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The System for
Convection Analysis
and Nowcasting (SCAN) |
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Click here to go to MDL's Homepage
Click here to go to SCAN web page
Operational 0-3 Hour Convective Weather Forecasts:
Real-time Output for the Conterminous United States
Meteorological Development Laboratory
National Weather Service
NOAA
Silver Spring MD
0-3 Hour Rainfall and Lightning Forecasts |
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| Products: | CONUS: | NE US: | SE US: | NC US: | SC US: | NW US: | SW US: |
|---|---|---|---|---|---|---|---|
| Probability of rain > 0.1 inch | X, | X, | X, | X, | X, | X, | X, |
| Probability of rain > 0.5 inch | X, | X, | X, | X, | X, | X, | X, |
| Probability of rain > 1 inch | X, | X, | X, | X, | X, | X, | X, |
| Probability of rain > 2 inches | X, | X, | X, | X, | X, | X, | X, |
| Rainfall amount | X, | X, | X, | X, | X, | X, | X, |
| Probability of CG lightning | X, | X, | X, | X, | X, | X, | X, |
Explanation
These products indicate probabilities of rainfall exceeding various thresholds, rainfall amount forecasts, and probability of cloud-to-ground (CG) lightning:Probability of local rainfall exceeding 0.1, 0.5, 1, and 2 inches;
"Best guess" rainfall amount;
Probability of 2 or more lightning strikes.
These products indicate probabilities of rainfall exceeding certain thresholds, a 'best estimate' peak rainfall amount, and probability of cloud-to-ground 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.
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.
At present the output takes the form of color-coded boxes on county-state map backgrounds. The box format accounts for the fact that the probability and rainfall amount forecasts refer to the maximum rainfall values over the entire box, not at individual points.
More complete documentation includes a full explanation of the model development and performance characteristics.
Graphical Product Availability
These graphic products are generally updated shortly before the start of the valid period, The graphics are produced only on an experimental basis, and routine generation can be 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.
The graphic products on this website are made available to demonstrate operational forecast products. 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.
DISCLAIMER