October 19, 2018

Texas' Lake Travis Approaches Record Levels as Heavy Rain Continues

It's been pretty calm across most of the United States for the past week, a far cry from what we've experienced for...well, the entire year up until now. Hurricane Michael is out of the picture, the raging Santa Ana winds in southern California have calmed down, and the rest of us only see the occasional passing shower, if that. The only active weather in the United States right now is a persistent slog of heavy rain over Texas, and the persistent slog of rain for days on end is leading to some pretty big flooding problems.

Parts of Texas have recorded more than a foot of rain over the past week. The heaviest rains have fallen in the central part of the state. Much of that rain fell in a short period of time, and much of it fell across the Colorado River watershed.

The surge of water into the Colorado River led to a significant rise in Lake Travis, northwest of Austin that's created by the Mansfield Dam. Water levels in the lake have exceeded major flood stage, and the pool is just six feet shy of its record high of 710 feet. The excess water in Lake Travis is flooding surrounding communities. Water levels are so high that officials may have to open all eight flood gates on the dam, something they've never had to do before.

The National Weather Service has flood characterizations for every major waterway in the country, detailing the kind of flooding you can expect once water levels reach a certain point. Here are the characterizations for flooding on Lake Travis:

714 Flow reaches and goes uncontrolled over the emergency spillway over Mansfield Dam at Lake Travis. Hundreds of homes around Lake Travis flood, many with water well over their roofs or in the second floor level.
710 Hundreds of homes around Lake Travis at Graveyard Point at Lakeway flood with water well over some roofs and into the second floor of lower homes.
705 Disastrous residential flooding of hundreds of homes occurs around Lake Travis at Graveyard Point at Lakeway, many with water over their roofs in up to 17 feet of water.
700 Many homes flood at Graveyard Point at Lakeway on Lake Travis, some with water to their roofs in up to twelve feet of water.
695 Lowest temporary and mobile homes in Graveyard Point at Lakeway on Lake Travis have up to seven feet of water in them.
691 The lowest permanent homes at Graveyard Point at Lakeway on Lake Travis flood. Several temporary homes are in several feet of water.
688 Lowest temporary and mobile homes at Graveyard Point at Lakeway on Lake Travis flood.
685 The lowest temporary and mobile homes at Lakeway at Graveyard Point on Lake Travis are threatened.

The lake is just a few inches shy of the level at which "disastrous residential flooding" is possible, and any further rise in water levels will have a significant impact on surrounding communities.

The region isn't hurting for rain anymore. Drought conditions that existed across large parts of Texas for the past year vanished with the onset of heavy rains over the past month. Only small pockets of drought conditions remain over parts of Texas that largely avoided the recent rains.

Heavy rain will continue across parts of the southern Plains through Saturday, and the greatest chances for heavy rain over the next week will be confined to southern Texas and the Gulf Coast.


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October 12, 2018

A Look at Tropical Storm Michael's Unexpectedly Intense Winds in Central N.C.

More than a million people in North Carolina and Virginia are without power this evening as energy crews try to repair the damage caused by Tropical Storm Michael's passage on Thursday. The Piedmont region was particularly hard hit, unexpectedly experiencing high-end tropical storm conditions for more than an hour during the height of the storm. I live in Rockingham County, North Carolina, one of the hardest-hit areas and a county that saw nearly 70% of its residents lose power during the worst of the storm.

Nasty conditions were in the forecast for central North Carolina for days before the storm. The main risk was always going to be flooding from heavy rain, which we saw in abundance. Tropical storm warnings were in effect for many inland locations to reflect the risk for high winds during the storm, but the warnings were mostly confined eastern parts of the state in the lead-up to the storm on Thursday and only expanded westward on Thursday morning.



The storm here in Rockingham County was relatively tame for most of the day. It poured all day. The winds picked up a bit in the early afternoon hours as the center of Tropical Storm Michael drew closer to the area. I even tweeted a video of the heavy rain and breezy conditions to make note of how well the winds were behaving despite the heavy rain and our proximity to the center of the storm.

