Chicago Severe Weather Updates: September 2017

Tuesday, September 19, 2017

hurricane updates

Two updates and one recap on what is shaping up to be the worst hurricane season since 2005.

Jose

Jose is still churning in the Atlantic 12 days after its formation. The good news is that despite some coastal erosion and flooding it is not likely to make a direct landfall in the U.S.

Maria

Maria is a horrific Category 5 hurricane with current sustained winds of 160 mph. It made a direct hit last night on Dominica, and the early reports of damage are as bad as you would expect. Due to their small size and location it is actually rare for islands in that vicinity to suffer direct hits from major hurricanes. Records are spotty before ~1970 but this is believed to be the first-ever Category 5 to hit Dominica. Much like Irma for St. Martin and Barbuda and others, this storm will have life-altering consequences for many thousands of people.

Maria is also unique because it went from a newly formed hurricane to a Category 5 monster in just over 24 hours. That kind of intensification is insane. It weakened due to its brief encounter with Dominica but it has already regained Category 5 strength over open water. And now Maria is taking aim at Puerto Rico. The odds are very high that Puerto Rico will take a direct hit or glancing blow from a major hurricane. Again, this is not as common as it might seem – Georges in 1998 was the last major (Category 3 or higher) hurricane landfall. This storm is likely to be Category 4 or 5, with devastating winds and 1-2 feet of rain that will cause horrendous flooding and mudslides. The exact path is uncertain, of course, but a direct hit could lead to the worst-ever hurricane impact on Puerto Rico. Anyone in the path – which also includes the U.S. Virgin Islands – should pay close attention and heed evacuation orders.

The only good news is that Maria is likely to head north and stay east of the U.S. mainland.

Cat. 5 formation map – via @philklotzbach

Irma recap (note: I wrote this last week but forgot to send it, so it may need to be update for the latest information and developments)

Back to good news / bad news. The good news is that many people took heed of the forecasts and got out of harm’s way. A storm of this strength could have killed far more people than it did. (The death toll in Florida as of this writing is 42 and still climbing.) The other good news is that even though the impacts ranged from catastrophic in the keys to severe in the Naples area, this could have been far worse. The storm not only weakened a little bit right before landfall, it also jogged inland by about 30-40 miles. That minor difference spared all three major metros (the Naples, Miami and Tampa areas) from a direct hit. Improved building codes also lead to much more manageable property damage in most areas. Still, the loss of life and property is tragic. This storm will go down among the costliest in American history. Other facts and figures:

