Humidity Levels and TC Intensity

[brunota2003]

I have a question that puzzles me about the relationship between humidity and storms. Relative humidity is the measure of the amount of water vapor in the air, compared to how much water vapor the air can hold. When it is 100%, the column of air is saturated and can no longer hold more water.

Are strong [thunder]storms more likely to form when the humidity is closer to 100%, 50% or near 0%? Obviously if the humidity is near zero, there is not enough water vapor for the storm...but is there a such thing as too much? If the column is saturated, wouldn't that prohibit updrafts and result in possibly rain?

So how important is humidity to the intensity of a TC? If the air out in front of a TC that is being funneled into it is super humid (ie greater than say 85%), could it potentially choke off the hurricane and weaken it by choking up the updrafts in the eyewall?

If the air is dry, it'll help either keep the storm in check (same intensity) or weaken it, depending on how dry it is...correct?

Obviously where the clouds are, the air is at 100%. But down towards the surface?

[theavocado]

The one factor you are forgetting about is when water comes out of solution from the atmosphere, it releases latent heat. So, when moisture laden air starts to rise and expand, the water comes out of solution and the air warms. As the air warms, it becomes more bouyant than the surrounding air and rises faster, and then releases more moisture faster, etc, etc.

So, the more moist the air, the sooner it can start rising along the moist adiabat, the sooner it can start gaining latent heat, and the faster and more intense the convection can be.

So, to answer your question, close to, if not at, 100% relative humidity is best for development.

[brunota2003]

Thanks...another question I'm wondering about is the relationship between the outer bands and the inner core.

Obviously it takes a lot longer for the outer bands to complete one rotation than it would take the inner cord to. The outer bands, in order to keep up, would have to rotate a lot faster than the inner core...if the outer bands fell behind and got tangled up with the inflow, could that potentially cause a disruption of the system itself? The air could end up rain cooled, being sucked into the system, disturbing the delicate warm core.

Or would that be just a drop in the bucket for the storm? I'm trying to picture it in my head, but the scale and my lack of knowledge is too compounding...so I'm going off of what I know from regular storms...if the updraft of a supercell pulls in rain cooled air, it weakens or completely falls apart...tho supercells are not dependent upon latent heat release.

At what point does the inflow rise up into the system? Anywhere it pleases?

Just the ramblings of a tired person who is only a year out of high school and doesn't know much

[brunota2003]

Yes, you are correct. Hurricanes rely on the latent heat of condensation as the energy source to fuel them. If the air is already saturated it can not evaporate moisture from the ocean to form the needed clouds. Ideally, a relative humidity of about 80% near the ocean surface allows for the development of clouds. If the air is too dry, then you need to evaporate a lot of water to add to the vapor in the air. Typically, though the air in the boundary layer of developing storms is not saturated, except in regions where it is already raining. Dry air at mid-levels can also be destructive to the development of storms while moist air at these levels is more favorable, even if it is at or near saturation.

Michael

On Jul 29, 2009, at 6:20 PM, Timmy Bruno wrote:

I have a question regarding humidity levels and TC intensity. I know that dry air causes hurricanes to weaken, robbing them of much needed moisture...but is there a such thing as too much moisture when it comes to tropical cyclones? If it is pulling in air that is saturated or nearly saturated, could it potentially weaken the cyclone's updrafts, which in turn would weaken the system?

Is there an ideal zone of relative humidity percentages that would cause a hurricane to strengthen? (Probably 50 to 80% if I had to guess). Obviously the air temperatures can change, causing the humidity levels to change as well, but just had that question.

Bruno