Hurricane Alley

[MiamiensisWx]

Question: In regards to S Fl landfalls as recorded in the research. Wilma strikes the SW Fl coastline (Gulf of Mexico). Of course she moves over the penninsula bringing hurricane force winds along the S Fl Atlantic coastline also. So Wilma then is included in the landfall list for the Atlantic Coast too? Suppose Wilma was counted only for the stretch of coastline which received the original hit. Would the disparity change the numbers in regard to Fl as being the Hurricane Capital of the U.S.?

Hey, Berwick Bay.

I believe that the hurricane landfall project analysis classifies storms as direct strikes on a particular county (or parish) if the area receives hurricane-force winds. This applies to the entire United States coastline (from Maine to Texas). It includes barrier islands and islets, too. In that regard, you are correct that Wilma is counted as a direct hit for both coasts of south Florida. The Keys (offshore Monroe County) are included, too. If I am incorrect, someone can find the actual answer.

I believe that the disparity would not change; the entire track across a region is included within the strike data. It largely depends upon the classification of the region where the landfall point took its place. This is just my opinion.

[Berwick Bay]

Thanks for the info Miami. Seems to me that by counting the same storm for both Gulf and Atlantic Coasts (and maybe you should, I'll save that for right now) the statistics for S Fl landfalls have to be skewed.
For Ex. during the last 40 years or so (encompassing parts of two hurricane cycles--- seventies-early nineties, and now mid nineties to present), how many major hurricane strikes were there on the SE Fl Coast from the Atlantic (not crossover storms from the Gulf). Lets see, ummm, oh yes, there was one(Andrew)!! So if you don't count the crossover storms you only have one major storm to effect this stirp of coast during the better part of one and a half hurricane cycles. Now remember, I'm not saying that you shouldn't count these "crossdressers", but it has to make a huge impact on the statistics. Especially when comparing SE Fl (Miami landfall rates, with a small strip of coastline right in the middle of the Northern Gulf (Miss-Al) or with an equally small strip which juts out into the Atlantic at about 35N (Hatteras-Outerbanks). Man only one direct hit from a major coming out of your ocean (the Atlantic) in over 40 years. Seems like the population would almost have to be complacent (since there main experience of these storms is in connection with "crossovers" which have traversed a hundred miles of land just to get to the SE coast, which takes storm surge pretty much out of your experience (the most important factor in regards to loss of life in a major).

[Blown Away]

Interesting chart on intensity.

http://www.umbc.edu/ges/student_project ... nsity.html

[Berwick Bay]

Blown Away, that IS a VERY INTERESTING chart. It pops up right at you. Right smack dab in the middle of the Northern Gulf Coast.

[MWatkins]

Thanks for the info Miami. Seems to me that by counting the same storm for both Gulf and Atlantic Coasts (and maybe you should, I'll save that for right now) the statistics for S Fl landfalls have to be skewed.
For Ex. during the last 40 years or so (encompassing parts of two hurricane cycles--- seventies-early nineties, and now mid nineties to present), how many major hurricane strikes were there on the SE Fl Coast from the Atlantic (not crossover storms from the Gulf). Lets see, ummm, oh yes, there was one(Andrew)!! So if you don't count the crossover storms you only have one major storm to effect this stirp of coast during the better part of one and a half hurricane cycles. Now remember, I'm not saying that you shouldn't count these "crossdressers", but it has to make a huge impact on the statistics. Especially when comparing SE Fl (Miami landfall rates, with a small strip of coastline right in the middle of the Northern Gulf (Miss-Al) or with an equally small strip which juts out into the Atlantic at about 35N (Hatteras-Outerbanks). Man only one direct hit from a major coming out of your ocean (the Atlantic) in over 40 years. Seems like the population would almost have to be complacent (since there main experience of these storms is in connection with "crossovers" which have traversed a hundred miles of land just to get to the SE coast, which takes storm surge pretty much out of your experience (the most important factor in regards to loss of life in a major).

The stats aren’t skewed when you try to answer the question that matters most is: How often does a particular area receive hurricane force winds…and how often does an area receive intense hurricane force winds?

For example, take hurricane Andrew for example and lets define the southern most 100 miles of coastline as a region on either side of FL as SE and SW Florida respectively.

Andrew would count as 1 hit for each region. So looking at a regional total and comparing that to the LA coastline when Andrew hit there…they would also get a value of 1 for that event.