That didn't last long.


I was in the living room around 3:00 PM when I heard a loud thunk on the roof. I turned around to look out the window and saw a cloud of leaves and debris swirling over our apartment building. I got away from the window in time to see the trees twisting and bending like I'd never seen during any of the awful storms we've had in the past. The sound of the wind was horrendous, made even worse by the howling whistle coming through the cracks in the windows and front door.

The wind grew stronger as the minutes wore on, at first in buffeting gusts but eventually settling into a steady, constant roar. Shingles and window shutters peeled off of our apartment buildings. The blizzard of leaves and branches and occasional roofing debris and building material whizzed by the window and over the roof. The power flickered on and off for a while before finally giving out about 30 minutes into the ordeal. The wind finally started to calm down after almost an hour.

I had to go back and piece together a timeline to make sure my perception of time wasn't biased by my anxiety. It really did last about an hour. The strongest winds began right around 3:00 PM. I first tweeted about the kicking winds at 3:02 PM. The National Weather Service issued a severe thunderstorm warning about ten minutes after the damaging winds started, alerting Rockingham and Caswell Counties, as well as several counties in Virginia, of the potential for damaging winds of up to 70 MPH. The Storm Prediction Center received a report of a possible tornado in Reidsville at 3:20 PM. A tornado warning was issued at 3:42 PM for more areas of rotation spotted on radar. I noted that the wind had finally died down around 4:00 PM.

Nearly 70% of Rockingham County's 50,000 electric customers lost power at the height of the storm, and more than half still had no power by midnight the following day. The entire City of Danville, Virginia, lost power for the night after the storm. Many counties in central parts of North Carolina and Virginia saw more than half of their residents lose power as a result of the intense winds on Thursday afternoon, according to PowerOutage.US.

I don't like to see the word "unexpected" in weather reporting. Many weather events really aren't unexpected. The folks in harm's way who didn't expect a natural disaster likely weren't listening to forecasts and warnings ahead of the storm. However, I feel comfortable using "unexpectedly" in the headline of this post because the extent of the damaging wind event we experienced was not well-forecast nor was it well-warned in the areas struck by the destructive winds today.

Forecasts regularly mentioned the potential for wind gusts as high as 40 or 50 MPH as the storm passed to our southeast, but what we experienced went well beyond that—for all intents and purposes, parts of the Piedmont in North Carolina and Virginia experienced the winds of a high-end tropical storm for an hour. On top of that, the hardest-hit counties were never placed under a tropical storm warning, and the severe thunderstorm warning for 70 MPH winds wasn't issued until about 10 minutes after the damaging winds started howling.


The National Hurricane Center found Tropical Storm Michael's maximum sustained winds around 50 MPH as the center of the storm passed through North Carolina on Thursday afternoon. The agency analyzed the extent of its tropical storm force winds reaching to the southeast of the center toward the coast.

If that wasn't the bulk of the storm, then what was it?

The windstorm we experienced in north-central North Carolina was more akin to a persistent severe thunderstorm than a full-fledged tropical storm. The winds in a tropical cyclone are driven by the storm's intense pressure gradient. Air rushes in to fill the void left by the low pressure in the middle of the storm, creating the destructive winds in a storm.
Source: Tropical Tidbits

The winds in a tropical cyclone are much stronger just above the surface than they are at the surface. Winds grow stronger with height because they're not limited by the effects of friction. The winds at the 850 millibar level—a few thousand feet above the surface—were blowing as strong as 70 to 80 MPH as Michael moved across North Carolina.

What appears to have happened is that a line of very heavy showers—essentially, thunderstorms without thunder—formed on the northwest side of Tropical Storm Michael's center of circulation as it passed between Greensboro and Raleigh on Thursday afternoon. This enhanced convection was able to mix-down those powerful winds from just a few thousand feet above the surface. The persistent nature of the thunderstorms caused a prolonged period of high-end tropical storm force winds across parts of the Piedmont in North Carolina and Virginia.