A comprehensive list of Irma data and records established: https://webcms.colostate.edu/tropical/media/sites/111/2017/09/Hurricane-Irma-Records.pdf
Irma made landfall in the Keys at 929 mb, tying for seventh place among all landfalling U.S. hurricanes.
- Except for the unfortunate Keys, the track could not have been better – the core of the eyewall went through the Everglades, just east of the SW Florida cites and just west of Miami. A major bullet was dodged through the luck of that 30-40 mile variation.
Recorded wind speeds (note – several sites in the Keys failed early, and other reports are still being compiled):
- 142 mph Naples
- 130 mph Marco Island
- 99 mph Miami Int’l
Official rainfall totals in the 6-15 inch range. Highest total at Ft. Pierce/St. Lucie County Airport (15.91”).
With almost 20 million people affected, and with a massive evacuation and disruption to work/school, this may have been one of the most disruptive storms in American history
All major Florida airports remain closed for at least the second consecutive day, disrupting schedules nationwide. Miami Int’l Airport took significant water damage and will be closed for at least one day longer than expected.
6 million customers (58% of the entire state) were without power on Monday morning as of 6 am EDT.
After pulling toward the west for days, a last minute jog back to the east saved many areas – especially the entire Tampa area – from far worse flooding.
- The prior jog to the south was Cuba’s great misfortune, but the Category 5 landfall there was enough to weaken the storm considerably before it turned north.
- Key West – the most populated area of the Keys – also got a major break when it caught the less-dangerous part of the storm as the front-right quadrant over the storm passed 30-40 miles to the east over less developed areas.
A cluster of thousands of birds got trapped inside the eye of the storm, and it was big enough to be visible on radar.
Most of the paint on the ocean-facing side of the “Southernmost” buoy on Key West was scoured off by the waves and wind.
On the opposite corner of the state from the original landfall, Jacksonville set the all-time record for flooding at its downtown site (St. John’s River at Main Street bridge), breaking a record set by Hurricane Dora in 1954. Savannah, GA and Charleston, SC are also seeing major flooding. Additional inland flooding from rainfall is ongoing.
By one measure (“Accumulated Cyclonic Energy”) Irma by itself generated the Atlantic basin’s full-season average of storm energy
The surge in Naples was higher during Donna, reportedly – it predates official records there – but Irma set the record since then
One storm chaser got a handheld wind measurement of 117 mph in the Keys: https://t.co/VhC97GZJBa
A vivid example of storm surge in the Keys: https://twitter.com/CNN/status/907025993914658817
A construction crane in Miami was snapped – thankfully the 20-25 others in the city did not come down. (picture below)
Brickell Ave. in Miami suffered extensive flooding. (pictures below)
A word on forecasting. In short, this was a qualified victory. The margin of error for forecasting has dropped by about 50% in the last 15-20 years, and this is a good example of that. It would be wonderful to be able to pinpoint the details of the center of circulation and intensity, but that’s just not possible at this point. The complexity of the atmosphere requires an immense of calculating power to provide any reasonable approximation, and it does not allow more accurate forecasts than what you see below.
- Every official NHC forecast fell within the cone. More than four days of advance warning was provided with accuracy <100 miles. (Again, the landfall occurred 90 miles from downtown Miami, and that landfall was well within the projection. NHC provided more than 45 official forecasts dating back to August 30^th when it was a tropical wave off the coast of Africa. Yes, the forecasts need to get better, but that is always true.

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Saturday, September 9, 2017

RE: last Irma update

Some minor changes with significant impacts, so one more update: The entire Florida peninsula is still going to see hurricane conditions and the news could hardly be worse for the Keys and the SW coast from Naples to Tampa.

The steering winds have caused one of the possible 25-50 mile shifts in the track, resulting in less-bad news for Miami and awful news for the Keys and SW/W Florida. Miami/Homestead is still going to see Category 1-2 conditions and a few feet of storm surge. There will be surge problems from Miami to Charleston but the track has shifted to the far western side of the possible ranges mentioned yesterday. That alleviates some of the problems on the east side of Florida while making things far worse for the west coast. (And don’t pay attention to the “cone” – that is the range of uncertainty about the exact center of the storm. There will be hurricane conditions well outside the stupid cone graphic.)

Irma made landfall in Cuba last night with Category 5 winds. The interaction with land weakened the storm somewhat, but as it reemerges over very warm waters it is likely to strengthen again. Category 4 winds (130-140 mph sustained and 150-160 mph gusts) are likely over the Keys and into Marco Island-Sanibel-Naples-Fort Myers. If the eye stays just offshore it could retain 130-140 mph winds for almost the entire length of the state. Storm surge of 5-10 feet is going to be a huge problem as well. A catastrophic surge of 15 feet is possible in some places. NHC says specifically that “Storm surge flooding of 10-15 ft is now expected along the SW Florida coast. This is a dire and life-threatening situation.” An 8-foot surge in Tampa and 10-12 feet in Naples is as serious as it gets – anyone in an evacuation zone should absolutely evacuate. Most of Lee County looks vulnerable a massive surge. Tampa is also one of the country’s most prone major cities to a major hurricane and surge, and every tick to the west puts it in greater danger. There is now a plausible scenario with a Category 4 hurricane paralleling the coast and making a direct hit on Tampa.

The Keys will see the first landfall in the early hours of Sunday morning. Key West or somewhere within 20-30 miles will likely take a direct hit. And there is going to be a 40-50 mile swath of extreme devastation. The director of the National Hurricane Center says that he does not know if the conditions will be survivable for anyone who remains on the Keys. That is not exaggeration – the average elevation on many of the islands is 5-7 feet, and the surge could easily reach 8-10 feet with catastrophic wind damage. The mandatory evacuation order is not to be ignored.