At a regional level, then, it all evens out and there is no double counting. Totals aren’t aggregated by region when you take the numbers up to a state level. If a hurricane passed through Dade county then struck Pensacola it would be one event. States are too arbitrary to use as an aggregate…length of coastline alone could denormalize the totals. That’s why smaller sub-sections are used to normalize the data and make regions comparable side by side.

So yeah, Southern Florida is especially vulnerable because they can get hit from both sides. And Wilma was the 3rd most costly hurricane in US history because of it’s impact on SE FL even through it came from the west.

MW

[Javlin]

Interesting chart on intensity.

http://www.umbc.edu/ges/student_project ... nsity.html

Chart is interesting you can see the effect of the Loop current and Gulf Stream(?) effects on the systems.

[Recurve]

Recurve,

I'll offer a friendly clarification with respect to Betsy's intensity. I just wanted to correct some information. According to this official list, Betsy is clearly listed as a Category 3 at its south Florida landfall. The large RMW, pressure gradient, and 954 mbar pressure would suggest a storm within this intensity. Most sources (from my experience) estimate Betsy's top sustained winds in Florida at 105 to 115KT (120 to 132 mph). This is the equivalent of a Category 3 hurricane. In most of the higher estimates, the 115KT has been rounded to 130 mph (borderline threshold between Category 3 and 4). I believe that Betsy featured a large windfield, so it is no great surprise that Miami-Dade County received some significant effects from this storm.

Thanks for the correction that officially Betsy was a 3 at Keys landfall. I forgot that, I'd been referring to old advisories and went with the "120-140 mph" estimate just before landfall from Miami Weather Bureau, thinking that made it a Cat 4 at that time. Haven't heard of any reliable wind records from on Key Largo itself. Such a large windfield would indicate relatively lesser winds as you point out. Unlike those tight little monsters Andrew and Labor Day. It does seem the houses in my neighborhood survived with some flood damage; this area might have been in the eye for as long as three hours, while areas farther north were in the eyewall longer.

[Ivanhater]

Thanks for the info Miami. Seems to me that by counting the same storm for both Gulf and Atlantic Coasts (and maybe you should, I'll save that for right now) the statistics for S Fl landfalls have to be skewed.
For Ex. during the last 40 years or so (encompassing parts of two hurricane cycles--- seventies-early nineties, and now mid nineties to present), how many major hurricane strikes were there on the SE Fl Coast from the Atlantic (not crossover storms from the Gulf). Lets see, ummm, oh yes, there was one(Andrew)!! So if you don't count the crossover storms you only have one major storm to effect this stirp of coast during the better part of one and a half hurricane cycles. Now remember, I'm not saying that you shouldn't count these "crossdressers", but it has to make a huge impact on the statistics. Especially when comparing SE Fl (Miami landfall rates, with a small strip of coastline right in the middle of the Northern Gulf (Miss-Al) or with an equally small strip which juts out into the Atlantic at about 35N (Hatteras-Outerbanks). Man only one direct hit from a major coming out of your ocean (the Atlantic) in over 40 years. Seems like the population would almost have to be complacent (since there main experience of these storms is in connection with "crossovers" which have traversed a hundred miles of land just to get to the SE coast, which takes storm surge pretty much out of your experience (the most important factor in regards to loss of life in a major).

The stats aren’t skewed when you try to answer the question that matters most is: How often does a particular area receive hurricane force winds…and how often does an area receive intense hurricane force winds?

For example, take hurricane Andrew for example and lets define the southern most 100 miles of coastline as a region on either side of FL as SE and SW Florida respectively.

Andrew would count as 1 hit for each region. So looking at a regional total and comparing that to the LA coastline when Andrew hit there…they would also get a value of 1 for that event.

At a regional level, then, it all evens out and there is no double counting. Totals aren’t aggregated by region when you take the numbers up to a state level. If a hurricane passed through Dade county then struck Pensacola it would be one event. States are too arbitrary to use as an aggregate…length of coastline alone could denormalize the totals. That’s why smaller sub-sections are used to normalize the data and make regions comparable side by side.

So yeah, Southern Florida is especially vulnerable because they can get hit from both sides. And Wilma was the 3rd most costly hurricane in US history because of it’s impact on SE FL even through it came from the west.

