National Weather Service United States Department of Commerce

Back to Spring Safety

Spring Safety Infographics (New)


Winter Precipitation:
Snow: Snowflakes never melt
Sleet: Droplets freeze and form ice before reaching the surface
Freezing Rain: Rain freezes on contact with the surface
Rain: Rain never refreezes
Water is essential for life on Earth. But in large enough quantities, the very substance we drink and use to grow crops can destroy homes, businesses and cause fatalities.

River flooding occurs when river levels rise & overflow their banks or the edges of their main channel and inundate normally dry areas.

River flooding can be caused by heavy rainfall, dam failures, rapid snowmelt and ice jams.

Six Steps to Create a River Model
Hydrologic Cycle: Hydrologists try to understand and simulate the natural hydrologic cycle, which is the intricate combination of many processes such as evaporation, transpiration, precipitation, infiltration, interflow, groundwater storage, and runoff.

Precipitation: Precipitation is the primary input to basin hydrologic processes and serves as the primary driver of hydrologic models. Accurate representation of precipitation input is an important intial step. Small river channel systems are very sensitive to rainfall.

Runoff: The next step is to compute the amount of precipitation that appears in surface water within a relatively short time from the onset of a storm event. This is runoff. Runoff consists of 3 components: 
overland flow, rain falling directly on surface water bodies, and interflow.

Unit Hydrograph: After computing basin runoff, the next step is to calculate a forecast hydrograph in units
of discharge. A hydrograph is a plot of the change of stage or discharge with respect to time. Discharge is the volume of water flowing past a location per unit time and is usually expressed in cubic feet per second (cfs).

Streamflow Data: Scientists use streamflow measurements to capture the vital relationship between discharge (volume flow rate) and stage (height) for a given location. This can only be done by taking streamflow measurements at different river levels and noting the corresponding stages. This relation is called a rating curve.

Routing: Hydrologists analyze and interpret how the water moves once it’s in the river and how a flood wave is modified due to the effects of storage and friction as it moves downstream. So, what happens upstream affects the entire downstream community.
Supercell Tornadoes:
Tornadoes that come from a supercell thunderstorm are the most common, and often the most dangerous. A rotating updraft is a key to the development of a supercell, and eventually a tornado. There are many ideas about how this rotation begins. One way a column of air can begin to rotate is from wind shear – when winds at two different levels above the ground blow at different speeds or in different directions. Once the updraft is rotating and being fed by warm, moist air flowing in at ground level, a tornado can form.

Landspouts, narrow, rope-like condensation funnels that form while the thunderstorm cloud is still growing and there is no rotating updraft. The spinning motion originates near the ground.

Waterspouts, similar to landspouts, except they occur over water.

Gustnadoes, whirls of dust or debris at or near the ground with no condensation funnel, which form along the gust front of a storm.

Dust Devils:
A well-developed dust whirl; usually of short duration, rendered visible by dust, sand, and debris picked up from the ground. Dust devils are best developed on a hot, calm afternoon with clear skies, when intense surface heating causes large temperature differences in the lowest couple hundred feet of the atmosphere.

Fire Whirls:
Much like dust devils, the extreme heat of fires create strong updrafts, near the ground that interact with circulations in the lower atmosphere. Fire whirls are usually about 1 to 3 feet  wide and 50 to 100 feet tall.
Most tsunamis are caused by large earthquakes below or near the ocean floor.
1. A plate shifts abruptly, causing an earthquake, and displacing water.
2. Waves are generated and move out in all directions across the ocean, some traveling as fast as 600 mph.
3. As waves enter shallow water, they compress, their speed slows, and they build in height
4. The wave height increases, and associated currents intensify, becoming a threat to life and property



All Spring Hazard Infographics


Flood Heat Lightning Rip Currents Tornado Tsunami Winter Weather
Flood Heat Lightning Rip Currents Tornado Tsunami Winter Weather