Tropical cyclone rainfall forecasting

Climatology and persistence models, such as r-CLIPER, can create a baseline for tropical cyclone rainfall forecast skill.

Simplified forecast models, such as the Kraft technique and the eight and sixteen-inch rules, can create quick and simple rainfall forecasts, but come with a variety of assumptions which may not be true, such as assuming average forward motion, average storm size, and a knowledge of the rainfall observing network the tropical cyclone is moving towards.

The forecast method of TRaP assumes that the rainfall structure the tropical cyclone currently has changes little over the next 24 hours.

A tropical cyclone's highest rainfall rates can lie in the right rear quadrant within a training (non-moving) inflow band.

Riehl calculated that 33.97 inches (863 mm) of rainfall per day can be expected within one-half degree, or 35 miles (56 km), of the center of a mature tropical cyclone.

[12] This heavy rainfall can lead to landslides, which still cause significant loss of life such as seen during Hurricane Mitch in Central America, where several thousand perished.

[15] This technique's main flaw is that it assumes a steady state tropical cyclone which undergoes little structural change with time, which is why it is only run forward for 24 hours into the future.

Since forecast models output their information on a grid, they only give a general idea as to the areal coverage of moderate to heavy rainfall.

No current forecast models run at a small enough grid scale (1 km or smaller) to be able to detect the absolute maxima measured within tropical cyclones.

[22] This rule works, even in other countries, as long as a tropical cyclone is moving and only the first order or synoptic station network (with observations spaced about 60 miles (97 km) apart) are used to derive storm totals.