MW

Wow, I didnt know if a hurricane hit south florida then hit Pensacola that was counted at 1 event....so when Erin hit east Florida then came back over the gulf and hit Pensacola, just because it hit the same state, was 1 event....that is interesting

[Berwick Bay]

Categories, categories, categories. And this refers to me too. It was a 3, no it was a rapidly increasing strong 2. Or this. Well after reviewing the evidence, we upgrade from 4 to 5. Well flight level winds as opposed to ground level winds, you see the ratio has changed. This was based on one last observation just hours before landfall. But what about surge at that part of the coast and pressure, don't they still support a 4? Well they do, but we made the change anyway.

Question: Scientific foundation for demarcation of categories established in the Saffir-Simpson Scale. As winds increase, damage inflicted on structures increases geometrically not just arithmetically. So isn't a 90-95 mph storm many times stronger than a 74-80 mph storm?? But same category. 74-95 mph storms all lumped together. The scale is pretty wide. Shoudn't the category levels get smaller or encompass a smaller range of wind speeds as the storm gets more powerful? Ex. Should the CAT 4 Category be so wide as to include storms of 131-135 along with 151-155? Shouldn't the 155 mph storm be many, many times more powerful than the 131-135? Shouldn't that difference be much greater than storms at the high and low end of the Cat 1 classification?

I guess I'm grumpy today. This whole classification thing bugs me. I think I need to write a poem. Comes closer to the truth. Waiting for arrival of Chantal. And very beautiful she is, leaving childhood, and coming into the full bloom of womanhood, as June is the embodiment of youth and confidence in reference to the coming hurricane season. Chantal is flirtatious, yet innocent. Not yet fully aware of her effect upon the world of men. I sense her arrival, she will be here shortly. She will blush, because without really understanding why, all eyes will be upon her. She will be the center of attention and talk of the gala. That is how it must be.

[bubbamills]

Berwick, I agree with you on this category classification :D Too many people get too caught-up in this and some suffer from it rather harshly.

[Recurve]

Just to throw another thought into the mix, something from the NHC:

Miami has the highest frequency of hurricane force winds in the U.S. Detailed climatological data can be found at the Miami National Weather Service Forecast Office.

(At least, that's what they tell visitors here: http://www.nhc.noaa.gov/aboutvisitor.shtml)

As for the SSHS categories being pretty wide, there's the H*Wind project and the new kinetic energy/damage potential scale that Powell et al have worked up. A brief story I wrote on it is here http://www.upperkeysreporter.com/articles/2007/05/18/news/news10.txt
The HRD intro page is here: http://www.aoml.noaa.gov/hrd/data_sub/wind.html

[Berwick Bay]

Nice report, Recurve. So this new scale will be availabe to the public this year?? If so, will the NHC provide the infor, of will it be provided at the discretion of you local weather office?

[Recurve]

Nice report, Recurve. So this new scale will be availabe to the public this year?? If so, will the NHC provide the infor, of will it be provided at the discretion of you local weather office?

Powell told me that reports using the scale would be posted directly on the Web, so would be available to the public. He said they would be ready once the season officially started (they didn't do it for the first storm, and I don't know if anything was posted for Barry.) That kind of suprised me. He made sure to explain that it would NOT be updated around the clock, and it will NOT be a forecast -- they would give a rating of a storm at a fixed point in time, from actual, not projected, data.

I'm sorry to say I don't have the exact URL of where their reports will be posted. Powell is with HRD, so I'm assuming somewhere in there. I'll check and post anything I find. If anyone else knows, please post.

-DH

[cpdaman]

guys i think the data for the south central fl thru keys region in florida verifies that it is a PART OF HURRICANE ALLY

and i think the data for the 120 mile stretch of coast from ext. E LA thru 120 miles east including s. miss and alabama also OBVIOUSLY verifies it is PART OF HURRICANE ALLY

does anyone have a problem with this?


and i am not just trying to make both sides compromise, the data is pretty clear that there are two distinct areas (one covering a larger area than the other) where hurricane strikes are markedly higher. thus HURRICANE ALLY'S may be a more appropriate term

and the people from florida surprised by the frequency of storms in part of the gulf coast region just got a weather lesson. guys be thankful

p.s i am from palm beach, FL

[Recurve]

No doubt, cpdaman. Amen, too.

