Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Alternative expression for the maximum potential intensity of tropical
  cyclones   Emanuel's concept of maximum potential intensity (E-PI) estimates the maximum
velocity of tropical cyclones from environmental parameters. At the point of
maximum wind, E-PI's key equation relates proportionally the centrifugal
acceleration (squared maximum velocity divided by radius) to the radial
gradient of saturated moist entropy. The proportionality coefficient depends on
the outflow temperature. Here it is shown that a different relationship between
the same quantities derives straightforwardly from the gradient-wind balance
and the definition of entropy, with the proportionality coefficient depending
on the radial gradient of local air temperature. The robust alternative reveals
a previously unexplored constraint: for E-PI to be valid, the outflow
temperature should be a function of the radial temperature gradient at the
point of maximum wind. When the air is horizontally isothermal (which, as we
argue, is not an uncommon condition), this constraint cannot be satisfied, and
E-PI's key equation underestimates the squared maximum velocity by
approximately twofold. This explains "superintensity" (maximum wind speeds
exceeding E-PI). The new formulation predicts less superintensity at higher
temperatures, corroborating recent numerical simulations. Previous analyses are
re-evaluated to reveal inconsistent support for the explanation of
superintensity by supergradient winds alone. In Hurricane Isabel 2003, maximum
superintensity is found to be associated with minimal gradient-wind imbalance.
Modified to diagnostically account for supergradient winds, the new formulation
shows that air temperature increasing towards the storm center can mask the
effect of gradient-wind imbalance, thus reducing "superintensity" and formally
bringing E-PI closer to observations. The implications of these findings for
assessing real storms are discussed.

25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex