STORM2K

I remember when Hurricane Lili was heading towards Louisiana as a Category 4 hurricane with 145 winds, then suddenly it weakened into a Category 1 hurricane. I wonder what caused the hurricane to weaken suddenly?

Same thing that caused Opal, Ivan, Katrina, Rita and a host of others to do the same. Dry air off the landmass plus increasing shear.

Steve

Aslkahuna wrote:Same thing that caused Opal, Ivan, Katrina, Rita and a host of others to do the same. Dry air off the landmass plus increasing shear.

Steve

I see. I notices Lili weakened a lot faster than Opal, Ivan, Katrina, and Rita. Lili was a lot smaller than those hurricanes.

Small hurricanes tend to change intensity faster than large ones. Less mass to speed up or slow down.

It was the many prayers said to Our Lady of Prompt Succor and novenas said by the many catholics of south louisiana j/k

Aslkahuna wrote:Small hurricanes tend to change intensity faster than large ones. Less mass to speed up or slow down.

That would explain why Katrina despite having low pressure, the wind intensity did not catch up due to its expanding size. Hurricane Katrina I remember started as small and exploded into a monster.

Aslkahuna wrote:Small hurricanes tend to change intensity faster than large ones. Less mass to speed up or slow down.

This also shows as Large Hurricanes wind down slower after landfall.

Ptarmigan wrote:
That would explain why Katrina despite having low pressure, the wind intensity did not catch up due to its expanding size. Hurricane Katrina I remember started as small and exploded into a monster.

Note that it's the pressure gradient (pressure drop over a specific distance) that produces the wind in hurricanes, not just the lower pressure itself. A tornado can have over 200 mph winds but the pressure inside may only be in the 950mb range. Generally, a smaller hurricane with the same pressure as a larger hurricane will have stronger winds due to the steeper pressure gradient. Katrina's winds would never "catch up", as the pressure drop was over a very large distance.

wxman57 wrote:
Note that it's the pressure gradient (pressure drop over a specific distance) that produces the wind in hurricanes, not just the lower pressure itself. A tornado can have over 200 mph winds but the pressure inside may only be in the 950mb range. Generally, a smaller hurricane with the same pressure as a larger hurricane will have stronger winds due to the steeper pressure gradient. Katrina's winds would never "catch up", as the pressure drop was over a very large distance.

Kinda like elevation gradients. Closer it is, the steeper it is. Further the gradient, the less steeper it is. It would be interesting to measure the pressure inside a tornado.

Ptarmigan wrote:

wxman57 wrote:
Note that it's the pressure gradient (pressure drop over a specific distance) that produces the wind in hurricanes, not just the lower pressure itself. A tornado can have over 200 mph winds but the pressure inside may only be in the 950mb range. Generally, a smaller hurricane with the same pressure as a larger hurricane will have stronger winds due to the steeper pressure gradient. Katrina's winds would never "catch up", as the pressure drop was over a very large distance.

Kinda like elevation gradients. Closer it is, the steeper it is. Further the gradient, the less steeper it is. It would be interesting to measure the pressure inside a tornado.

One of the hurricane chasers got an instrument package and camera inside a tornado last year. It was on a National Geographic special. I believe the barograph measured about a 50mb drop inside the tornado, and that drop produced winds of around Cat 5 hurricane strength. Pressure dop per unit distance is the key to wind speeds surrounding a low center (tornado or hurricane). The absolute value of pressure alone won't tell you how strong the wind will be in a hurricane.

wxman57 wrote:
One of the hurricane chasers got an instrument package and camera inside a tornado last year. It was on a National Geographic special. I believe the barograph measured about a 50mb drop inside the tornado, and that drop produced winds of around Cat 5 hurricane strength. Pressure dop per unit distance is the key to wind speeds surrounding a low center (tornado or hurricane). The absolute value of pressure alone won't tell you how strong the wind will be in a hurricane.

Tornados are much smaller than a hurricane for sure. The largest tornado I believe is about 1 mile wide.