderstorm when a CCC pattern is present is anchored to the arm of a low-level rain band some distance outside of the storm’s core; in that case, development is typically slowed until the large thunderstorm goes away (kudos to Boris Konon and Mark Lander for pointing this out). Usually, a storm is at an intensity of about 55 – 65 mph when a CCC occurs, though that intensity can happen at any stage of development. It is possible that this CCC structure may be able to slow Sally’s intensification.

The track forecast for Sally has more uncertainty than usual for a storm expected to make landfall in less than 48 hours. Sally is forecast to move in a general west-northwest motion at about 6 – 7 mph through Monday night. Steering currents will weaken by Monday night, causing a slowdown of Sally’s forward speed to 5 mph or less, as the storm begins to feel the influence of a strong band of upper-level west-southwesterly winds over the southern U.S.

A weakness in the ridge of high-pressure steering Sally should allow the storm to turn north by Tuesday morning, when Sally will be very close to the coast. The timing of this turn will strongly depend upon how quickly Sally organizes and intensifies. A stronger storm will be affected more by the upper-level winds, which are blowing from the west, forcing a quicker turn to the right and resulting in a landfall in Mississippi or Alabama. A slower-organizing storm is more likely to make landfall in Louisiana, at a lower intensity. With Sally now a hurricane, a turn more to the right and landfall in Mississippi or Alabama appears most likely.

Wind shear may decrease to around 10 knots by Monday night, which will potentially allow Sally to completely close off a center and finish building an eyewall. The air mass surrounding Sally is reasonably moist, with a mid-level relative humidity around 65%, so dry air is unlikely to be a major hindrance to this process.

By Tuesday morning, wind shear is expected to tick up a notch, to around 20 – 25 knots, which may slow or halt the intensification process. This shear will be caused by the strong band of upper-level westerly winds helping steer Sally more to the right, as mentioned above. This band of winds will also ventilate Sally, though, providing an upper-level outflow channel capable of aiding intensification.

Sally will be over the very warm waters of the northeastern Gulf of Mexico, where sea surface temperatures are around 29.5°C (85°F). There is plenty of heat energy in the ocean waters Sally will be traversing to support rapid intensification, as the storm should remain just northeast of a cool eddy with low oceanic heat content over the southeast Gulf.

How much Sally strengthens will depend in large part on how quickly it closes off an eye; a period of rapid intensification cannot be ruled out if the storm organizes quickly enough. The 12Z Monday run of the SHIPS model gave a 16% chance that Sally would rapidly intensify by 30 mph in a 24-hour period, and an 11% chance it would intensify by 50 mph in 36 hours. Sally was just shy of meeting that 16% chance of intensifying 30 mph in 24 hours, since it intensified by 25 mph between 8 a.m. and 12:30 p.m. EDT Monday.

The official forecast calls for Sally to peak as a category 2 hurricane with winds of 105 mph, but it could reach category 3 hurricane strength with 115 mph winds if it manages to close off a complete eyewall by Tuesday morning.

Regardless of its landfall intensity, the primary damage from Sally is likely to result from the slow-moving storm’s torrential rains. Sally is expected to move at 6 mph or less through Thursday, leading to rainfall measurements in feet rather than in inches. Models suggest that localized totals in excess of two feet are possible. A larger corridor of 8-16 inches can be expected near the coasts of southeast Louisiana, Mississippi, Alabama, and the extreme western Florida Panhandle.

Storm surge is also a major concern, with up to 11 feet of surge predicted along the east side of New Orleans. As discussed in Sunday’s post, New Orleans’ rebuilt levee system has proven it can handle storm surge flooding of at least 17 feet, the peak level of storm surge flooding observed during Hurricane Isaac in August 2012. However, many areas outside this levee system are not as well fortified and suffered destructive storm surge flooding during Isaac. Sally is likely to produce a prolonged and dangerous storm surge from Monday into Wednesday across far southeast Louisiana, Mississippi, Alabama, and far western Florida.

Trabus Technologies maintains a live storm surge tracker for Sally. As of 3 p.m. EDT Monday, the peak surges measured at NOAA tide gauges from Sally were:

3.2 feet at Shell Beach, Louisiana (southeast of New Orleans)
2.7 feet at Apalachicola, Florida
2.6 feet at Waveland, Mississippi
2.4 feet at Panama City Beach, Florida
2.3 feet at Cedar Key, Florida

Hurricane Paulette made a direct hit on the island of Bermuda early Monday morning, with its 40-mile-wide eye encompassing almost the entire island at 5 a.m. EDT. At landfall, Paulette was a category 1 hurricane with 85 mph winds. The hurricane’s winds increased to 90 mph while Bermuda was in the eye; at 9 a.m. EDT, when the rear eyewall was pounding the island, NHC upgraded Paulette to a category 2 hurricane with 100 mph winds.

An island-wide outage knocked out power to 20,000 customers on Bermuda at approximately 1 a.m. EDT, but the Government of Bermuda reported via Twitter at 8 a.m. that the island had experienced “no major issues” during passage of the front eyewall of Paulette. With its years of hurricane experience, Bermuda is well-fortified against storms such as Paulette.

