Sally's remnants lasted for another day as they moved off the coast of the Southeastern United States, before being absorbed into another extratropical storm on September 18. The storm rapidly weakened after landfall, before transitioning into an extratropical low at 12:00 UTC the next day. Despite this increase in wind shear, it unexpectedly re-intensified, reaching Category 2 status early on September 16, before making landfall at peak intensity at 09:45 UTC on September 16, near Gulf Shores, Alabama, with maximum sustained winds of 110 mph (180 km/h) and a minimum central pressure of 965 millibars (28.5 inHg).
However, an increase in wind shear and upwelling of colder waters halted the intensification and Sally weakened slightly on September 15 before turning slowly northeastward. On September 14, a center reformation into the center of the convection occurred, and data from a hurricane hunter reconnaissance aircraft showed that Sally rapidly intensified into a strong Category 1 hurricane. Moderate northwesterly shear prevented significant intensification for the first two days, but convection continued to grow towards the center and Sally slowly intensified. Early the next day, the depression made landfall at Key Biscayne, and subsequently strengthened into Tropical Storm Sally that afternoon. The system grew a broad area of low-pressure on September 11, and was designated as a tropical depression late that day. The eighteenth named storm, and seventh hurricane of the extremely active 2020 Atlantic hurricane season, Sally developed from an area of disturbed weather which was first monitored over the Bahamas on September 10. state of Alabama since Ivan in 2004, coincidentally on the same date in the same place. Hurricane Sally was a destructive and slow-moving Atlantic hurricane, which was the first hurricane to make landfall in the U.S. Part of the 2020 Atlantic hurricane season 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.Hurricane Sally rapidly intensifying before landfall in Alabama on September 16 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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