The National Weather Service will conduct a survey in Reidsville on Friday to determine if any of the damage was caused by a tornado. I wondered during the storm whether or not we'd been hit by a tornado right when the winds start, but I'd be surprised if the survey crew found that the damage was caused by anything more than straight-line winds. Most of the damage to our apartment complex was superficial—shingles and shutters torn and tossed, torn vinyl siding, tree damage—but there are lots of reports of more serious damage elsewhere around town and around the county.

The seriousness of the destruction along the Gulf Coast dwarfs what we experienced here in central North Carolina, but such intense winds for such a long period of time is a heck of a thing to experience when you're not expecting it.

(Top Image: CIRA/RAMMB)


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October 10, 2018

Here's Why It's So Hard to Verify a Monstrous Hurricane's Maximum Winds

Hurricane Michael made landfall today near Panama City, Florida, with maximum sustained winds of 155 MPH. Its winds were just a few ticks short of a top-of-the-scale category five, but that doesn't matter to the folks in the path of the storm. This hurricane is an unprecedented disaster, and the pain and suffering for residents in the affected areas is only just beginning. The pictures and videos we saw of the damage from extreme winds and storm surge will only get worse as folks in the hardest-hit areas start to check in with the outside world.

As we see with every storm, the folks who come out of the woodwork on social media after every natural disaster are starting to bray their disapproval with the process that goes into recording the strength of the storm. They like to claim that the maximum winds in the storm were really weaker than advertised and its "official" maximum winds were hyped up for ratings, politics, face-saving, or whatever affirms their conspiracy du jour. We're already seeing that trash talk start before the storm surge has even receded on the Florida coast. I normally wouldn't indulge the nonsense so soon after the disaster, but their concern trolling raises a legitimate question:

Why is it so hard to verify the maximum winds of a hurricane?
Source: Tropical Tidbits
Meteorologists have an enormous array of tools available to them to help survey the world around us. You can use advanced satellites, high-resolution Doppler weather radar, a relatively dense network of observing stations on the ground, and even data collected by airplanes, ships, buoys, and oil rigs to collect information about the strength of a hurricane.

The experts at the National Hurricane Center use all of those methods to determine the intensity of a tropical cyclone leading up to and at the point of landfall. These intensity values are reevaluated at the end of the season to check for accuracy and correct for any mistakes. The above graphic shows data plotted from a reconnaissance aircraft as Michael made landfall on Wednesday afternoon.

While we have all those tools available for analysis, it's hard to directly measure the strongest winds experienced at ground level.

Let's start small by thinking about tornadoes for a second. We can get a decent profile of a tornado based on damage surveys conducted by meteorologists in the days after a storm. Experts surveying the path of a tornado can use damage to structures, vehicles, vegetation, and even the ground itself to estimate the winds in a tornado. We know the EF-5 tornado that tore through Joplin, Missouri, had winds stronger than 200 MPH because, not only did it simply wipe away entire neighborhoods, but it did unfathomable damage like compromising the structure of a five-story hospital and tearing away concrete parking blocks that were staked to the ground with two reinforced steel rods.

We know a whole lot about tornadoes despite the fact that few of them ever directly hit a weather station. The odds of any one tornado directly hitting a weather station are astronomical due to their relatively tiny size. Even in Oklahoma, which is the most tornado-prone region in the world, only four weather stations out of more than a hundred have been struck by tornadoes in the past decade.

Since hurricanes are many hundreds of times larger than tornadoes, any given landfalling storm will hit dozens of weather stations along its path. That gives us a lot of information about a storm as it comes inland, but it doesn't mean that the strongest winds in a storm will hit an unlucky anemometer.

The strongest winds in a hurricane are confined to the eyewall, or the thunderstorms that wrap around the center of circulation. Even though Hurricane Michael had maximum sustained winds of 155 MPH, it doesn't mean that all of the winds in the eyewall were 155 MPH. The peak winds occur in only a very small area of the eyewall, an area that usually only covers a couple of miles of real estate. This maximum is typically located on the right side of the eyewall relative to the forward motion of the hurricane. If the hurricane is moving north, the strongest winds will occur in the eastern eyewall because the winds are flowing in the same direction as the hurricane's forward motion.

