The strength of tornadoes is measured by the Fujita scale. This forces the air to move upward and can cause it to rotate due to the wind on the ground. However, tornadoes may also form when two different air masses collide. Especially strong tornadoes are formed in this way. Due to the temperature differences within the cloud, strong updrafts and downdrafts develop, which results in a tornado and heavy precipitation. This is a particularly large and high thundercloud. Tornadoes can occur in conjunction with a supercell. There are two ways in which tornadoes can form. Until today, the formation of tornadoes has not been researched thoroughly. At the very latest when the tornado sirens sound, you should quickly get to safety.Īlong with hurricanes, tornadoes are among the most powerful storms in the world and can reach wind speeds of up to 450 km/h. These are also an indicator for the formation of a tornado. As soon as there are first signs of a thunderstorm, hail, strong winds, and rain, you should not take your eyes off the tornado tracker.Īlso, watch the sky and scan it for rotating clouds and cloud columns. Tornadoes can cause severe damage along their route and can occur very unexpectedly. During the tornado season, the center of gravity of the tornado areas moves from the southeast (Great Plains in Oklahoma) more and more towards the north (Illinois and Indiana).Įspecially in times of tornado season you should be very attentive and monitor the weather situation regularly. Most tornadoes occur in the month of May. The tornado season starts in March and lasts until the end of July. It was discovered that the tornado already forms near the ground before it starts to rotate. This assumption, however, has been disproved by extensive research conducted by the American Geophysical Union. This visible column of air is called a tornado.įor a long time, it was assumed that tornadoes form from the sky downward toward the ground. These air masses can rotate so strongly during their formation that an air column is formed. All recommended measures of NOAA can be found briefly and clearly here.Ī tornado is the result of rotating air masses. If you are in an area that lies within this red zone, you should take protective measures as soon as possible (e.g., seek shelter). You can recognize current sightings by a red marker on the map. The second map compiles the current tornado sightings for you. Even with low probabilities of 5% and below, you should definitely keep an eye on the weather situation. You can also recognize the probability by the coloring. Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.The first map shows you the probability of one or more tornadoes. Hail is a good reflector of energy and will return very high dBZ values. These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rainrates which are associated to the dBZ values. The higher the dBZ, the stronger the rainrate. Typically, light rain is occurring when the dBZ value reaches 20. The scale of dBZ values is also related to the intensity of rainfall. The value of the dBZ depends upon the mode the radar is in at the time the image was created. Notice the color on each scale remains the same in both operational modes, only the values change. The other scale (near left) represents dBZ values when the radar is in precipitation mode (dBZ values from 5 to 75). One scale (far left) represents dBZ values when the radar is in clear air mode (dBZ values from -28 to +28). Each reflectivity image you see includes one of two color scales. The dBZ values increase as the strength of the signal returned to the radar increases. So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used. Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong). "Reflectivity" is the amount of transmitted power returned to the radar receiver. The colors are the different echo intensities (reflectivity) measured in dBZ (decibels of Z) during each elevation scan.
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