From: Philip C. Ordway [mailto:pordway=anabaticllc.com@mail183.sea22.mcdlv.net] On Behalf Of Philip C. Ordway
Sent: Friday, September 8, 2017 3:49 PM
To: Philip C. Ordway <pordway@anabaticllc.com>
Subject: last Irma update

Well, the bad news keeps coming. Florida is looking at a major hurricane and possibly a historically devastating one – the chances of a total miss are almost gone, and severe, if not catastrophic, damage in the state is all but assured. It is tempting to feel numb to the massive amount exposure this storm has had all week, but the forecasts have verified and now it’s here.

Irma weakened through its “eyewall replacement cycle” and as it began to interact with some wind shear. Now, to make matters worse, it has begun to intensify again as it hits some of the warmest ocean water in the world. Winds are back to 155 mph sustained and – even though it doesn’t make any material difference – it could regain Category 5 status at any point tonight or tomorrow. (The official and arbitrary cutoff is 157 mph.) At landfall, sustained winds will likely be 140 mph or higher, and that is catastrophic for any locations in the direct path.

The landfall location down to the last 50-75 miles is still up for debate. That will be crucial in determining localized damage that will range from severe to extreme but there are no “good” options. The details are less important if you consider that a ~75-mile-wide swath (almost the entire width of south Florida) will see Category 4 devastation and literally everyone in Florida from Orlando south will see Category 1-3 conditions and damage. A huge storm surge threat is emerging from Jacksonville to Charleston on the right side and from Tampa to Naples on the left side – this storm is that massive and that powerful.

The ECMWF model won again. The trend, which ECMWF correctly picked up again, has been to the west. Each run is nudging the track a few miles west. If that pans out it is a marginal improvement for Miami – although far from a salvation – and a massive problem for the Naples-Fort Myers area.

The current best guess is an early Sunday landfall over the central Keys (near or west of Islamorada, with an elevation of ~7 feet and a storm surge that could top 10 feet) and the far SW tip of Florida. That would spare Miami the absolute worst of the storm, but it would bring awful conditions to SW Florida and over a larger area as it crawls almost directly up the spine of the peninsula. A 25-50 mile shift west would be worse for the west coast of Florida, and a 25-50 miles shift west would be worse for Miami all the way up to Charleston, SC. If the current guess prevails, that would take 140-160 mph gusts over the Keys (with catastrophic damage) and 110-140 mph gusts into Marco Island-Naples-Fort Myers. To the extent that Miami prepared and SW Florida did not, that is a massive problem. Even in this scenario Miami would see winds 90-110 mph with a storm surge of 5-9 feet along the coast leading to significant wind damage and severe flooding. All of south Florida will see a foot or more of rain.

But the main message is that the luck ran out. Regardless of the specifics, severe wind damage and a major storm surge is on the way. The peak surge in SW Florida calls for 6-12 feet from Captiva to Cape Sable, and 5-10 feet from Jupiter Inlet to the Keys as well as in Biscayne Bay and Miami Beach. That is a big, big problem.

Media preview

This is going to be a top-five hurricane by strength at landfall for Florida. It will probably be a top-five hurricane by total dollars of damage. Only a handful of hurricanes have ever hit the U.S. with higher sustained winds, and even fewer have presented as much storm-surge potential. The only comparable storms in modern Florida history are Andrew (1992) and Charley (2004). Irma will have winds ~20-30 below Andrew’s and at least as strong as Charley’s but likely with worse storm surge damage than either.

There is going to be flood/surge damage from the west coast of Florida all the way to Charleston, SC. Any areas that saw flooding during Matthew will likely seeing flooding that is equal to or worse than that. The hurricane-force windfield (with ~100 mph gusts) will likely be wider than the entire Florida peninsula. 60-80 mph gusts – and power outages – could make it all the way to Atlanta by Monday.

