Major Hurricane Irma

[HKY_WX]

Outflow is very proportional and uninhibited. That means dry air and/or shear is minimal to non-existent w/in the core of the Hurricane. The eye has also been unusually stable over the past 2 or 3 days. Very little change on satellite. To me this looks like routine fluctuations in the strength of a Cat 5 storm. Those qualities are more reminiscent of a Super Typhoon than a Hurricane. I see no reason for it not to maintain and then strengthen as it nears the western Bahamas.

If you look below at the 200mb wind streamlines on the 18z GFS, notice the anticyclonic winds in all channels currently (7pm Today is the first image). This only increases as it nears the western Bahamas on the North side as you can see at 1pm on Saturday. Notices the expansion to the north side thanks to the trough. I expect we'll see a large expansion of feathery cirrus to the north of the storm on Saturday afternoon stretching across the southeast and western atlantic.

 

 

[Stebo]

1 minute ago, tacoman25 said:

Ok, so you think a larger area with lesser damage is worse than a smaller area of more intense damage?

I realize these things can be complicated, depends exactly where it hits and what the storm is doing when it hits, etc. What would the most comparable storm, as far as current size/strength/longevity to Irma? People keep on pointing to Andrew because of Miami, obviously, but I'm wondering what more similar storms have hit the U.S.

 

Until the winds go lower, this is a larger storm with a stronger wind field, so we are discussing things that haven't happened and even if that does happen wind wise. The surge will be much more substantial.

[HoarfrostHubb]

Curious as to the shape/orientation of Biscayne Bay and how forecast surge will be affected.  To my untrained eyes it looks to be not so good

[jojo762]

5 minutes ago, RUNNAWAYICEBERG said:

Looks very healthy to me with typical fluctuations expected when you get a systematic set of clouds maxing out the atmosphere while traveling 2000+ miles. 

Pretty amazing that this is the first legit strength fluctuation in several days... STILL high-end cat 4/minimal cat 5 at this point... with reintensification looking highly probable as it starts to make its turn, OR as soon as the ERC completes. 

[jasons]

2 minutes ago, tacoman25 said:

What would the most comparable storm, as far as current size/strength/longevity to Irma?

 

Carla. She was monster but thankfully hit a relatively un-populated area. But the damage was horrible well away from the center.

[Crazy4Wx]

1 minute ago, HoarfrostHubb said:

Curious as to the shape/orientation of Biscayne Bay and how forecast surge will be affected.  To my untrained eyes it looks to be not so good

Based on the angle of approach....yeah...it is not so good

[WeatherEmperor]

Does anyone in this thread have the expertise to discuss what might happen via current models with regard to surge / waves 20 miles from the coast on the edge of Boca Raton?  Asking for a friend that is staying because his family refuses to leave.  Thanks.

[tacoman25]

6 minutes ago, andyhb said:

Well with it approaching a large, low lying metropolitan area (not to mention having spent a very long time as a Cat 5), it's really just that.

Thanks for addressing the question. So a very large Cat 3 that's been a major hurricane for a long time is actually more dangerous than a short-lived, landfalling Cat 5?

If that's the case, does it really matters that much if this storm has 180 mph or 140 mph core winds when she finally arrives? Of course the higher winds will do more damage in a localized area, but sounds like that's not the main threat anyway.

 

[LakeEffectKing]

I bet we see (later tonight or tomorrow morning) a deterioration of the eye structure as the final stages of the EWRC occur.  You will then end up with probably a 25% larger diameter eye sometime tomorrow....then...tomorrow night, barring a dive into Cuba, over tons of oceanic heat content, before any appreciable shear, we will see pressures drop begin to drop, and winds MAY come back a bit....but I'm not so sure about that....

[andyhb]

5 minutes ago, tacoman25 said:

Thanks for addressing the question. So a very large Cat 3 that's been a major hurricane for a long time is actually more dangerous than a short-lived, landfalling Cat 5?

If that's the case, does it really matters that much if this storm has 180 mph or 140 mph core winds when she finally arrives? Of course the higher winds will do more damage in a localized area, but sounds like that's not the main threat anyway.