It's hard to receive direct ground confirmation of the maximum winds in a hurricane because the maximum winds only encompass a tiny portion of the overall storm, and you would have to get incredibly lucky for that small area to pass directly over a weather station with an anemometer that survives the flying debris and the sheer stress of the wind. Not even during 1992's Hurricane Andrew did a weather station directly sample the storm's maximum winds, despite the category five hurricane's eyewall striking a heavily-populated part of southern Florida, including the National Hurricane Center's own office.


We've seen lots of pictures and videos of horrible damage around Panama City and Panama City Beach this evening. Tyndall Air Force Base, which fell under the northern part of the eyewall and saw sunlight as the eye passed overhead, measured a wind gust of 129 MPH during the worst of the storm. Florida State University's campus in Panama City saw a 116 MPH gust during the passage of the eyewall.

Panama City and Panama City Beach were on the western eyewall. Tyndall Air Force Base was on the northern eyewall. There's so much wind damage in those areas that it looks like a bomb went off.

Here's a look at the damage in Panama City:



Veteran hurricane chaser Josh Morgerman tweeted this evening that he was "literally shocked" at the scope of the damage around Panama City.

But Panama City didn't even see the worst of Hurricane Michael's winds.

However, Mexico Beach did:

 
Pictures and videos from the hardest-hit areas are hard to come by because the power is out and cell phone towers have spotty (or no) service. It'll take a couple of days to get a full idea of the damage inflicted by the hurricane's eastern eyewall.

There were no readily-available weather stations in the eastern eyewall of Hurricane Michael to accurately measure the storm's strongest winds. At least, none that we know of. There could be storm chasers' anemometers or personal weather stations that were located smack in the eastern eyewall that we'll get data from in the coming days and weeks. Meteorologists will be able to use wind damage and storm surge measurements to estimate how strong the winds were as the storm came ashore.

This was an unprecedented hurricane for this part of the country. The Florida Panhandle simply hasn't seen a hurricane this strong since accurate recordkeeping began in 1851. It's going to take a while to account for all the damage. It's likely that people died in the wind and storm surge. It will take years for the area to recover from the storm.

But to say that it wasn't as strong as meteorologists advertised—that they purposely overinflated the numbers—based on a handful of wind reports from the northern and western eyewall is just bunk. It doesn't take direct, observed confirmation of wind speeds to know that this storm was everything they advertised and more.


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Hurricane Michael Nearing Landfall With 150 MPH Winds


Hurricane Michael is just hours from landfall near Panama City, Florida, with maximum sustained winds of 150 MPH. The storm's minimum pressure is now among the top-five lowest for any storm at landfall in the U.S. on record. Its winds are now on-par with those of Hurricane Charley as it made landfall south of Tampa in 2004. No storm this strong has ever struck the Florida Panhandle since reliable records began in the 1800s. We're in uncharted territory now.

My update from last night still mostly holds true. The wind damage and storm surge will be even worse now. It will take longer for the storm to shed its strength as it pushes inland, expanding the area that will see tornado-like wind damage from the core of this hurricane.

Power outages will certainly last weeks—likely months—in the hardest-hit areas. Even inland areas will see weeks-long power outages. Those who stayed (either by choice or circumstance) will face prolonged suffering due to the damage; the lack of electricity and running water, no ability to pump fuel, and shuttered restaurants and stores will leave people in the affected areas completely reliant on their own supplies or those handed out by crews and organizations after the storm.

You still have some hours left if you're in parts of Georgia, South Carolina, and North Carolina, and need to prepare for power outages or flooding. The storm will move at a decent clip once it's inland, but it'll be a sharp sting when it hits.