The situation is already grim. People seem to be heeding the warnings, which is great, but reports show gas stations in the Miami area were already empty on Thursday night. Grocery stores have been cleaned out. Traffic is a nightmare. Hopefully the next 24 hours will give enough time for people to secure property and get away from the ocean.

On a more trivial level, the economic impact will be significant. Travel delays will last for days if not weeks. MIA, FLL, and MCO, among others, will be closed for a few days, disrupting flight schedules across the country. Tens of billions of dollars will be lost and countless homes will be ruined. Somewhere around two million homes could lose power, and in some places it may not come back for days. Florida Power & Light is already making plans to shut down its nukes, and these kinds of winds can snap even the sturdiest wood/metal power poles.

Media preview

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Friday, September 8, 2017

last Irma update

Thursday, September 7, 2017

update on Hurricane Irma

Here is an update on Hurricane Irma – there is good news and there is bad news, but it is mostly bad news. This is a very serious storm and it’s going to take a lot of luck to avoid a major disaster in Florida. The odds now favor this storm joining Andrew, Camille, Katrina, Harvey and others among the most infamous hurricanes in American history. There is still time for luck to come out on our side, but there is precious little time left to prepare for a potential catastrophe.

Irma has weakened slightly, as expected, but the bad news is that it weakened from a near-record 185 mph sustained to a still-obscene 175 mph. (Pressure rose from 914 mb to 923 too.) Depending on the track we could drop all the way to 130-140 mph. That would be better than the alternative, but at that level we would still have a major catastrophe. The track will come into better focus (within a margin of error of 50 miles or so) by tomorrow night. The intensity is always tougher to pinpoint, but the overwhelming odds favor a major (Category 3 or higher, with sustained winds of 111-129 mph) making landfall on Saturday/Sunday. I think a Category 4 (130-156 mph) is more likely than Category 3.

The range of potential tracks is narrowing but still fairly wide, and there is room for Irma to miss Florida just off the coast (much as Matthew did last year). But this storm is huge, and there will be a path ~100 miles wide that experiences flooding and wind damage. A difference of just 20-30 miles could be the decider between devastation and moderate damage. There is still quite a bit of disagreement among the models down to the last 50-100 miles on Sunday morning, and that makes all the difference for the big population centers.

Here is a great time lapse of the official NHC cone/track projections. Notice the wobbles, which are important, but also notice how they track is broadly accurate over time. https://video.twimg.com/tweet_video/DJI-MJNV4AA0h4G.mp4

The bad news is that most tracks are zeroing in on south Florida, with Miami-Dade right in the bull’s-eye for some models. One experimental model puts a catastrophic Cat. 5 (906mb) landfall at Key Largo. (That would be the worst-case scenario, with the strongest winds and highest storm surge going right into Biscayne Bay and Homestead-Miami. I’d take the under on that wind/pressure, but as noted above it only helps so much.) One good model (ECMWF) just took the track back to the west by a few dozen miles, making landfall farther west in the Keys and SE of Marco Island before raking the entire Florida peninsula from north to south. That model puts hurricane-force winds through the entire state east of Tallahassee, and while it would be awful for the areas that suffer a direct hit it would be better for the major population centers.

Adjustments will have to be monitored right through the weekend. For now, the best-case of a total miss is <10% likely by my subjective compilation of the actual quantitative estimates. That leaves a 90% chance of a major hurricane landfall or near-landfall with hurricane-level damage in Florida. Events with a one-in-10 probability happen all the time, of course, but this is still very serious given the outcomes in the other nine cases.

I’d also put the odds at >50% for a direct hit in south Florida by a Category 3+ hurricane with severe damage and life-threatening conditions. I would split the difference in the direct-hit scenario, with about even odds between 90-120 mph winds in Miami and 140-150+ mph winds in Miami.

Again, the margin of error still exists, and there are no certainties. The extreme winds and surge could stay just offshore. But that is not the way to bet right now. Evacuation orders are up and they should be obeyed -- this is no time to play Russian roulette. And traffic already looks like a nightmare, so waiting until the last minute could be a problem.

