Replies to that tweet seem to be implying that he's focusing too much on the core of the hurricane, instead of considering it's wider implications, and that the area they're in (miami beach) is still facing a significant storm surge?
Irma is almost as big as Texas and predicted to swing north (actually, I think it already has?). So the eye being less than three hundred miles south should not be particularly reassuring.
Miami Beach is on the opposite coast that Irma is hitting. It's not going to be an easy day, but the dude is a lot better off than being on the west coast. Storm surge for him is a lot lower than other places in the state as well.
Cruising in Atlanta, lost power hours ago (lol trees growing around power lines) and based on previous storms I'm unsure if I'll get it back for a few days. I'm near important things like Marta, but also seem to be on a tiny grid. Nothing we can't handle at any rate, and the cats are far calmer than expected.
PiptheFairFrequently not in boats.Registered Userregular
Mine and my parents houses are both ok. Mine is without power som I'm staying with them. The drive from north Georgia was awful
Meanwhile here is a Scout in front of mountains
+15
Options
WeaverWho are you?What do you want?Registered Userregular
Got wildfire smoke back in Seattle.
0
Options
ChimeraMonster girl with a snek tail and five eyesBad puns, that's how eye roll. Registered Userregular
Oh hi! IRMAgherd, it's weather thread! That's like my cue right? So 2017 suddenly decided to wake up. After a crazy slow tornado season that briefly got off to a fast start but then suddenly died, 2017 decided to become the year of the major hurricane and dethrone 2004!
Irma and Harvey were hurricanes number 8 and 7 for me. I almost pulled the trigger on the Keys but was unable to get to Marathon in time since my departure from Texas was delayed so I rode her out in Marcos Island, Florida. On our way we drove opposite to the biggest evacuation in US history. From as far as Mobile we started to see the constant and near bumper to bumper traffic as people fled from the storm. Gas is always an issue in any hurricane I have ever chased. Normally what we do is load a car up with as many gas cans as we can fit and fill them full, but that was not going to be enough for Irma. As we drove to our target we had to stop every time the car got down to 3/4 of a tank and top off knowing that we would find stations running out of gas far sooner than later. Once you cross that point where stations are out of gas you have only what you brought with you to not only ride the storm out, but then also get home.
We got to about Tampa and then found stations were running dry and so we nursed our tank all the way down to Naples and once there we lucked out to find a gas station who's pumps were on. The gas trickled out and it took about 30 minutes but we got our tank topped back off from being down only 3/8ths of a tank. With that settled the next plan was to find a base of operations. While we knew that we were going to ride the worst of the storm out from the car, we did find a hotel that was allowing the media to stay with a waiver. We set up there but knew that in a worst case scenario with the surge that the hotel would possibly be under a couple feet of water. Thankfully our room was on the 2nd floor but we could not be there with the car as that would cause it be lost.
After getting unpacked and a power nap from the long drive straight from Texas we then went out to cover the outer rainbands. Surprisingly the outerbands were filled with discrete cells that had supercellular characteristics. Having just had my first hurricane-born tornado in Harvey I was eager to get another one so we drove out into the everglades and tried hard to get a tornado. The lack of roads and the trees made it hard to see what was under the fast moving storms. Adding to this, we had to contend that the motion and layout of the supercells were "upside down." This was due to the storms rotating around the top of Irma's wind field and so in contrast to your normal east moving tornado producing storm in Kansas, we had to deal with a due west motion and a mesocyclone that was on the east side of the storm. One storm in particular tried very hard and had a well pronounced, long lived funnel but we were unable to see under said funnel due to the trees blocking our view and thus cannot confirm if it was a tornado or not.
We then made our way back to town and filmed some interviews with who was left in town. We came across a few that were looking for gas or waited to long to evacuate, a hurricane party in a sports bar that was staying open that night, and the national guard unit that was setting up to respond to the aftermath. All the while we watched the forecast closely just incase we needed to reposition east to Homestead or north to Tampa. Finally we turned in for the night after finishing up after midnight and confident that we would take a direct hit.
