6/22/2023 0 Comments Key west radar in motionThe sediment may have entered the water from with flood water draining into the sea it may be from storm-eroded beaches or it may be sediment from the ocean floor brought to the surface with the churning of the sea under Wilma’s winds. The Atlantic is bright blue, tainted with sediment. Here, no flooding is obvious, but the image shows signs of run-off. To the east of the park, the wetlands have been drained as cities sprung up. In fact, the line defines the boundary of Everglades National Park in the south. Along the eastern shore of the peninsula, it is as if someone drew a line to mark out the edge of the wetlands from the pale green, grey, and tan grid of cities, including Miami and Fort Lauderdale. Dark squares hint at the possibility of flooded fields, but the presence of water in a few fields in the September image also suggests that some of the flooding may be intentional. Between the Everglades and Lake Okeechobee is a lighter green arch of agricultural land. Elevated roads form pale strips of green through the wetlands, which are dark with water in the wake of the storm. The most obvious flooding is in the Everglades, where the wetlands readily soaked up the downpour. The lower image, taken on September 14, 2005, shows southern Florida under normal conditions. Shown in false color to increase the contrast between water and land, the image presents water in black and blue, vegetation in bright green, and clouds in pale blue and white. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured the top image on October 25, 2005. The Category 3 hurricane brought heavy rain, which caused the inland flooding seen here. Wilma moved from the Gulf of Mexico in the west, over the Everglades, and then pounded the populated eastern shore as it made its exit into the Atlantic. The patterns of flooding shown in this image are more a reflection of land use than the intensity of the storm. 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.Dark pools of water covered sections of Florida the day after Hurricane Wilma cut diagonally the state. 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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