Extratropical Lows

[Ptarmigan]

How extratropical lows have larger wind fields than hurricanes?

[Hybridstorm_November2001]

Hope I'm not over stepping my bounds here:

Simple Answer -

Because in part the storm loses organized convection in it's inter core. SST and/or (if over land) dry air limits the amount of sustainable latent heat available to maintain the energy input/out put cycle. Look at it as a pin wheel. Remove the center pin, and the pin wheel veins unravel to cover a larger area. They also slow their spin in the process, as the remaining energy is spread out over a bigger circumference.

[Hybridstorm_November2001]

On an interesting side note. If you take all the energy found in the several hundred wide mile circulation of your average hurricane, and squeeze in into an area half a mile or less wide, and the opposite effect as noted above happens. I.E. winds of 75 mph gusting to 100 mph, would equal roughly 250 mph (peak gusts). The reason of course is that the wind has far less area to travel before it completes it's revolution, and thus can reach a much greater speed while traversing a much smaller area.

[Ptarmigan]

On an interesting side note. If you take all the energy found in the several hundred wide mile circulation of your average hurricane, and squeeze in into an area half a mile or less wide, and the opposite effect as noted above happens. I.E. winds of 75 mph gusting to 100 mph, would equal roughly 250 mph (peak gusts). The reason of course is that the wind has far less area to travel before it completes it's revolution, and thus can reach a much greater speed while traversing a much smaller area.

Is there a way to calculate wind speed based on pressure and circulation?

[Aslkahuna]

Yes, there are equations for calculating the gradient wind. Of course with a baroclinic system, you also need to calculate the thermal wind to derive a result close to the actual wind (as well as the isallobaric wind for rapidly deepening ET Lows [Bombs]).

Steve

[Ptarmigan]

Yes, there are equations for calculating the gradient wind. Of course with a baroclinic system, you also need to calculate the thermal wind to derive a result close to the actual wind (as well as the isallobaric wind for rapidly deepening ET Lows [Bombs]).

Steve

Is there a formula for it?

[wxman57]

Yes, there are equations for calculating the gradient wind. Of course with a baroclinic system, you also need to calculate the thermal wind to derive a result close to the actual wind (as well as the isallobaric wind for rapidly deepening ET Lows [Bombs]).

Steve

Is there a formula for it?

Yes, there are formulae that can be used to calculate gradient wind. It's not an easy calculation, though, as it involves a differential equation:

Vgr = -fR/2 ± D1/2
where
D = (fR/2)2 - (R/ρ)(∂p/∂n)

Variables above are explained here:
http://www.applet-magic.com/gradientwind.htm

[Ptarmigan]

Yes, there are formulae that can be used to calculate gradient wind. It's not an easy calculation, though, as it involves a differential equation:

Vgr = -fR/2 ± D1/2
where
D = (fR/2)2 - (R/ρ)(∂p/∂n)

Variables above are explained here:
http://www.applet-magic.com/gradientwind.htm

Thanks. Does ∂=alpha? It looks rather complicated. I found this website where you can get gradient of pressure, latitude, and density of air and get a velocity.
Link

[Aslkahuna]

No that's a lower case delta the symbol used in expressing partial derivatives. Alpha = α

Steve