Extrapolation of surface winds from flight-level data depends based upon any given storm -- no two storms are alike -- as well as the level at which the winds were reported. Inside of the eyewall, the reduction factor from 700mb is generally 0.91. With Rita, it seems to be a bit closer to 1.0 right now given the available data.
The temperature differential between the eye and eyewall is a measure of the efficiency of the storm and its intensity. Simply put, the subsidence within the eye can be used as a proxy for relative storm efficiency and intensity. Subsidence generally leads to heating; thus, you see temperatures in the eye warmer than those outside of it. The greater the differential, the greater the subsidence and the greater the intensity of the storm. It should be noted that the subsidence in the eye is a necessary response to the strong rising motion in the eyewall and away from the center in the convective moat & feeder bands.
The 700mb height can be used as a measure of the storm's intensity at the surface and in the lower levels. Generally, 700mb heights average around or just above 3000m. Lower heights generally lead to lower pressure and thus a more intense storm; with Rita, we haven't seen 700mb heights being all too low quite yet -- most recent of 2847m is fairly low, but nothing like the 2200-2400m seen with Katrina. It's not hard and fast, however, and will vary from storm to storm.
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