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Hurricane Michael's Winds Are Forecast to Reach Category Four Intensity by Landfall

Hurricane Michael is an extremely dangerous storm in the eastern Gulf of Mexico this evening. The National Hurricane Center now expects its maximum winds to reach category four intensity by landfall on Wednesday afternoon. The storm will be one of the strongest ever recorded at landfall on the Florida Panhandle, and one of the strongest landfalls we've ever seen so late in the year. Michael poses an extreme risk to anyone who chose (or had no choice but) to stay ahead of the storm's expected landfall near Panama City on Wednesday.

The Forecast



Hurricane Hunter aircraft flying through Hurricane Michael on Tuesday night found that the storm's winds had rapidly intensified to category four status. The storm has maximum sustained winds of 130 MPH with higher gusts. The storm's pressure fell to 943 millibars, down from 970 millibars this time last night.

The forecast at 11:00 PM EDT Tuesday shows Michael making landfall around Panama City, Florida, on Wednesday afternoon, with category four winds. The storm will steadily weaken once it's inland, but it won't wind down immediately. Hurricane force winds are still likely in the eyewall as the center of the storm moves into southwestern Georgia.

This hurricane is the real deal. It will take a major disruption in the internal organization of the hurricane (an eyewall replacement cycle or a sudden intrusion of dry air) to significantly weaken it before landfall. While it's possible, do not count on that to happen.

The hurricane (and, by then, tropical storm) will accelerate as it pushes into the southeast, producing heavy rain and gusty winds. The chance for flash flooding and power outages from wind damage will increase from southwest to northeast as the core of the storm moves through Georgia and into the Carolinas.

Once the storm leaves the North Carolina coast on Thursday night, it will speed out to sea as it loses its tropical characteristics. The storm will bring heavy rain, gusty winds, and rough surf to parts of the Mid-Atlantic coast through the first half of Friday as it exits stage-right.

Here's what we need to watch as Michael makes landfall.

WIND



The storm is forecast to make landfall with 130 MPH winds. This will cause tornado-like damage to a wide swath of Florida's Panhandle and southwestern Georgia along the path of the hurricane's eyewall. The parts of Florida and Georgia in the path of the storm's eye are heavily forested. This hurricane will result in a significant tree blowdown, blocking roads, damaging homes, and severing power lines that could result in widespread power outages that last many days or weeks after the storm.

Hurricane Michael has a very large wind field. Tropical storm force winds (39-73 MPH) extend 300 miles across the width of the storm. Hurricane force winds extend 45 miles away from the eye. Many homes and businesses will sustain some level of wind damage, even those that are far away from the path of the eye of the storm.

The above map shows the NHC's forecast wind radii for each timestep in its 11:00 PM Tuesday forecast. You can mentally fill-in the gaps between timesteps to get a rough idea of the expected swath of hurricane force (dark red) and tropical storm force (orange) winds as Michael moves through the southeast.

For some reference on the kind of wind damage this region can see, Hermine made landfall near Tallahassee in 2016 as a minimal hurricane. Though its maximum winds at landfall were "only" 80 MPH, the storm caused considerable tree and power line damage as it pushed inland. Some residents near Tallahassee were without power for more than a week after the storm.

STORM SURGE


The shape of the coast and marshy terrain of Florida's Big Bend—the concave coast between Apalachicola and Cedar Key that bends northward—makes this part of the coast exceptionally vulnerable to a storm surge. A reasonable worst-case scenario based on the National Hurricane Center's latest forecast would push a storm surge of up to 12 feet above ground level into the Big Bend. This part of the coast is not heavily populated, but thousands of people do live in these areas, so this is a life-threatening situation.

Elsewhere along the coast, especially along and to the east of Michael's eye, a life-threatening storm surge of up to nine feet is possible. This kind of surge can easily inundate homes and businesses near the coast. The prospect of category four winds and a storm surge deep enough to submerge the first floor of homes and businesses puts those who didn't evacuate in a precarious position.

RAINFALL

Hurricane Michael will continue moving at a decent clip once it makes landfall. This will not be a repeat of Florence or Harvey, but any flash flooding is a serious threat to life and property. A swath of rainfall possibly exceeding six inches is possible along the path of the storm from landfall on Wednesday through its exit off the North Carolina coast on Thursday evening.

