Hurricanes versus north pacific storms.

[ppragman]

So, I recently experienced my first "graze" with a hurricane out here in Hawaii and noticed something weird. So the pressure wasn't really that low, but the winds were ripping on the charts towards the center of the storm. Here's what they're saying it's doing right now that she's mellowed out a bit:

Issued at 500 PM HST TUE OCT 21 2014
SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...21.9N 166.4W
ABOUT 140 MI...220 KM S OF FRENCH FRIGATE SHOALS
ABOUT 450 MI...720 KM W OF LIHUE HAWAII
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES

This low down in South East Alaska has lower pressure but seems to have lower winds. Why is that - are the isobars just jam packed together super tight in a hurricane? Is there something about the greater Coriolis force as you approach the pole that changes the dynamic of things? Is it because of the sea temperature? Why can a hurricane have higher winds at a given pressure than storms I've seen closer to the pole?

 

[Cptnchia]

40MPH winds make it a Tropical Storm, gotta be 74MPH or better to rate hurricane. As for the winds, I would say you are correct with regards to the isobars.

 

[flyboy6585]

Lower pressure doesn't mean higher wind speeds, it has to do with the gradient (or closeness) of the isobars. If there is a large pressure change over a relatively small distance (ie. isobars very close together) then the wind speeds will be higher regardless of what the overall minimum pressure is. Likewise, if the pressure is small over a relatively large area the winds will be comparatively light.

 

[ppragman]

Lower pressure doesn't mean higher wind speeds, it has to do with the gradient (or closeness) of the isobars. If there is a large pressure change over a relatively small distance (ie. isobars very close together) then the wind speeds will be higher regardless of what the overall minimum pressure is. Likewise, if the pressure is small over a relatively large area the winds will be comparatively light.

So the isobars in a tropical storm or hurricane must just be super super tight together.

Edit: I should add that in my limited experience lower pressure has always resulted in tighter isobars and thus faster winds

 

[flyboy6585]

You can see the difference in the isobars around the hurricane. In North Carolina the winds are around 15kts, as you get into northern Georgia they are around 20kts and the isobars get a little closer, as you get toward the hurricane you see the bars get closer and the barbs show 40kts, as you get closer to the center of the hurricane you can see the isobars get much much closer together.

 

[Capt. Chaos]

Pretty mellow up here today, you should have snagged yesterday's chart. CB's TS's LLWS etc. Pretty common to be in 70kts+ winds at 8-9k and 30-40 at the surface. We regularly are shooting approaches into PAKW with 75kts on the tail at the procedure turn.

The big storms are so common that everything is built to compensate, its just Tuesday and is blowing and raining as usuall.