A particular concern with Irma is the storm surge. Just as Harvey was a catastrophic wind producer over a small area but an even worse threat over a wide area from rainfall/flooding, Irma may do the same with its storm surge. See below for some NOAA simulations on storm surge from a Category 3 landfall at high tide.

The other bad news is that there is a growing likelihood that Irma will continue up the Florida peninsula – with significant damage all along the path – and possibly make a (second) landfall on the GA/SC/NC coast. One plausible – not assured, but plausible – scenario takes a strong hurricane into the Savannah/Hilton Head area. Another plausible scenario to the west takes 70-90 mph gusts all the way into Atlanta. But again, that is about four days away and important adjustments will have to be made. Other possible scenarios include a slow-wind down of the storm as it grinds north without a second landfall, in which case the damage in Georgia and South Carolina would be significant but more moderate. The bottom line is that everyone in the state of Florida east or south of Tallahassee and everyone on the east coast south of North Carolina should be paying attention to this storm.

Root for the American model. Unfortunately, the European model has been more accurate in recent years.

Other random notes:

There has not been a Category 5 landfall in the U.S. since Andrew in 1992. (Hopefully Irma will be *only a Category 3 or Category 4 at landfall. But Katrina was a 3, Harvey was a 4, etc.)
- Irma is roughly twice as big as Andrew. (The size and intensity at landfall are what matter, of course, and we’ll see. But Irma has already achieved higher winds than Andrew ever did, and its current hurricane-force windfield is ~100 miles across verus. 50-60 miles for Andrew. See below for images in a similar position that are roughly to scale).
Coastal flooding is going to be a major problem. Low-lying areas and/or anything within close proximity of the beach is going to be major flooding. The storm surge forecast is 5-10 feet from Palm Beach to Miami to the Keys to Naples, and that is not likely to be wrong on the high side.
Construction cranes in Miami pose a special threat because they are engineered to withstand 145 mph winds. Gusts could easily exceed that in the direct-hit scenario and there is no way to secure them in advance.

Irma had a measured sustained wind of 185 mph for 37 hours straight – that is the all-time record for the planet in the satellite era (back to 1967, with caveats). It is normally not possible for anything but a Super Typhoon in the west Pacific to sustain 175+ for more than a 6-12 hour period.
Irma is tied for second place in the Atlantic with 185 mph sustained winds. Only Allen in 1990 had officially sustained winds of 190 mph.
The landfall Irma just made in the leeward islands is tied for second place all-time on the planet for sustained winds at 185 mph. Only three Super Typhoons in the Philippines and Taiwan were stronger at 190 mph (a rounding/measurement error, really). In this hemisphere no storm has ever hit land with stronger sustained winds; the Great Labor Day Hurricane that hit Florida in 1935 is officially credited with 185 mph sustained winds, but that is obviously speculative at best. The next closest would be a trio of storms at 175 mph, including Camille in 1969.
The devastation in the Caribbean is extreme and the pictures are stunning. Loss rates – the number insurers use to calculate the share of buildings that will require substantial or total repair – are in the 30-90% range across several islands. The human tragedy is just beginning to come into focus.
Wind speeds were apparently strong enough on Barbuda to snap cell towers made of reinforced steel.
Hurricane Jose is roaming the Atlantic behind Irma, and it could impact some of the islands recently hit by Irma. For now the long-range track for Jose looks to be out into the open Atlantic. The tracks and atmospheric dynamics of both Jose and Katia could also play a role in Irma’s ultimate track.
By coincidence, exactly seven years ago there were three hurricanes (Igor, Julia, and Karl) in almost the exact same locations as Irma, Jose, and Katia today.

Here is one simulated IR satellite snapshot for Saturday morning. If that is even close to accurate – it’s far from infallible but it’s very likely close to accurate – it should send a chill down the spine of everyone in Florida.

NWS Miami is not messing around – nor should they.

Andrew:

Irma:

Tuesday, September 5, 2017

Irma update

Sorry for one more email, but this is an unreal situation with wide-ranging impacts. I will save future updates for Thursday/Friday when the track will come into better focus, but all travel plans – let alone anyone with friends or property in the path of the storm – should be on notice.