That next morning we awoke to tropical storm conditions and found a tree had already fell in the parking lot and onto the back of my car. Luckily the damage was minor but it did cost us a gas can and the fuel it contained. It was then that the news that Marco Island was experiencing a negative storm surge, which is where the wind forces the water out to sea instead of up on land, made it my way. Irma's wind field was over 400 miles in diameter and thus being so large meant that the constant winds blowing out to see in the lead up to the storm was pushing all the west facing bodies of water dry. Having never gotten to see this in person we quickly went to Marco Island and got there in time to see the water was drawn out until it was nearly a foot deep in places that would normally cover my head. Once there we decided that we would stay for the landfall. We had, up until this point, been debating on whether or not to actually chase the storm on Marco or stay in Naples due to the threat of the surge after the eye passed. Irma had been weakening and looked to be moving a bit east of it's forecast. This made us feel that maybe the surge wouldn't be so bad but we still planned for the worst. The danger with staying on Marco was being trapped with little options to get the car above the storm surge, also the road to Marco is through a mangrove swamp and barely above sea level for miles. Even if we made it off the island we would have to out race the southern eyewall or possibly drown on that road. Thankfully she was also moving very slow and baring getting trapped by trees we theorized that once in the eye we could easily drive north inside of it to safety.
While in the north eyewall we found a few areas on Marco Island that, thanks to wind tunneling between the high rise condos, actually had sustained winds in the cat4 range! While not as strong as Harvey's winds were, I was still unable to stand up and was blown a good 50 yards on my back while trying to document them. The winds pounded the island but thanks to Florida's strict building codes the category 3 winds did little to damage most of the buildings there significantly. The same cannot be said for the trees and many of the oaks and other hardwood trees, even the palms, were shredded and fell. We stayed on the far south side of the island as long as we felt was safe to do so and then as the streets started to flood from the rain we moved north through the eyewall winds towards the causeway.
Irma was really interesting for me because of her slow speed I was able to transect the northern eyewall twice. Marco Island was under a mandatory evacuation order and the fear was that, in a worst case scenario, most of the island would be under a minimum of 3 feet of storm surge after the passage of the eye. Because of this we took a risk and decided that if we chose to take a hit in Marco Island we would have to immediately blast north to Naples and then get away from the coast so that we did not get taken out by the surge. Luck would have it that the roads were just clear enough from trees that once the eye arrive we were able to get north. We knew as a back up we could ride out the weaker southern eyewall on the causeway. While that would leave us stranded and exposed to the winds, the south eyewall (given a north storm motion) is usually weaker and Irma was only a three and weakening, so we were confident that we could ride the winds out on top of the bridge.
The roads thankfully were mostly clear and where they weren't we could get around them on the sidewalks. We took my sedan and made our way into Naples and back through the northern eyewall once more. Once in there we had several close calls with debris including the side of the vehicle taking a hit from a stoplight that blew off its wires. We struggled to find a route that was not too deep with freshwater flooding to get the car through but found a path by the airport and so we cleared the surge zone. Once the eye was back ontop of us we retraced our steps after seeing another chaser locate an open garage and so we made our way to that parking deck as we wanted to document the surge and knew that no matter how high it got we would be safe there.
Luckily for Naples and Marco Island the right turn that Irma took meant that thanks to her not staying just west of town, and her rapid deintensification over land, the surge only made it up a few feet above the highest tide. It also helped that the storm made landfall during a +1 low tide, which added to keeping the surge below the forecast for that part of the peninsula.
This was the first time that with in a week I was riding out two major hurricanes at landfall and while both were horrific and prolific it was interesting just how different the two storms were. I also finally broke my curse this year and finally got a storm that made landfall during the day as a major hurricane. While Harvey was hard on my cameras and killed a couple, Irma was very hard on my car. Sadly she is in need of a new radiator, pulley for the AC belt, and AC belt. The bumper is now held on with tape and zipties, she needs a new tail light, and we lost two tires. Hopefully I can get some of my reimbursements back soon enough to get her back in shape as I may be heading out again very soon with her to the coast.