[rjgator]

Categories, categories, categories. And this refers to me too. It was a 3, no it was a rapidly increasing strong 2. Or this. Well after reviewing the evidence, we upgrade from 4 to 5. Well flight level winds as opposed to ground level winds, you see the ratio has changed. This was based on one last observation just hours before landfall. But what about surge at that part of the coast and pressure, don't they still support a 4? Well they do, but we made the change anyway.

Question: Scientific foundation for demarcation of categories established in the Saffir-Simpson Scale. As winds increase, damage inflicted on structures increases geometrically not just arithmetically. So isn't a 90-95 mph storm many times stronger than a 74-80 mph storm?? But same category. 74-95 mph storms all lumped together. The scale is pretty wide. Shoudn't the category levels get smaller or encompass a smaller range of wind speeds as the storm gets more powerful? Ex. Should the CAT 4 Category be so wide as to include storms of 131-135 along with 151-155? Shouldn't the 155 mph storm be many, many times more powerful than the 131-135? Shouldn't that difference be much greater than storms at the high and low end of the Cat 1 classification?

I guess I'm grumpy today. This whole classification thing bugs me. I think I need to write a poem. Comes closer to the truth. Waiting for arrival of Chantal. And very beautiful she is, leaving childhood, and coming into the full bloom of womanhood, as June is the embodiment of youth and confidence in reference to the coming hurricane season. Chantal is flirtatious, yet innocent. Not yet fully aware of her effect upon the world of men. I sense her arrival, she will be here shortly. She will blush, because without really understanding why, all eyes will be upon her. She will be the center of attention and talk of the gala. That is how it must be.

There has to be some type of intensity scale and I agree with you about the pressures created by the wind. There are also several other factors that come into play besides the exponential increase in PSF (Pounds per SF) of pressure that is created on a structure that people and especially older structures were not designed for. The PSF force that is placed on a structure increases with the height of the structure to the leverage that is created when the same force is applied over a taller structure. I.e. if the wind is blowing at 100MPH the effective pressure used in structural design in the first 15' is 32.6 PSF. Due to the leverage the same 100 MPH wind on a 60' tall structure is 43.9 PSF. There are also different levels of exposures depending on what part of the structure the wind is blowing on. I.e. design pressures in the corners of structures are much higher than the center.

IMO people become far too complacent with the potential impacts of storms due to the categories. They may have experienced the weak side of a category 1 storm and only barely seen 75MPH wind gusts and think that a category two storm should be not to much worse when they might be on the strong side and getting sustained winds of 110 MPH. This would exert approx. 246% more pressure on the typical 1 story structure. That would be like having a typical 3'X5' window = 15SF with 240lbs of sand getting dumped and then removed and dumped and removed over and over at 75 MPH or almost 600LBS at 110 MPH and 826lbs at 130 MPH. Data from Premier industries Technical Center Design Pressures

The other thing I have been wondering about is the recent influx of people buying impact rated windows. They are a great product however my concern is what happens in multiple impacts? Upon impact the windows do shatter and the film in between each layer of glass keeps the glad from essentially falling out of the frame. However, after multiple impacts the film and glass will continue to stretch and deteriorate and the deflection of the glass will increase with multiple impacts and positive and negative pressures created by the storm will eventually lead to the glass being pulled out of the frame itself. This is only my opinion but look at it this way. Once an impact window is broken by a flying concrete block even if it is still holding in place would you still want to stand behind it? To be approved as impact resistant the windows are shot with an 8' long 2X4 balistically and they must now allow it to penetrate. However they do not shoot it 10 times as may occur in a real storm. Shutters however are rigid and IMO when used with the properly designed windows have a better chance of surviving multiple impacts. The bigger issue I see with the amount of impact glass that is being installed in new houses in South Florida and around the country there is already limited supply of the glass. If there is a significant event there will be a lot of windows that get damaged and it will take an enormous amount of time to get them all fixed. Shuttered houses will simply have to take the shutters off and if all else was OK will not have anything else to worry about except maybe a few dented shutters. This also would have a huge impact on the insurance payouts in a hurricane prone area as the impact windows would be enormous expense to have replaced. This is my opinion but should be weighed if anyone is in the process of getting shutters or new impact windows. Of course impact windows are more convenient and we can all hope that this type of event does not happen.

This is all in my opinion and any research on design pressures, window protection standards, and or hurricane protection should be conducted by a licensed professional.