Peak winds reported by the Bermuda airport during passage of Paulette were 55 mph, gusting to 89 mph, but the station did not report a 4 a.m. EDT observation, when the most intense part of Paulette’s eyewall was overhead. Between 2 – 3 a.m. EDT, an observing station at the National Museum of Bermuda reported sustained winds of 62 mph, with gusts up to 96 mph. A weather station in Wreck Road, Bermuda, reported a sustained wind of 80 mph and a gust to 107 mph around 10 a.m. EDT.

With conditions for intensification favorable, Paulette is expected to become a high-end category 3 storm with 125 mph winds on Tuesday, becoming the Atlantic’s second major hurricane of 2020. Increased wind shear and cooler waters will begin a weakening trend on Wednesday. (Note that by the time the hyperactive 2005 season got to the “P” storm, Philippe, that season had already produced four major hurricanes.)

Far to the southeast of Paulette, slow-moving Tropical Depression Rene was on its last legs Monday. Top sustained winds were a mere 30 mph, and strong wind shear was pushing dry air into the tiny system. Rene will likely become a remnant low by Tuesday.

Tropical Storm Teddy, which formed in the central Atlantic on Monday morning, was headed west at 14 mph at 11 a.m. EDT Monday with top sustained winds of 40 mph. Teddy is expected to turn to the northwest on Wednesday, well before reaching the Lesser Antilles Islands.

Conditions for intensification will be very favorable late this week, and Teddy is predicted to be a major hurricane by Friday. Bermuda and Newfoundland, Canada, may potentially be at risk from Teddy.

Tropical Storm Vicky formed in the eastern Atlantic at 11 a.m. EDT Monday, about 350 miles west-northwest of the Cabo Verde Islands. Vicky was headed northwest at 6 mph, with top sustained winds of 45 mph. Vicky will have favorable conditions for development through Monday night, with sea surface temperatures near 26.5 Celsius (80°F), moderately to high wind shear of 20 – 25 knots, and a moist atmosphere. However, wind shear is predicted to rise to a prohibitively high 40 – 60 knots Tuesday through Wednesday, destroying Vicky by Thursday. Vicky is not a threat to any land areas.

A new tropical wave, emerging from the coast of Africa on Monday, has some modest model support for development late in the week as it moves west at about 10 mph. Two of the 51 members of the 0Z Monday European model ensemble forecast showed this system would develop into a tropical storm that would reach the Lesser Antilles Islands by Tuesday, September 22.

In its 2 p.m. Monday EDT Tropical Weather Outlook, NHC gave this wave two-day and five-day odds of development of 20% and 50%, respectively. The next name on the Atlantic list of storms is Wilfred — the last name on the list.

NHC on Monday was monitoring an area of interest over the western Gulf of Mexico producing a few disorganized showers and thunderstorms. Some slow development is possible while this system moves southwestward at 5 – 10 mph over the western Gulf of Mexico this week.

Dry air over the western Gulf of Mexico, however, is likely to inhibit its development, as will wind shear. In its 2 p.m. EDT Monday Tropical Weather Outlook, NHC gave this system two-day and five-day odds of development of 10% and 20%, respectively.

Teddy’s arrival on September 14 marks the earliest date that any Atlantic season has produced its nineteenth tropical storm, topping the record held by an unnamed storm from October 4, 2005, which was classified after the season was over. Vicky’s arrival on September 14 marks the earliest date that any Atlantic season has produced its twentieth tropical storm, topping the record held by Tammy from October 5, 2005.

With the Atlantic hurricane season just four days past the climatological half-way point, we’ve already had 20 named storms, seven hurricanes, and one intense hurricane. Only two Atlantic hurricane seasons since 1851 have had that many named storms, and both of those during an entire season. The record was 28 named storms in 2005, followed by 1933, with 20 named storms. According to Colorado State University hurricane scientist Phil Klotzbach, the averages for this point in the season are seven named storms, three hurricanes, and 1.5 intense hurricanes.

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Upper level winds pushing from the west against the mid and lower level winds currently……Sally appears to be stalling some…..

“Weird” (or at least weird to me) storm motions via New Orleans and Mobile radars. Main rain shield erodes abruptly in northwest quad. just beyond that, storms track appears almost linear from northeast to southwest where you would expect them to re-curve relative to Sally’s center (also apparent on radar). Wish I could post a loop here to show what I am talking about.

It’s not dead in here I read everything you all discuss as do others, I don’t know how I would handle a hurricane season without all of you and Jeff & Bob. Thank you

Wow, after some REALLY impressive convection earlier today, Sally certainly appears to be changing quickly this evening in satellite imagery. Is dry air being pulled into the storm resulting in an almost extratropical appearance?

Seeing that too. So glad. It has nearly been stalled out in the last 3 hrs.

