. When the radius of recurvature of a storm is greater than 300 miles, it will not decelerate and may even accelerate. The storm will slowdown if the radius of recurvature is less than 300 miles. In general, when the radius of recurvature is large, it is usually very uniform. A small radius will occur along a brief portion of the track. (See fig. 11-2.)

. A large radius of recurvature is to be expected if the high northeast of the tropical cyclone has a vertical axis (fig. 11-3 (A)). This will occur when long waves are stationary.

The following rules refer to short-term (24 hours or less) forecasting:

. Tropical cyclones move toward the area of greatest surface pressure falls (12- to 24-hour pressure change).

Figure 11-2.-(A) Recurvature at a constant speed; (B) First decelerating and then accelerating.

Figure 11-3.-Surface flow pattern (dashed line) and 300- to 200-hPa flow pattern (solid lines). (A) Corresponds to track (A) in figure 11-2; (B) Corresponds to track (B) in figure 11-2.

. Tropical cyclones move toward the area where the surface pressure falls increase most rapidly with time. For calculation, 3-hourly reports are necessary. Take, for example, the 24-hour pressure change at 1800 and subtract it from the 24-hour pressure change at 1500. This gives the acceleration of the pressure fall. If this quantity is computed for a network of stations and isolines are drawn for a suitable interval, the negative center helps to pinpoint the expected cyclone position. This rule is used at intervals of 12 hours or less, and is especially helpful in determining the precise place of landfall for a storm that is just offshore.

This information is now available on CD in Adobe PDF Printable Format

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing