California’s Death Valley will climb above 120 degrees on Friday, and could reach the upper 120s to near 130 degrees this weekend.Phoenix’s record for 110-degree readings lasted 18 days in 1974.Friday, Saturday, Sunday and Monday are all expected to reach 116 degrees or higher. The National Weather Service is forecasting a high of 111 degrees on Tuesday assuming that forecast is realized, the remainder of the week should be sure to hit 110 or greater every day. Monday was expected to be a close call, but Sky Harbor International Airport reached 110. Desert Southwest: Phoenix has logged 11 consecutive days at or above 110 degrees.The nonprofit’s Climate Shift Index, a tool that quantifies how climate change has affected the likelihood of severe weather conditions, rated parts of the states a 5, indicating that the heat is an “exceptional” event. Climate change has made the persistent heat in parts of Texas, the Southwest and Mexico at least five times more likely, according to an analysis from Climate Central.The hottest weather, found beneath it, will affect the Gulf Coast, the southern Plains and the Southwest. By Thursday, the stretched-out heat dome will be anchored over California, but will stretch from the northeastern Pacific Ocean all the way to Florida.In fact, the halfway point of atmospheric mass is now roughly a football field higher in altitude than it ordinarily would be - courtesy of the extreme heat causing air columns to grow. Warm air expands, which means the heat dome is essentially causing a vertical bulge in the atmosphere.In addition to causing a marked warm-up, that also supports ceaseless sunshine, which will heat the air mass even more. Beneath the heat dome, sinking air will heat up and dry out.Think of a heat dome like a force field - it steers away any inclement weather, diverting storm systems and the jet stream northward over the Upper Midwest, Great Lakes and Canada. The instigating heat dome, or ridge of high pressure causing the heat, is expanding and elongating.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. 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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