Anywho, HI! It's been a while and I'm not dead. Also, MARIA IS COMING (maybe to OBX, or maybe not)!
+13
Options
ChimeraMonster girl with a snek tail and five eyesBad puns, that's how eye roll. Registered Userregular
Oh and in Harvey I almost died, filmed a sat truck get it's dish torn off, had the hotel we were in partially collapse, rescue a chaser who got stranded in the surge zone when his car was blown off the highway by the winds, and spent a few days on a boat in Houston helping/filming rescues.
+1
Options
ChimeraMonster girl with a snek tail and five eyesBad puns, that's how eye roll. Registered Userregular
edited September 2017
INSANE FACTS ABOUT IRMA:
Irma expended more accumulated cyclone energy during its life than all the Atlantic hurricane seasons COMBINED since 2009.
Irma was the second strongest storm in wind speed the Atlantic basin has ever seen. (Allen was stronger by 5mph and was in the Gulf).
Irma had the strongest sustained winds ever seen in the open Atlantic Ocean.
Irma is the strongest tropical cyclone ever observed in terms of energy spent in the satellite era.
Irma spent more time as a category 5 storm than any storm on record, including outside the Atlantic basin.
Irma was the first cat 5 to hit Cuba in nearly 100 years (1924 was the last time).
Irma is he strongest storm to ever make landfall at peak intensity in the Atlantic basin.
Peak gusts in the eyewall of Irma were likely up to 225mph.
Hurricane Irma and Harvey mark the first time on record that two storms of cat4 or stronger have ever made landfall on the US in the same season.
Irma tied with the Labor Day Hurricane of 1935 to be the strongest landfalling hurricane ever in the Atlantic basin.
2017 marks the first time that two storms were ongoing in the Atlantic basin at the same time with both having winds =/>150mph (Jose and Irma).
When hitting Florida, Irma's tropical storm winds had a diameter of ~400miles, wide enough to stretch the gap from Tallahassee to Miami, FL.
Irma prompted the largest evacuation and reverse evacuation in United States History.
Irma is currently the deadliest storm of the 2017 season overall and in the US.
Irma's eye was big enough to completely fit the island of Barbuda inside of it.
Irma is tied at 10th place for lowest observed pressure since 1950 in the Atlantic basin with a minimum central pressure of 918mb.
Irma was a Cape Verde-type Hurricane that made landfall multiple times in both annular and classic storm modes.
Irma's winds were so strong/loud they actually registered on the Richter scale due to vibrating the ground and objects they were hitting.
On a sad note, I must note that Irma succeeded destroyed my childhood summer home and resting place of my mother on St. John in the USVI.
Chimera on
0
Options
FishmanPut your goddamned hand in the goddamned Box of Pain.Registered Userregular
Irma was a Cape Verde-type Hurricane that made landfall multiple times in both annular and classic storm modes.
I was mostly with you up to here. What does this mean?
Hurricanes can take on two modes. One is annular and the other is... non-annular. I call that the classic type. Annular storms are typically the most violent. If you were to put two cat 5 hurricanes side by side, say that had the same wind field size and were of the same intensity of sustained wind you would often find the annular storm will do more wind damage in its eyewall. The reason for this I will get into in just a moment.
First let us examine how to identify the two types of hurricanes. Annular hurricanes typically are perfectly symmetrical, or very near so, and have shed most if not all of their pronounced rain bands. They are commonly referred to as truck tires, donuts, or buzzsaws among meteorologists and storm chasers for their distinct satellite appearance. Below is a few examples. Note how they lack any real rain bands, have massive open eyes, and a jagged edge around the cirrus deck.
The last image is Irma, see how she lacks bands and is just a big buzzsaw blade? Now lets look at some non-annular hurricanes.