In the grand scheme of things basically no, in a localized area yes of course (like Homestead with Andrew). If you look at a solution like the 12z Euro spreading 100-150 mph gusts over basically the entire southern portion of the FL Peninsula, I would certainly consider that worse than Andrew's overall impacts (even just factoring in the wind).

[Amped]

9 minutes ago, tacoman25 said:

Yeah, I'm not sure a bigger hurricane is necessarily a more damaging one. People seem to be focused on the fact that Irma is so much bigger than Andrew, a storm that was very powerful and damaging. I would be interested to hear from the pros if larger hurricanes actually tend to do more damage than more compact ones, or vice versa.

I realize that larger wind fields are more likely to create a bigger storm surge, but there's more to it than that.

And this storm is also going to parallel the coast,, instead of hitting perpendicular like Andrew.  This can greatly increase the area effected by surge and wind.  Imagine it makes landfall at 160mph in Key largo and is still 100mph all the way to Georgia.  That as bad as as every major hurricane that hit Florida east coast in the past 100 years all hitting at once.

[tacoman25]

5 minutes ago, Stebo said:

Until the winds go lower, this is a larger storm with a stronger wind field, so we are discussing things that haven't happened and even if that does happen wind wise. The surge will be much more substantial.

I hear ya, was mainly just looking for examples of a storm this size that's hit the U.S., since Andrew was so dissimilar in that respect.

[cwc]

13 minutes ago, Coach McGuirk said:

Hurricane Andrew was small and strong and got cat 5 status at landfall.

I lived on 152 st during Andrew.  I kept waiting for the eye so we could secure our blown out windows.  It never came....

[Wild Weather Monger]

While Irma is taking a wee break in intensity as she gets ready to ramp up again when she nears the NW turn as modeled for days now, Irma is still building on her WORLD record as the strongest for longest tropical cyclone.  Fascinating storm!

http://uproxx.com/news/hurricane-irma-strongest-storm-in-history/

 

[the ghost of leroy]

Just now, andyhb said:

In the grand scheme of things basically no, in a localized area yes of course (like Homestead with Andrew). If you look at a solution like the 12z Euro spreading 100-150 mph gusts over basically the entire southern portion of the FL Peninsula, I would certainly consider that worse than Andrew's overall impacts (even just factoring in the wind).

imo it depends on property damage vs lives lost.  a tight core thing like andrew that is truly nuclear will usually kill more people than something looser but still pretty bad.  the opposite is true when you just tally up insured losses since area of damage matters more.

[tacoman25]

6 minutes ago, jasons said:

Carla. She was monster but thankfully hit a relatively un-populated area. But the damage was horrible well away from the center.

Thanks! I'll have to research that one.

[78Blizzard]

9 minutes ago, LakeEffectKing said:

I bet we see (later tonight or tomorrow morning) a deterioration of the eye structure as the final stages of the EWRC occur.  You will then end up with probably a 25% larger diameter eye sometime tomorrow....then...tomorrow night, barring a dive into Cuba, over tons of oceanic heat content, before any appreciable shear, we will see pressures drop begin to drop, and winds MAY come back a bit....but I'm not so sure about that....

Didn't you say just 2-3 hours ago that you thought we would see a pressure drop of 15+mb in the next 12 hours or so.  Isn't that at odds with seeing a deterioration of the eye structure during the erc?

[CheeselandSkies]

6 minutes ago, tacoman25 said:

Thanks for addressing the question. So a very large Cat 3 that's been a major hurricane for a long time is actually more dangerous than a short-lived, landfalling Cat 5?

 

This is a moot point because Irma has been, and remains a 5. As strong or stronger than Andrew over a larger area. No reason it can't remain at least a high-end 4 up until landfall. Yeah there might be some dry air or shear here and there but not enough to disrupt the core in short order, and SSTs along the projected path are as favorable as they get.

[LakeEffectKing]

1 minute ago, 78Blizzard said:

Didn't you say just a 2-3 hours ago that you thought we would see a pressure drop of 15+mb in the next 12 hours or so.  Isn't that at odds with seeing a deterioration of the eye structure during the erc?

Yeah...until I saw the microwave pass an hour or so ago....

[mattb65]

5 minutes ago, tacoman25 said:

I hear ya, was mainly just looking for examples of a storm this size that's hit the U.S., since Andrew was so dissimilar in that respect.

