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Started By
Message
re: Storm Tracking Thread: Post Tropical Storm Hermine
Posted on 8/30/16 at 9:06 am to tiger91
Posted on 8/30/16 at 9:06 am to tiger91
quote:
What's significant about 90 west??
If it gets to 90 W it's west of New Orleans way off current trajectory. Lack of development at upper level has helped the storm avoid this NW track to date.
0
Posted on 8/30/16 at 9:07 am to rds dc
I would get on my board and catch some waves in this storm.
Posted on 8/30/16 at 9:32 am to Rakim
4km NAM bringing this thing down to a pressure of 930 mb while still in the Gulf.
Posted on 8/30/16 at 9:34 am to G Vice
quote:
diffusive scales
quote:
Yea....I got nothing.
They're easy enough for me to define; however, it's a bit surprising that in a 140+ page thread where many people have been talking about the effects of convection, nobody seems to have a clue about diffusion.
The governing equations for all storms are nothing more than a balance between advective (inertia of the fluid), diffusive (dissipation of inertia), and external (gravity, Coriolis, etc.) forces.
ALL of the models being discussed in this entire thread completely ignore the dissipative forces for fluid momentum. They are essentially making the argument that the Reynolds number is infinite. See:
The resulting equations from this assumption are called the Euler equations: LINK.
This is all fine and good once a storm actually contains a closed circular center, a large pressure gradient inwards, and a high magnitude of fluid convection (inertia). This is because the length and time scales of the large inertial forces are driving the storm, not the diffusive length and time scales. The infinite Reynolds number assumption bears some truth in this case.
Now, onto the turbulence. SOME of the models in this thread attempt to not only model the mean fluid quantities, but also include models for the turbulent perturbations within the storm. The turbulent equations are again cast as a balance of turbulent convective (inertia) and turbulent diffusive (dissipation) forces. And again, turbulent diffusion is completely ignored in all of the models in this thread.
So why are the models struggling with TD9? The simple answer is that the Euler equations were not suited for this storm the past week or so. The more involved answer requires a discussion about the inertial and diffusive scales particular to TD9 and the driving potentials of each.
There is also an entirely separate argument regarding the modeling of energy (heat) transport in these storms as well. However, I think I will save that one for another time.
Posted on 8/30/16 at 9:36 am to CFDoc
So where is TD9 going to make landfall?
Posted on 8/30/16 at 9:37 am to CFDoc
TLDR
And oh yea.... Frick that formula
And oh yea.... Frick that formula
Posted on 8/30/16 at 9:37 am to CFDoc
quote:
They're easy enough for me to define; however, it's a bit surprising that in a 140+ page thread where many people have been talking about the effects of convection, nobody seems to have a clue about diffusion.
The governing equations for all storms are nothing more than a balance between advective (inertia of the fluid), diffusive (dissipation of inertia), and external (gravity, Coriolis, etc.) forces.
ALL of the models being discussed in this entire thread completely ignore the dissipative forces for fluid momentum. They are essentially making the argument that the Reynolds number is infinite. See:
The resulting equations from this assumption are called the Euler equations: LINK.
This is all fine and good once a storm actually contains a closed circular center, a large pressure gradient inwards, and a high magnitude of fluid convection (inertia). This is because the length and time scales of the large inertial forces are driving the storm, not the diffusive length and time scales. The infinite Reynolds number assumption bears some truth in this case.
Now, onto the turbulence. SOME of the models in this thread attempt to not only model the mean fluid quantities, but also include models for the turbulent perturbations within the storm. The turbulent equations are again cast as a balance of turbulent convective (inertia) and turbulent diffusive (dissipation) forces. And again, turbulent diffusion is completely ignored in all of the models in this thread.
So why are the models struggling with TD9? The simple answer is that the Euler equations were not suited for this storm the past week or so. The more involved answer requires a discussion about the inertial and diffusive scales particular to TD9 and the driving potentials of each.
There is also an entirely separate argument regarding the modeling of energy (heat) transport in these storms as well. However, I think I will save that one for another time.
Posted on 8/30/16 at 9:38 am to CFDoc
quote:
Storm Tracking Thread: TD9 - Gulf Threat
quote:
diffusive scales
quote:
Yea....I got nothing.