There you can see the distinct difference between the two. Sometimes though you will have storms that form around the edge of a hurricane that are not actually true rainbands and only loosely associated with the hurricane. Don't let these fool you into thinking a storm is not annular. Take a look at this image here and you will see the pronounced fat circular and symmetrical CDO (central dense overcast) region of the cyclone giving away that it is an annular hurricane.
During a hurricane's lifespan they will often replace their inner eyewall as a means of maintaining themselves. When these eyewall replacement cycles happen a storm will briefly weaken a minuscule amount. While vulnerable at this moment, it does not mean a hurricane is on the way out. In fact it usually means the storm is getting larger in diameter and stronger overall and once finished a storm will often come out with even higher winds and lower pressure as long as it is not disturbed in the process.
Depending on the conditions present, when a storm transitions to annular it will do so during one of these cycles. It starts by forming a second, larger eyewall around the first one. This happens when the rainbands become more circular to the storm and begin to overlap until they form a concentric band that circles the inner eye completely. A gap in between the two will exist and is called "the moat." For a time on radar the core of the storm will take on a bullseye pattern. Normally the outer eyewall will shrink and choke off the inner eyewall, killing it and replacing it. If it shrinks enough the storm will not become annular. In an annular transition the inner eyewall dies but the outer eyewall does not shrink, rather it becomes thicker and the process to create more rainbainds seems to stop in favor of building a thicker eyewall. This process is not well understood but one theory suggests that eddies form along the edge of the eyewall that mix the calmer winds of the eye in with the intense winds of the eyewall. These eddies are known as mesovorticies.
Lets look at the radar of a non-annular hurricane. We will use Charlie as an example since it was a strong category 4 upon landfall in Punta Gorda, FL.
The arrow is pointing to the intense yet tiny eye and eyewall of the storm. Around the eyewall you will see a visible moat (the green circle) and then out from there you will see the rainbands in yellow and orange. Charley still has visible banding on radar, but these were well on their way to starting an eyewall replacement cycle (ERC). This is evident because the bands closer to the center of the storm have begun to overlap into a large shield of orange on radar, and a moat is visible around the eyewall. Despite that it is clear that Charlie is not annular despite how strong it was.
Once annular a hurricane will rarely go through an ERC since it lacks the necessary rainbands to initiate one. They typically only do so once disturbed by land or a change in water temps. Annular storms do not fare well in sheared or dry environments but do last longer over colder waters than a classic hurricane.
Now why is it important to note if a storm is annular or not? Well it is because of those mesovortices that I mentioned earlier. The ones found in an annular hurricane are typically larger and much more violent than those in a normal hurricane. They help maintain and strengthen an eyewall by introducing the warm buoyant air from inside the low level of the eye into the updrafts of the eyewall. In an annular hurricane they can become so violent that they actually behave like, and cause similar damage to a tornado. The best examples of this can be found in hurricane Harvey and Andrew. Both were annular storms at landfall and both had exceptionally violent vorticies in them.
In the image below you can actually see the ones from Harvey that were captured by a DOW (Doppler on wheels) which is a radar truck that is typically used to study tornadoes in the plains. The image is of the reflective (the rain, ice, and particles in the clouds of the storm being reflected back, what you see on TV most of the time) on the left and the velocities (the direction and speed of the wind) on the right.
The way to read them is as follows.
Reflectivity: The hotter the color, the more intense the rain fall is and the stronger the convection (storm) is there.
Velocity: The colder the colors (green to blue to purple to black) the faster the wind is moving to the left of the image. The hotter the colors (yellow to orange to brown to red) the faster the winds are moving to the right of the image.
The DOW is sitting inside the calm eye. The red circles with arrows indicate the mesovorties locations and spin, the yellow line indicates the edge of the eye and the path they are orbiting on.