BULLETINHurricane Sally Intermediate Advisory Number 14ANWS National Hurricane Center Miami FL AL192020700 PM CDT Mon Sep 14 2020



A Storm Surge Warning is in effect for…* Port Fourchon Louisiana to the Okaloosa/Walton County Line Florida* Lake Pontchartrain, Lake Maurepas, and Lake Borgne* Mobile Bay

A Hurricane Warning is in effect for…* Morgan City Louisiana to the Navarre Florida* Lake Pontchartrain and Lake Maurepas including metropolitan NewOrleans

A Tropical Storm Warning is in effect for…* East of of Navarre Florida to Indian Pass Florida

If you look at the satellite picture only 3 systems are worth mentioning, the other ones are just swirls

Donald Trump on the West Fires today, “It’ll get cooler, just you watch”. Evil mocking at the loudest levels possible. No one in our Nation should be okay with any of this.

He also said this: “Trees only live about 18 months before they dry out and explode. And leaves just lay there on the ground for years, like matchsticks.”

“When trees fall down after a short period of time they become very dry — really like a matchstick… and they can explode. Also leaves,” Trump said

Gee you want to knock the guy ok. He gives you ample opportunity so at least get it correct. No need to distort

Thanks for the clarification. It’s just he is capable of saying something as asinine as that.

I do believe he actually did say this, “You go to Europe… They’re very, very strong on management, and they don’t have a problem. They really don’t have, with, as they say, more explosive trees than we have in California.”

Don’t worry, most decent people feel and share your rage. I hope a jail bar future is in the works for him, Can always hope. He is a Despotic POS in the worst way. Stupid as well. His niece ought to be on more talk shows.

A regular Al Roker, Trump is. “It’ll get cooler, just you watch”. Yep, it’s called winter. It’s bound to show up at some point.

Climate deniers are so wrong their ignorance is pitiful. Climate changes regardless of decade or century. The world will heat, and it will cool no matter what we do. We need to appreciate nature for providing humanity a zone where we can survive and thrive to the best of our abilities. Thanks to the NHC and NOAA for providing timely information to plan accordingly.

I am starting to get the feeling that nature’s intent was to get us right where it wanted us, then… BAM!

From the NHC. Note the likely Cat 3. Will this go over NO or just miss it. Filling in the w side now.

I am really thankful for the NHC and our public servants in general whether they be public health, police, public safety, disaster management, etc. I’d say more, but it’s not the time.

Anyway, just got my latest hurricane warning on my phone from the NHC. It ended with ‘FOLLOW INSTRUCTIONS FROM LOCAL OFFICIALS.’ Kind of sad that they have to say that….

Notice the 100 mph winds, and dropping pressure. Bad new for sure. Rain by the foot? Close to or over NO. I feel like we are being told something and just not listing or possibly understanding. I see us moving away from oil rather quickley.

Of course it is dangerous, but its the least dangerous classification of Hurricane that is possible. Why pretend it’s something bigger?

The category rating only depends on wind speed and doesn’t take into account rain and/or surge which seem to be the bigger issues for this storm considering how slowly it is moving.

It is now 100 mph winds and pressure dropping. Not the best place to be making landfall either.

Far more people die due to surge/flooding than wind. In fact, if you add up all the deaths from Tropical Storms vs. Hurricanes in the Atlantic basin, I’m guessing you might be surprised. Lots of people die, particularly south of the US border with Mexico, in Tropical Storms.

Allison was “only a tropical storm”. Agnes was “only a Cat 1”. Heck, Sandy wasn’t even a tropical system! Why bother?

Radar makes me think she is about to slow and/or shift to a more northerly track.

Anyone know where everyone from cat 6 blog went? Is there a new place to go

my next new gaming system when I upgrade my dual monitor corsair gaming tower that i have had since 2011

You will look like the fat Captain of the Ship in the movie Wall-e! In that scorpion chair gaming…Needs Cheetos cabinet and an energy drink cooler added! (Just for truth to power and full realism).

it would look slick in the corner in my unit to finish up the last 8 years of work from home in

If you were looking at the Dvorak above, and were in the FL panhandle of Pensacola or Tallahassee you may be escaping for higher ground right now. And that could be very misleading IMHO.

Very different presentations from Sat. views and radar views. As far as direction of movement. The radar view shows more, while the satellite views seem to show nothing but Very Soon to be Doom! Pull back the covers, because that towering blanket of convection is massively huge looking.

That is one very ominously amazing sat. view pic of 5 simultaneous P, R, S, T, and V storms in the Atlantic/Gulf Basin. (Even if they were only the active global storms at the moment…), but then realizing they are not the only active storms globally…2020 is very active. Stay safe everyone. Thank you Dr’s!

Thanks Dr. Masters. Dangerous Flood situation not just with surge but with rainfall and slow movement, hoping for the best for all.

that face, reminds me of something in a old renaissance painting, I want to say angelic but doesn’t really apply to hurricanes does it.

That looks like some major drifting to the NNW?! I don’t see much westerly motion on this. Is it just WV going a different direction that the LLC?

I think it’s just expanding. On radar it hardly looks like the center is moving at all.


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