They're easy enough for me to define; however, it's a bit surprising that in a 140+ page thread where many people have been talking about the effects of convection, nobody seems to have a clue about diffusion.
The governing equations for all storms are nothing more than a balance between advective (inertia of the fluid), diffusive (dissipation of inertia), and external (gravity, Coriolis, etc.) forces.
ALL of the models being discussed in this entire thread completely ignore the dissipative forces for fluid momentum. They are essentially making the argument that the Reynolds number is infinite. See:
The resulting equations from this assumption are called the Euler equations: LINK.
This is all fine and good once a storm actually contains a closed circular center, a large pressure gradient inwards, and a high magnitude of fluid convection (inertia). This is because the length and time scales of the large inertial forces are driving the storm, not the diffusive length and time scales. The infinite Reynolds number assumption bears some truth in this case.
Now, onto the turbulence. SOME of the models in this thread attempt to not only model the mean fluid quantities, but also include models for the turbulent perturbations within the storm. The turbulent equations are again cast as a balance of turbulent convective (inertia) and turbulent diffusive (dissipation) forces. And again, turbulent diffusion is completely ignored in all of the models in this thread.
So why are the models struggling with TD9? The simple answer is that the Euler equations were not suited for this storm the past week or so. The more involved answer requires a discussion about the inertial and diffusive scales particular to TD9 and the driving potentials of each.
There is also an entirely separate argument regarding the modeling of energy (heat) transport in these storms as well. However, I think I will save that one for another time.
What.
In the actual frick.
Posted on 8/30/16 at 9:40 am to burdman
Nobody knows.
That's the argument I've been trying to get across to these armchair meteorologist for a couple days now.
That's the argument I've been trying to get across to these armchair meteorologist for a couple days now.
Posted on 8/30/16 at 9:43 am to CFDoc
Well I could have said in two words what you said in 2 million.
Who knows?
Who knows?
Posted on 8/30/16 at 9:43 am to CFDoc
So you are the real meteorologist? All the ones on TV and the ones running these models, and the ones at NHC, they all armchair as well I guess? Are you the only real meteorologist out there? I'm asking cause I barely know how to open my weather channel app.
Posted on 8/30/16 at 9:43 am to CFDoc
Well, I do know that everything has been moving straight West across the Gulf for quite a few days now.
I am apprehensive that this won't take a northerly jog quite so readily as most of the predictions show it to.
I am apprehensive that this won't take a northerly jog quite so readily as most of the predictions show it to.
Posted on 8/30/16 at 9:44 am to burdman
quote:
So where is TD9 going to make landfall?
somewhere between Panama and Key West or won't make landfall at all, with the strength of a Low system to a Cat 5 hurricane.
Posted on 8/30/16 at 9:45 am to theunknownknight
quote:
We will never have a president with that level of swag again.
Posted on 8/30/16 at 9:47 am to Fratigerguy
quote:
All the ones on TV and the ones running these models,
There is no meteorologist, worth a damn, on TV or anywhere else, that's putting near the amount of faith in these models as the people in this thread.
Those guys are well educated and understand the high uncertainty, and just plain stupidity, in telling you where landfall will be for a storm that far out.
Posted on 8/30/16 at 9:52 am to Fratigerguy
He doesn't need to be a met to know that stuff. It's fluids.
Posted on 8/30/16 at 9:52 am to CFDoc
quote:
Nobody knows.
That's the argument I've been trying to get across to these armchair meteorologist for a couple days now.
Sure, no one knows for certain, but you're being disingenuous if you're insinuating that the NHC or other real meteorologists are simply clueless.
ETA: Hell, they list an actual wind speed probability on their website. Places like Cedar Key, FL have a 49% cumulative chance of experience 34kt or higher winds in the next 5 days. That is pretty significant in the realm of forecasting.
This post was edited on 8/30/16 at 9:55 am
Posted on 8/30/16 at 9:55 am to slackster
I'm assuming CFDoc stands for Captian Fluid Doctor so I wouldn't question his knowledge about water things anymore
Posted on 8/30/16 at 9:56 am to slackster
That's why the error cone is there on NHC tracks. No model is perfect, they're all built on assumptions that will cause errors. Of course, just because a model isn't perfect doesn't mean it is not useful. Just that seeing a model run land on some pinpoint landfall is fantasy, but it'll probably be right three days out somewhere in that general area.
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