Those are found on the very edge of the eye, have the strongest wind gusts, and do the most damage. When you hear Irma had winds gusting to 225mph, it is in these that it was happening. Since they are on the very edge of the eyewall it gets immediately calm a lot of the time just after they pass since the eye then moves over top of you. It is interesting to note that, while on visible satellite images an eye may appear to be a perfect round stadium, in actuality they are not as represented by this radar image of Harvey. Had Harvey been allowed to stay over water another hour or so, it would have hit Texas as a Cat 5 and been as strong as Irma was most likely. Harvey was under rapid intensification thanks to these mesovorticites despite being over the continental shelf. It is one of these that cause the hotel I was in to lose a wall and part of its roof.
Here is what these monsters can do:
So why are they so much worse in an annular storm? Well in this case, size DOES mater. Let us examine the size and shape of an eye in both an annular and non-annular storm using two hurricanes we have already shown.
The mesovorticies in a tiny eye just cant grow to the scale or intensity and are not nearly as stable as in an annular storm. Also the hurricane force wind field is often smaller, much smaller, and so you just don't get the same kind of wind damage between the two.
Most hyper violent storms like Irma was are annular, but only a tiny number of tropical cyclones ever make it to this storm mode. When Irma hit Barbuda and the USVI it was annular, when it hit Cuba it was transitioning back to non-annular, and when it hit Florida it was not annular. This shows why we saw different levels of wind damage, even in areas hit by cat4/5 winds.
+13
Options
JedocIn the scupperswith the staggers and jagsRegistered Userregular
You nerd. Don't ever change.
+13
Options
lonelyahavaCall me Ahava ~~She/Her~~Move to New ZealandRegistered Userregular
I'm seriously having a bit of a fangirl moment over here after those posts @Chimera
I'm seriously having a bit of a fangirl moment over here after those posts @Chimera
Stay safe, and stay awesome!
Haha thanks! If you like those, then keep an eye out for my posts in the [science] thread! Right now I am trying to secure a way to economically get to Puerto Rico. There is a good chance that Maria hits as a cat 4 or even a 5 with the way it is rapidly organizing though finding a way there and back that doesn't cost 500-600 is proving hard, and that's before the rental car! I can definitely make the money back but it is having it upfront that is hard. I already spent most of my expense savings on Harvey and Irma. I wish these storms were a little more spaced out.
Posts
Unfortunately it's about Hurricanes For All.
Guy: Actually probably shouldn't be worse than this windy state right now. It's skipped this area, you know.
Reporter: Okay cut the interview. You had one job, guy.
Hous[e is fine too, but that is literally the least of our concerns.
Even so, having a house is a very good thing so that's good to hear!
Most of my city is without
Might take a few days
Meanwhile here is a Scout in front of mountains
Irma and Harvey were hurricanes number 8 and 7 for me. I almost pulled the trigger on the Keys but was unable to get to Marathon in time since my departure from Texas was delayed so I rode her out in Marcos Island, Florida. On our way we drove opposite to the biggest evacuation in US history. From as far as Mobile we started to see the constant and near bumper to bumper traffic as people fled from the storm. Gas is always an issue in any hurricane I have ever chased. Normally what we do is load a car up with as many gas cans as we can fit and fill them full, but that was not going to be enough for Irma. As we drove to our target we had to stop every time the car got down to 3/4 of a tank and top off knowing that we would find stations running out of gas far sooner than later. Once you cross that point where stations are out of gas you have only what you brought with you to not only ride the storm out, but then also get home.
We got to about Tampa and then found stations were running dry and so we nursed our tank all the way down to Naples and once there we lucked out to find a gas station who's pumps were on. The gas trickled out and it took about 30 minutes but we got our tank topped back off from being down only 3/8ths of a tank. With that settled the next plan was to find a base of operations. While we knew that we were going to ride the worst of the storm out from the car, we did find a hotel that was allowing the media to stay with a waiver. We set up there but knew that in a worst case scenario with the surge that the hotel would possibly be under a couple feet of water. Thankfully our room was on the 2nd floor but we could not be there with the car as that would cause it be lost.