The greatest rainfall totals are expected along the path of the core of the storm, but training bands of showers and thunderstorms could easily drop higher totals than those shown above. The ground is still saturated in areas that saw heavy rain from Hurricane Florence last month. It would only take a couple of inches of heavy rain in a couple of hours to trigger flash flooding in parts of the Carolinas.

TORNADOES



As we see with any landfalling tropical cyclone, there's a risk for tornadoes on the eastern side of the storm. The forward motion of the storm combined with wind shear can allow thunderstorms in the outer bands to produce tornadoes. The tornadoes that form in tropical cyclones happen quickly and don't give people in harm's way much time to react to tornado warnings.

Why It's So Strong



Michael took advantage of very warm waters, relatively low wind shear, and ample tropical moisture to attain its current strength. The Gulf of Mexico really hasn't seen many storms this year, and that's helped this storm tap into a deep reserve of warm water and explode to its current intensity. The only two storms to enter the Gulf this year were Alberto in May and Gordon at the beginning of September. The lack of storms churning the waters, as well as persistently hot weather right up through this week, has allowed the Gulf to grow warm enough to sustain a storm as strong as Michael.

Historical Context

Past hurricanes with winds of category three or stronger that made landfall within 100 nautical miles of Hurricane Michael's forecast landfall point. | Source: NOAA


Storms this strong don't typically make landfall so far east along the Florida Panhandle. The most recent storms of this intensity to cause serious issues in the Panhandle were Hurricane Dennis in 2005 and Hurricane Ivan in 2004. Hurricane Dennis made landfall near Pensacola, while Hurricane Ivan came ashore in Alabama. The intense winds and storm surge of both storms laid waste to the western Florida Panhandle.

The last time a major hurricane made landfall within 100 nautical miles of Panama City, Hurricane Michael's forecast landfall point, was in 1894. In fact, all three major hurricanes that hit this part of the Florida Panhandle occurred in the 1800s. No hurricane with winds of category four intensity or stronger has ever made landfall along the Florida Panhandle since reliable records began in the 1800s. This storm, if it maintains its intensity through landfall, will be unlike anyone alive has ever experienced along this part of the coast.

Please take this storm seriously, even if you're hundreds of miles inland.


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October 9, 2018

Hurricane Warnings Ahead of Hurricane Michael Stretch Far Inland From the Coast

It can be deceptive to look at a hurricane forecast map if you live inland. The way watches and warnings are drawn for areas in the path of a landfalling storm can be deceptive. The National Hurricane Center's official products only show warnings as thick, colorful lines drawn onto the coast. This can lead to the perception that people who are dozens of miles away from the coast are safe. That's a worrying mistake to make. Hurricane watches and warnings can extend far inland from the coast, and that's very much the case for Hurricane Michael as it approaches the northern Gulf Coast this week.

Hurricane Michael is growing more organized as it moves through the open waters of the eastern Gulf of Mexico. The storm had 110 MPH winds at of 2:00 PM EDT Tuesday, and it's starting to look more like a formidable hurricane with each passing hour.

The latest National Hurricane Center forecast shows Michael's winds reaching category three intensity by landfall on Wednesday. Forecasters expect the hurricane to make landfall on the Florida Panhandle somewhere around Panama City, but everyone from Pensacola to Tallahassee is within the cone of uncertainty, or the margin of error in a hurricane's track based on previous years' forecast errors.

A hurricane doesn't (well, most hurricanes don't) fall apart as soon as their eye crosses the coast. The destructive winds and heavy rain can keep roaring inland, even days after a storm makes landfall. One of the biggest mistakes we can make is expecting a hurricane's ill effects to only unfold right at the coast. As we've seen from recent storms like Harvey and Florence, flooding rains can stretch far inland and lead to disaster. But a storm's strong winds can also follow a storm's path as it treks across land.