Irma has continued to intensify through the day, with the latest pass measuring sustained winds of 185 mph. This is now at the very high end of any storm ever measured on the planet, and vying for the all-time record in the Atlantic basin. It is a picture-perfect example of a powerhouse hurricane, and there is nothing to stop it in the immediate future. Some models are testing their theoretical limits and suggesting winds of 200+ mph soon. Even if that doesn’t happen – and even if, as is likely, there is some weakening on Thursday/Friday – this is a dangerous monster of a storm.

The islands in the direct path (Barbuda, St. Barts, Sint Maarten, Anguilla, Tortola, St. John, others) and west toward much of the Caribbean face total devastation in any areas that suffer a direct hit tonight or tomorrow. Puerto Rico, Hispanola and Cuba are also in danger. Even without a direct hit the damage could be severe.

On the U.S. mainland the trends are not looking good. We’re still right on the edge of effective models, and there is a high degree of dispersion among the possible tracks. There is a weak and growing consensus that south Florida could (repeat: could) take a direct hit from a Category 4 or Category 5 hurricane on Saturday/Sunday. There is some chance of a brush with Cuba which would weaken the storm, but not enough to make it “safe.” There is some chance of a recurve to the north before it reaches Florida, but that is probably a <10% chance right now. There is some chance that the core of the storm slides south, into the Gulf of Mexico, but that would still bring a massive surge and damage to south Florida and the Keys, to say nothing of the impact in the Gulf itself. And the most likely outcome right now is a landfall somewhere in south Florida that rivals some combination of Wilma and Andrew.

A mandatory evacuation of the Florida Keys begins tomorrow. All of south Florida may see similar evacuation orders for coastal areas within a day or two. The NFL has already cancelled the Dolphins game in Miami on Sunday. Airports in Florida (MIA, FLL, RSW) will see significant cancellations and likely multi-day closures. And of course this says nothing about the potential human tragedy or broader economic disaster.

Hurricane Irma

After Hurricane Harvey made landfall as a very rare Category 4 and proceeded to nearly stall over SE Texas with catastrophic flooding consequences (total damage, much of it uninsured, could be in the $70-90 billion range), we have a new problem.

Hurricane Irma came off the west coast of Africa with the classic look of a “Cape Verde” hurricane. (Many of the hemisphere’s strongest hurricanes have formed near the Cape Verde islands in the far eastern Atlantic.) True to form, this morning Irma was upgraded to a Category 5. It is the strongest Atlantic hurricane in a decade and it is already in rare territory for any hurricane, having hit 175 mph sustained winds (see below). That puts it on par with the max intensity of such disasters as Katrina, Andrew, and Camille, among others. It is also the furthest east (57.5 degrees west) of any 175-mph storm on record. That gives it an unprecedented length of wide-open warm water. Conditions are perfect for a monster hurricane to persist – or even to strengthen – over the next few days.

And the projected track could not be worse. Our best hope right now is either a glancing blow off the mountains of Cuba (which would be terrible for Cuba but might be just enough to disrupt the circulation as it approaches Florida) or a dramatic and unexpected recurve out to sea. The latest projections have been tipping westward, into Cuba, but at this point there are no good options. The next 2-3 days will see an untouched Category 4/5 hurricane roll across the Atlantic, and by Thursday we’ll have a better idea of the track. The intensity is tougher to pinpoint -- Harvey just exploded into a Category 4 from a standing start in the Gulf over a mere two days -- so that issue will remain fuzzier than the track. At some point the hurricane will “cycle” and it could well be downgrade to Category 3 or 4. But that may not matter much, and it is normal for a storm like this to evolve through time. In any case, the odds are very favorable for a major (Category 3 or higher) landfall in the Caribbean and/or Florida by Friday into the weekend. A track and potential redevelopment in the Gulf is also looking likelier by the day. Anyone within 500 miles of this storm should be paying close attention.

Here are three possible tracks – these are model simulations only and far from assured. They are illustrative only because they are reasonable and, if verified, would be an enormous problem for South Florida and the Miami area.