After getting unpacked and a power nap from the long drive straight from Texas we then went out to cover the outer rainbands. Surprisingly the outerbands were filled with discrete cells that had supercellular characteristics. Having just had my first hurricane-born tornado in Harvey I was eager to get another one so we drove out into the everglades and tried hard to get a tornado. The lack of roads and the trees made it hard to see what was under the fast moving storms. Adding to this, we had to contend that the motion and layout of the supercells were "upside down." This was due to the storms rotating around the top of Irma's wind field and so in contrast to your normal east moving tornado producing storm in Kansas, we had to deal with a due west motion and a mesocyclone that was on the east side of the storm. One storm in particular tried very hard and had a well pronounced, long lived funnel but we were unable to see under said funnel due to the trees blocking our view and thus cannot confirm if it was a tornado or not.
We then made our way back to town and filmed some interviews with who was left in town. We came across a few that were looking for gas or waited to long to evacuate, a hurricane party in a sports bar that was staying open that night, and the national guard unit that was setting up to respond to the aftermath. All the while we watched the forecast closely just incase we needed to reposition east to Homestead or north to Tampa. Finally we turned in for the night after finishing up after midnight and confident that we would take a direct hit.
That next morning we awoke to tropical storm conditions and found a tree had already fell in the parking lot and onto the back of my car. Luckily the damage was minor but it did cost us a gas can and the fuel it contained. It was then that the news that Marco Island was experiencing a negative storm surge, which is where the wind forces the water out to sea instead of up on land, made it my way. Irma's wind field was over 400 miles in diameter and thus being so large meant that the constant winds blowing out to see in the lead up to the storm was pushing all the west facing bodies of water dry. Having never gotten to see this in person we quickly went to Marco Island and got there in time to see the water was drawn out until it was nearly a foot deep in places that would normally cover my head. Once there we decided that we would stay for the landfall. We had, up until this point, been debating on whether or not to actually chase the storm on Marco or stay in Naples due to the threat of the surge after the eye passed. Irma had been weakening and looked to be moving a bit east of it's forecast. This made us feel that maybe the surge wouldn't be so bad but we still planned for the worst. The danger with staying on Marco was being trapped with little options to get the car above the storm surge, also the road to Marco is through a mangrove swamp and barely above sea level for miles. Even if we made it off the island we would have to out race the southern eyewall or possibly drown on that road. Thankfully she was also moving very slow and baring getting trapped by trees we theorized that once in the eye we could easily drive north inside of it to safety.
While in the north eyewall we found a few areas on Marco Island that, thanks to wind tunneling between the high rise condos, actually had sustained winds in the cat4 range! While not as strong as Harvey's winds were, I was still unable to stand up and was blown a good 50 yards on my back while trying to document them. The winds pounded the island but thanks to Florida's strict building codes the category 3 winds did little to damage most of the buildings there significantly. The same cannot be said for the trees and many of the oaks and other hardwood trees, even the palms, were shredded and fell. We stayed on the far south side of the island as long as we felt was safe to do so and then as the streets started to flood from the rain we moved north through the eyewall winds towards the causeway.
Irma was really interesting for me because of her slow speed I was able to transect the northern eyewall twice. Marco Island was under a mandatory evacuation order and the fear was that, in a worst case scenario, most of the island would be under a minimum of 3 feet of storm surge after the passage of the eye. Because of this we took a risk and decided that if we chose to take a hit in Marco Island we would have to immediately blast north to Naples and then get away from the coast so that we did not get taken out by the surge. Luck would have it that the roads were just clear enough from trees that once the eye arrive we were able to get north. We knew as a back up we could ride out the weaker southern eyewall on the causeway. While that would leave us stranded and exposed to the winds, the south eyewall (given a north storm motion) is usually weaker and Irma was only a three and weakening, so we were confident that we could ride the winds out on top of the bridge.
The roads thankfully were mostly clear and where they weren't we could get around them on the sidewalks. We took my sedan and made our way into Naples and back through the northern eyewall once more. Once in there we had several close calls with debris including the side of the vehicle taking a hit from a stoplight that blew off its wires. We struggled to find a route that was not too deep with freshwater flooding to get the car through but found a path by the airport and so we cleared the surge zone. Once the eye was back ontop of us we retraced our steps after seeing another chaser locate an open garage and so we made our way to that parking deck as we wanted to document the surge and knew that no matter how high it got we would be safe there.