Here's what a typical array of hurricane watches and warnings look like based on mapping data provided by the National Hurricane Center. This is how you see watches and warnings depicted on the NHC's official maps, as well as most maps displayed on websites and television broadcasts:

The coastal highlights give you a good idea of which areas are under a warning, but they're deceiving for inland areas.

Here's what the watch/warning map would really look if you included all the counties under alerts:

Big difference!

More than a hundred counties from Mississippi to South Carolina are under some form of watch or warning ahead of Hurricane Michael. Hurricane warnings and tropical storm warnings extend into southwestern Georgia and southeastern Alabama, including the cities of Tallahassee, Dothan, Albany, and Valdosta. Tropical storm watches stretch as far as central South Carolina.

I understand that it's challenging to make a simple map that's also able to cram that much information into one area. The NHC's official map would be an absolute mess if it included all the counties under watches and warnings. That's one of the reasons I make my own maps for my articles. Tinkering with the data usually allows me to display more information than most other outlets, such as cities and highways and inland watches and warnings.

The simple act of issuing a hurricane warning for counties dozens of miles from the coast isn't something to take for granted. Not that long ago, some National Weather Service offices would simply issue a "wind advisory" or "high wind warning" for inland areas along the path of a landfalling tropical system. Getting rid of that kind of inconsistent messaging is one of the small changes the NWS has made in their effort to simplify the warning process and make things easier for people in harm's way to make quick and effective decisions.

(I updated this post at 2:30 PM EDT on October 9, 2018, to reflect the latest information about the hurricane.)


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October 8, 2018

Michael on Track to Hit the Northern Gulf Coast as a Hurricane on Wednesday

Tropical Storm Michael will likely become a hurricane in the Gulf of Mexico on Monday as it gradually accelerates toward the northern Gulf Coast. The storm will likely make landfall on Wednesday somewhere on the Florida Panhandle. Michael will move through quickly, but its strong winds and heavy rain could cause problems from the point of landfall in Florida northward through the Carolinas, still reeling from Florence.

The National Hurricane Center found Michael strengthening quickly on Sunday. It got its act together in a hurry, going from a disheveled tropical depression on Sunday morning to a 60 MPH tropical storm by nightfall. Michael is in a favorable environment for strengthening, and the current NHC forecast shows it doing just that between now and landfall on Wednesday evening. The storm's maximum winds could approach major hurricane strength as it nears land.

Michael could make landfall anywhere between Pensacola and Florida's Big Bend. The most likely area is in the central Florida Panhandle around Tallahassee, but the the precise forecast track will change as the experts get better data and the storm roots itself more firmly in the environment.

Tropical Storm Michael is pinned between a sharp trough over the Southwest and a strong ridge over the Mid-Atlantic. The trough/ridge combo will force Michael to take a relatively narrow path toward and over land. The storm will accelerate as the trough closes in from the west. A fast-moving storm is preferable to a slow-moving storm, since it prevents heavy rain or prolonged winds from causing more issues than they could otherwise. Even so, we're not 

Wind damage and power outages are likely around the point of landfall and for dozens—possibly hundreds—of miles inland. The current NHC forecast shows Michael still packing sustained winds of 65 MPH when it reaches eastern North Carolina on Thursday. While the storm is likely to weaken once it's over land, the potential exists for widespread wind damage along the path of the storm as it moves through the southeast.

A storm surge of several feet above ground level is likely where Michael makes landfall, especially to the east of the eye. The NHC will release more precise storm surge forecasts once watches and warnings are issued on Monday. Florida's Big Bend is exceptionally prone to storm surge. Even a weak storm hitting this part of the coast can cause significant inundation in some coastal areas. Thankfully, much of the area prone to the worst surge is unpopulated, but there are many populated areas and vacation destinations that could be affected by storm surge flooding.


The storm's swift forward motion should preclude an extreme rainfall event along its path, but the Weather Prediction Center still expects at least a couple of inches of rain along Michael's path through the southeast. Some areas could see higher totals where bands of showers and thunderstorms repeatedly move over the same spots. The ground is still water-logged in parts of the Carolinas that saw as much as three feet of rain from Hurricane Florence last month. It won't take much to trigger flash flooding in these areas.