Hate to respond and further derail this thread but Katrina is the obvious case study for the question you keep posing.

[Bostonseminole]

4 minutes ago, cwc said:

I lived on 152 st during Andrew.  I kept waiting for the eye so we could secure our blown out windows.  It never came....

I lived on 112st/132av.e.. never saw the eye either.. was brutal - no far from country walk

[OUGrad05]

2 minutes ago, CheeselandSkies said:

This is a moot point because Irma has been, and remains a 5. As strong or stronger than Andrew over a larger area. No reason it can't remain at least a high-end 4 up until landfall. Yeah there might be some dry air or shear here and there but not enough to disrupt the core in short order, and SSTs along the projected path are as favorable as they get.

It seems a real possibility Irma could be a 5 and maybe a strengthening 5 at landfall.  The surge she'll be carrying with her will be mammoth.  

[winterymix]

10 minutes ago, WeatherEmperor said:

Does anyone in this thread have the expertise to discuss what might happen via current models with regard to surge / waves 20 miles from the coast on the edge of Boca Raton?  Asking for a friend that is staying because his family refuses to leave.  Thanks.

He can always say to his family that if they aren't leaving, use a Sharpie to each put their full name and SS# on forearm.

[tacoman25]

7 minutes ago, CheeselandSkies said:

This is a moot point because Irma has been, and remains a 5. As strong or stronger than Andrew over a larger area. No reason it can't remain at least a high-end 4 up until landfall. Yeah there might be some dry air or shear here and there but not enough to disrupt the core in short order, and SSTs along the projected path are as favorable as they get.

We're all discussing hypotheticals here. We don't know what strength it will hit, we just know it's a very large, long-lived storm that has been very strong for unusually long. Also, I'm discussing storms in general, not just this one.

So my hypothetical is no more moot than yours. 

[tacoman25]

3 minutes ago, mattb65 said:

Hate to respond and further derail this thread but Katrina is the obvious case study for the question you keep posing.

In some ways, yes, but that was a much shorter-lived storm.

It's just fascinating to me, because there are so many variables at play here. And no one really knows how it will play out.

 

[cwc]

2 minutes ago, Bostonseminole said:

I lived on 112st/132av.e.. never saw the eye either.. was brutal - no far from country walk

The pisser is my daughter lives in Tampa now.  She may have a better story to tell than I.

Given that, not rooting for too much of a west movement here.  I know that this whole thing depends on the strength of the ridge.  Just dont want it to build too far west...

[Wild Weather Monger]

FWIW, 00z NAM is substantially NE of it's 18Z position at 36 hours.  Looks set to stay E off coast.

[Crazieman]

Just now, Wild Weather Monger said:

FWIW, 00z NAM is substantially NE of it's 18Z position at 36 hours.  Looks set to stay E off coast.

NAM's less than reliable on tropical systems.  A data point nonetheless.

[Wild Weather Monger]

Just now, Crazieman said:

NAM's less than reliable on tropical systems.  A data point nonetheless.

No doubt.  I only mentioned it because the change was quite large, and is in the short term period.

[RU848789]

Forgive me if this has already been discussed, but I've been away from my computer most of the day (family stuff) and there's no way I'm sifting through a few dozen new pages of posts.  Anyway, here's a sobering thought - we know that forecasts of intensity are much less accurate than track forecasts.  What if Irma doesn't weaken to 150 mph at landfall, as currently projected? I know it'll interact a bit with Cuba with some of the circulation over land, but it's also going over some of the warmest waters (near 90F) on the planet right now.  I can't even imagine 175 mph winds at landfall in South Florida (150 mph is bad enough).  

 

It's also worth keeping in mind that wind damage/force is not linear with wind speed - it's an exponential function (cubic).  Therefore, a 150 mph wind is 20% stronger than a 125 mph wind. but the destructive power of a 150 mph wind compared to a 125 mph wind is actually 73% greater (20% more is actually 1.2X and 1.2 cubed is 1.73 or 73% more). For example, Hurricane Andrew’s sustained winds of 165 mph were 160% more powerful than Hurricane Katrina’s sustained winds of 120 mph at coastal Mississippi.

 

http://hurricanescience.org/society/impacts/windsatlandfall/