Experimental 0-3 Hour Convective Weather Forecast Products

Real-time Output for the Conterminous United States
| Explanation | Availability | Contacts |

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Choose a region
and a product:

Prob. 0.1 inch

Prob. 0.5 inch

Prob. 1 inch

Prob. 2 inches

Rainfall amount

Prob. CG ltg


These products indicate probabilities of rainfall exceeding certain thresholds, a 'best estimate' peak rainfall amount, and probability of cloud-to-ground (CG) lightning. Rainfall forecasts are for the highest rainfall amounts within square regions 40 km (~20 miles) on a side. Lightning forecasts are for the probability of two or more strikes within the same regions.

Probabilities are for 3-hour rainfall exceeding 0.1, 0.5, 1, and 2 inches (approximately 2.5, 12.5, 25, and 50 mm). Rainfall amount forecasts are for rainfall in the categories 0.1-0.49, 0.5-0.99, 1-1.99, and 2+ inches.

The algorithm that generates the forecasts is slated for implementation within the National Weather Service's Advanced Weather Interactive Processing System (AWIPS), which is used at field offices and national forecast centers.

Input to the products includes a national radar composite, infrared satellite imagery, cloud-to-ground lightning strike observations, and numerical weather prediction model forecasts. All data are input to an extrapolative/statistical algorithm that analyzes the intensity, position, and short-term movement of rainfall and convective systems, and general atmospheric conditions (humidity, stability, and vertical motion) conducive to rain.

The probabilistic output takes the form of color-filled contours on county-state map backgrounds. Categorical amount forecasts take the form of color-filled boxes. The box format accounts for the fact that the rainfall amount forecasts refer to the maximum rainfall values anywhere within the entire box, not the amount at any one place. For ease of viewing, the output for the conterminous United States is presented in six overlapping sector maps.

Forecasts are updated at approximately 0:55 each hour, and cover the succeeding 3-hour period. Production can be interrupted due to communications outages or system maintenance downtime. Problems will generally be corrected only during regular business hours.

More complete documentation includes a full explanation of the model development and performance characteristics.

Product availability

These products are generally updated 5-10 minutes before the start of the valid period, which is at the top of the hour. They are produced only on an experimental basis, and are interrupted by communications outages or system maintenance procedures.

Interruptions will generally be corrected only during working hours between Monday and Friday.

Product valid times

Product valid times are expressed in Universal Coordinated Time (UTC), which is 5 hours ahead of Eastern Standard Time (EST) and 4 hours ahead of Eastern Daylight Time (EDT). Thus 12:15 UTC is 07:15 EST (7:15AM EST) or 08:15 EDT. The date-time 01:30 UTC, 20 May 1997 corresponds to 21:30 (9:30PM) EDT, 19 May 1997.

These products are made available experimentally to demonstrate evolving capabilities of AWIPS. They are not intended to replace official forecasts and warnings. Always rely on NOAA Weather Radio and the broadcast media for official forecasts and warnings.


Questions and comments about the experimental products:
MDL Webmaster
Meteorological Development Laboratory
National Weather Service
Silver Spring MD

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National Weather Service
Last Modified: 13 Oct 2000, RLS.