Tornadoes are possible along the eastern part of the storm. The most likely areas to see tornadoes on Wednesday and Thursday are the eastern parts of Florida, Georgia, South Carolina, and North Carolina. Tornadoes associated with tropical cyclones can occur quickly, reducing tornado warning lead time. While these tornadoes are usually small and relatively weak, even the weakest tornado can cause life-threatening damage to buildings and vehicles.

A hurricane watch is likely for much of the Florida Panhandle on Monday. This storm is moving quickly and you don't have as much time to prepare as North Carolina did for Florence. Make sure you have the supplies to make it through a power outage and your property is properly secured from blowing debris or fallen trees.


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October 2, 2018

Four Scientists in Path of Cat 5 Hurricane Walaka As It Approaches Johnston Atoll


The U.S. Fish and Wildlife Services said on Monday that four scientists are in the path of a category five hurricane threatening Johnston Atoll, an isolated atoll in the central Pacific Ocean. Walaka is one of the strongest storms we've seen in the Northern Hemisphere this summer, and its strongest winds may come within a few dozen miles of the tiny island on Tuesday.

The latest advisory from the Central Pacific Hurricane Center pegged Hurricane Walaka's maximum sustained winds at 160 MPH, making it a category five on the Saffir-Simpson Hurricane Wind Scale. Walaka is the second such storm in the central Pacific basin this year; Hurricane Lane reached the top of the scale before approaching Hawaii in August.

Current forecasts bring Walaka's eye within a few dozen miles of Johnston Atoll on Tuesday afternoon. If the predictions hold true, the atoll would fall on the eastern edge of the eyewall, potentially subjecting it to some of the storm's strongest winds and highest storm surge. Rough waves and storm surge could easily cover much of Johnston Island, most of which lies within a few feet of sea level.

Johnston Atoll is located in the central Pacific Ocean about 800 miles southwest of Honolulu, Hawaii. Johnston Island, the atoll's largest feature, is mostly man-made, measuring about two miles long and about half a mile wide. The island consists almost entirely of a runway and various (largely abandoned) government installations.

Johnston Island played a role in the development of the United States' nuclear arsenal. Numerous nuclear tests were conducted there during the height of the Cold War, and Johnston Atoll was heavily contaminated by radiation after the failure of Bluegill Prime on July 25, 1962. The island's population peaked around the turn of the millennium during the effort to rid the island of pollution from both radiation and Agent Orange, large containers of which were stored there after the Vietnam War.

While Johnston Atoll lacks a permanent human population, the U.S. Fish and Wildlife Service told me late Monday night that there are four members of the U.S. Fish and Wildlife Service's biology field crew currently working on the island. A spokesperson for the agency added in an email:


In preparation for any possible impacts from Hurricane Walaka, the field biology crew secured the year-round field camp. We are working with the U.S. Coast Guard to evacuate the four field crew members on Johnston Island, if weather and circumstances allow. Currently, on island staff are sheltering in place at a steel and concrete structure built to withstand hurricanes.

We are continuing to monitor Hurricane Walaka as it moves through the Pacific and will stay in close coordination with the U.S. Coast Guard as the situation evolves.

The spokesperson added that herbicides, insecticides, and propane tanks were secured before the staff took shelter.


The structure referenced by the agency, pictured in the red box in the Google Earth snapshot above, lies on the northeastern side of the island. Walaka (and its strongest winds/surge) are approaching the island from the south. This may somewhat blunt the effect of storm surge flooding if the crew can't evacuate.

A hurricane watch is in effect for the Papahanaumokuakea Marine National Monument, the long chain of tiny islands and atolls that extend for a thousand miles northwest of the main Hawaiian Islands. The center of the storm is not likely to affect any of the northwestern Hawaiian Islands with the capability of supporting a research population.

The storm will not affect the seven populated islands of Hawaii, though rough surf and rip currents are possible along south-facing shores as the storm passes far to the state's west.


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