SATCAST: satellite nowcasts of new storms

The SATCAST algorithm produces 0–1 hour forecasts (“nowcasts”) of new storms, specifically the occurrence of radar echoes of 35 dBZ or greater, which indicates a heavy rain shower. Some of these storms will produce lightning.

The colored objects on the maps are growing cumulus clouds in GOES satellite imagery. Their growth is monitored over successive images taken 7–15 minutes apart, using infrared temperature fields. The infrared fields help measure cloud growth rates, cloud depth, and whether a cloud has ice or water particles at its top. The transition to ice usually leads to more precipitation and suggests that lightning may occur.

The colors, called “strength of signal” (SS), show the increasing likelihood that a 35 dBZ echo (a heavy rain shower) will occur from a given cloud object. Objects with SS values below 40 (blue colors) are relatively undeveloped clouds, or cumulus clouds with small dimensions, and are less likely to produce significant rain in the next 30–60 minutes. Warmer colors (orange and red) indicate taller, rapidly growing cumulus clouds that have a greater than 75–80% chance of becoming a storm in the next 30–60 minutes. Note the motion of an object to estimate where on the ground the rain will fall.

Color key: probability of convective initiation

• SC (snow contamination)
• ≤29%
• 30%
• 40%
• 50%
• 60%
• 70%
• 80%
• ≥90%

Current products

• GOES East: full domain and nine regional loops for the central and eastern United States
• GOES East severe convective initiation loop
• GOES West: full domain and four regional loops for the western United States (not currently updated)

Learn more

Start with the frequently asked questions, then the narrated product training. Research behind the algorithm is listed under Publications.