Luckily for Naples and Marco Island the right turn that Irma took meant that thanks to her not staying just west of town, and her rapid deintensification over land, the surge only made it up a few feet above the highest tide. It also helped that the storm made landfall during a +1 low tide, which added to keeping the surge below the forecast for that part of the peninsula.
This was the first time that with in a week I was riding out two major hurricanes at landfall and while both were horrific and prolific it was interesting just how different the two storms were. I also finally broke my curse this year and finally got a storm that made landfall during the day as a major hurricane. While Harvey was hard on my cameras and killed a couple, Irma was very hard on my car. Sadly she is in need of a new radiator, pulley for the AC belt, and AC belt. The bumper is now held on with tape and zipties, she needs a new tail light, and we lost two tires. Hopefully I can get some of my reimbursements back soon enough to get her back in shape as I may be heading out again very soon with her to the coast.
Anywho, HI! It's been a while and I'm not dead. Also, MARIA IS COMING (maybe to OBX, or maybe not)!
On a sad note, I must note that Irma succeeded destroyed my childhood summer home and resting place of my mother on St. John in the USVI.
I was mostly with you up to here. What does this mean?
Hurricanes can take on two modes. One is annular and the other is... non-annular. I call that the classic type. Annular storms are typically the most violent. If you were to put two cat 5 hurricanes side by side, say that had the same wind field size and were of the same intensity of sustained wind you would often find the annular storm will do more wind damage in its eyewall. The reason for this I will get into in just a moment.
First let us examine how to identify the two types of hurricanes. Annular hurricanes typically are perfectly symmetrical, or very near so, and have shed most if not all of their pronounced rain bands. They are commonly referred to as truck tires, donuts, or buzzsaws among meteorologists and storm chasers for their distinct satellite appearance. Below is a few examples. Note how they lack any real rain bands, have massive open eyes, and a jagged edge around the cirrus deck.
The last image is Irma, see how she lacks bands and is just a big buzzsaw blade? Now lets look at some non-annular hurricanes.
There you can see the distinct difference between the two. Sometimes though you will have storms that form around the edge of a hurricane that are not actually true rainbands and only loosely associated with the hurricane. Don't let these fool you into thinking a storm is not annular. Take a look at this image here and you will see the pronounced fat circular and symmetrical CDO (central dense overcast) region of the cyclone giving away that it is an annular hurricane.
During a hurricane's lifespan they will often replace their inner eyewall as a means of maintaining themselves. When these eyewall replacement cycles happen a storm will briefly weaken a minuscule amount. While vulnerable at this moment, it does not mean a hurricane is on the way out. In fact it usually means the storm is getting larger in diameter and stronger overall and once finished a storm will often come out with even higher winds and lower pressure as long as it is not disturbed in the process.
Depending on the conditions present, when a storm transitions to annular it will do so during one of these cycles. It starts by forming a second, larger eyewall around the first one. This happens when the rainbands become more circular to the storm and begin to overlap until they form a concentric band that circles the inner eye completely. A gap in between the two will exist and is called "the moat." For a time on radar the core of the storm will take on a bullseye pattern. Normally the outer eyewall will shrink and choke off the inner eyewall, killing it and replacing it. If it shrinks enough the storm will not become annular. In an annular transition the inner eyewall dies but the outer eyewall does not shrink, rather it becomes thicker and the process to create more rainbainds seems to stop in favor of building a thicker eyewall. This process is not well understood but one theory suggests that eddies form along the edge of the eyewall that mix the calmer winds of the eye in with the intense winds of the eyewall. These eddies are known as mesovorticies.
Lets look at the radar of a non-annular hurricane. We will use Charlie as an example since it was a strong category 4 upon landfall in Punta Gorda, FL.
