Calculating Strength

[Ptarmigan]

I wonder if there is a way to calculate sustained winds of a hurricanes. I know lower the pressure, the stronger the winds are. Also, it would depend on the size of the hurricane. For example, Hurricane Andrew had 175 mph winds and a pressure of 922 millibars. On the other hand, Hurricane Katrina had 125 mph winds and a pressure of 920 millibars. Super Typhoon Tip had a pressure of 870 millibars and had sustained winds of 160 to 190 mph.

[wxmann_91]

I know lower the pressure, the stronger the winds are.

Not necessarily. It's based on the pressure gradient. Larger hurricanes tend to have a looser gradient but that's not necessarily 100% correct 100% of the time. Took me some time to realize that after the Katrina fiasco.

There is no way to completely accurately calculate max sustained winds inside a hurricane. The closest thing to it is getting reports from higher levels and then estimating it via a conversion factor. (hurricane hunters and velocity data from radar)

[btangy]

Roughly speaking, the wind speed is directly proportional to the local pressure gradient. Although the minimum pressure of a tropical cyclone/hurricane is correlated with the maximum wind speed, there isn't a clear cut formula relating the two although there are empirical formulas.

The simple answer to your question is that one has to consider how fast the pressure is falling off with decreasing radius, which we don't really know given one needs really dense observations to determine this. What is normally done is to consider the ambient (environmental) pressure surrounding the storm. Generally, the higher the ambient pressure, the stronger the winds are for TCs with the same minimum pressures.

Also, there is no relationship between the size of a hurricane and its intensity. Charley and Andrew were intense but tiny storms, but the W Pacific recently had a huge storm (Bilis) that only was a tropical storm.

[Ptarmigan]

Roughly speaking, the wind speed is directly proportional to the local pressure gradient. Although the minimum pressure of a tropical cyclone/hurricane is correlated with the maximum wind speed, there isn't a clear cut formula relating the two although there are empirical formulas.

The simple answer to your question is that one has to consider how fast the pressure is falling off with decreasing radius, which we don't really know given one needs really dense observations to determine this. What is normally done is to consider the ambient (environmental) pressure surrounding the storm. Generally, the higher the ambient pressure, the stronger the winds are for TCs with the same minimum pressures.

Also, there is no relationship between the size of a hurricane and its intensity. Charley and Andrew were intense but tiny storms, but the W Pacific recently had a huge storm (Bilis) that only was a tropical storm.

I know typhoons can get very large. I read somewhere that Charley is one of the smallest Atlantic hurricane, besides Iris of 2001.

[Ptarmigan]

I know lower the pressure, the stronger the winds are.

Not necessarily. It's based on the pressure gradient. Larger hurricanes tend to have a looser gradient but that's not necessarily 100% correct 100% of the time. Took me some time to realize that after the Katrina fiasco.

There is no way to completely accurately calculate max sustained winds inside a hurricane. The closest thing to it is getting reports from higher levels and then estimating it via a conversion factor. (hurricane hunters and velocity data from radar)

Hurricane Wilma had the lowest pressure, yet at one point hurricane force winds only extended 15 miles from the eye. I wonder if larger the eye, the larger the hurricane force windfield would be.