The arrow is pointing to the intense yet tiny eye and eyewall of the storm. Around the eyewall you will see a visible moat (the green circle) and then out from there you will see the rainbands in yellow and orange. Charley still has visible banding on radar, but these were well on their way to starting an eyewall replacement cycle (ERC). This is evident because the bands closer to the center of the storm have begun to overlap into a large shield of orange on radar, and a moat is visible around the eyewall. Despite that it is clear that Charlie is not annular despite how strong it was.
Once annular a hurricane will rarely go through an ERC since it lacks the necessary rainbands to initiate one. They typically only do so once disturbed by land or a change in water temps. Annular storms do not fare well in sheared or dry environments but do last longer over colder waters than a classic hurricane.
Now why is it important to note if a storm is annular or not? Well it is because of those mesovortices that I mentioned earlier. The ones found in an annular hurricane are typically larger and much more violent than those in a normal hurricane. They help maintain and strengthen an eyewall by introducing the warm buoyant air from inside the low level of the eye into the updrafts of the eyewall. In an annular hurricane they can become so violent that they actually behave like, and cause similar damage to a tornado. The best examples of this can be found in hurricane Harvey and Andrew. Both were annular storms at landfall and both had exceptionally violent vorticies in them.
In the image below you can actually see the ones from Harvey that were captured by a DOW (Doppler on wheels) which is a radar truck that is typically used to study tornadoes in the plains. The image is of the reflective (the rain, ice, and particles in the clouds of the storm being reflected back, what you see on TV most of the time) on the left and the velocities (the direction and speed of the wind) on the right.
The way to read them is as follows.
Reflectivity: The hotter the color, the more intense the rain fall is and the stronger the convection (storm) is there.
Velocity: The colder the colors (green to blue to purple to black) the faster the wind is moving to the left of the image. The hotter the colors (yellow to orange to brown to red) the faster the winds are moving to the right of the image.
The DOW is sitting inside the calm eye. The red circles with arrows indicate the mesovorties locations and spin, the yellow line indicates the edge of the eye and the path they are orbiting on.
Those are found on the very edge of the eye, have the strongest wind gusts, and do the most damage. When you hear Irma had winds gusting to 225mph, it is in these that it was happening. Since they are on the very edge of the eyewall it gets immediately calm a lot of the time just after they pass since the eye then moves over top of you. It is interesting to note that, while on visible satellite images an eye may appear to be a perfect round stadium, in actuality they are not as represented by this radar image of Harvey. Had Harvey been allowed to stay over water another hour or so, it would have hit Texas as a Cat 5 and been as strong as Irma was most likely. Harvey was under rapid intensification thanks to these mesovorticites despite being over the continental shelf. It is one of these that cause the hotel I was in to lose a wall and part of its roof.
Here is what these monsters can do:
So why are they so much worse in an annular storm? Well in this case, size DOES mater. Let us examine the size and shape of an eye in both an annular and non-annular storm using two hurricanes we have already shown.
The mesovorticies in a tiny eye just cant grow to the scale or intensity and are not nearly as stable as in an annular storm. Also the hurricane force wind field is often smaller, much smaller, and so you just don't get the same kind of wind damage between the two.
Most hyper violent storms like Irma was are annular, but only a tiny number of tropical cyclones ever make it to this storm mode. When Irma hit Barbuda and the USVI it was annular, when it hit Cuba it was transitioning back to non-annular, and when it hit Florida it was not annular. This shows why we saw different levels of wind damage, even in areas hit by cat4/5 winds.
Stay safe, and stay awesome!
Democrats Abroad! || Vote From Abroad
Haha thanks! If you like those, then keep an eye out for my posts in the [science] thread! Right now I am trying to secure a way to economically get to Puerto Rico. There is a good chance that Maria hits as a cat 4 or even a 5 with the way it is rapidly organizing though finding a way there and back that doesn't cost 500-600 is proving hard, and that's before the rental car! I can definitely make the money back but it is having it upfront that is hard. I already spent most of my expense savings on Harvey and Irma. I wish these storms were a little more spaced out.