Rainfall

South Florida Water Management District Weather
10:08AM Thursday, May 16, 2022 (mrn)

Synopsis: An upper-air trough of low pressure extending from the southeast U.S. coast to the eastern Gulf of Mexico will gradually move eastward across Florida today and lie east of the SFMWD by Tuesday. A good supply of moisture and instability immediately ahead of the trough and sufficient daytime heating should cause showers and thunderstorm to form, with southwesterly steering winds favoring the rains over the eastern part of the SFWMD from around Lake Okeechobee southward and eastward through the eastern metropolitan areas. The median areal average rainfall across this region ranges from a quarter to half of an inch, with the 90th percentile or reasonable worst-case scenario in excess of half of an inch. As the trough passes across western areas and the Kissimmee Valley by this afternoon, subsidence (sinking air) and a subsequent drying with low instability should result in essentially no rainfall, or at least little of note. On Tuesday and Wednesday, large-scale subsidence in the wake of the trough is forecast to greatly suppress typical shower and thunderstorm development. However, there should be enough low-level moisture to cause isolated rains to develop along both east and west coast sea breezes on Tuesday and then isolated or widely scattered rains on Wednesday over the interior and the west when the steering winds become easterly to southeasterly. The 10% exceedance on either Tuesday or Wednesday should be no more than about a tenth of an inch. Next, a tropical wave located over the central Caribbean Sea on Tuesday should move into the western Caribbean Thursday and Friday, with its moisture feed beginning to stream northward through the Florida Keys and far southern part of the SFWMD overnight Thursday. The wave’s moisture will also be accompanied by an influx of instability, both ingredient of which should support a large increase of rainfall and rain coverage SFWMD-wide Friday and Saturday. Given the favorable large-scale conditions accompanying the wave passage south of the area, there is likely to be an enhanced risk of locally significant rainfall area wide but especially over the interior of the SFWMD. Although the most best moisture/instability seems as if will have passed by Sunday, southwesterly steering winds and daytime surface heating should still result in a good coverage of rain probably focused over the interior and the east due to southwesterly steering winds ahead of a cold front dropping southward into north Florida by Monday morning next week. For the week ending next Monday morning, total SFWMD rainfall is forecast to be at least normal and probably above normal. Monday: Very warm over parts of the SFWMD> A few showers and isolated thunderstorms developing in the east or southeast before noon. Then scattered to locally numerous afternoon showers and thunderstorms developing south and east of Lake Okeechobee through the southeastern metropolitan areas, some of which could be heavy. Rains could continue to around or after sunset before dissipating over these areas. Then quiet overnight as drier air moves across the entire area. SW to W winds 5 to 15 mph, except S near the east coast. Winds W to WSW 5 to 10 mph overnight. Tuesday: Very warm over the interior. A general lack of much rainfall area wide and far below the daily climatological average. Whatever rains do form should occur during the afternoon to around sunset inland of the east coast along the east-coast sea breeze and inland of the west-coast along the west coast sea breeze through the Kissimmee Valley. Rains diminishing by or during the early evening. Mainly W to WNW winds of 5 to 15 mph, except for E to SE winds developing by the afternoon to early evening along and near the east coast. Wednesday: A continued reduced total amount and rain coverage compared to climatology. Afternoon rains developing over parts of the interior and then over the interior and the west by late afternoon to around sunset. Isolated rains over the far west could produce heavier totals of rain. Rain chances diminishing in the east by afternoon. Mainly E to SE winds of 5 to 15 mph in the east but with W winds of 5 to 15 mph over the west during the afternoon. E to SE winds 5 to 10 mph south of Lake Okeechobee but SW winds 5 to 10 mph north and west of Lake Okeechobee overnight. Thursday: Quiet with essentially no rain in the morning. Then isolated or widely scattered afternoon rains across the SFWMD, with a few embedded heavier rain areas. However, an increase of rains should begin rising from the south into the far southern part of the SFWMD during the afternoon, followed by a good or widespread coverage of rain overnight through the Florida Keys. SSE to S winds 5 to 15 mph during the morning but then E to SE over the eastern part of the SFWMD during the afternoon and W to SW over western areas. SE to S winds area wide overnight. Friday: A large increase of rain area wide, with total rainfall likely well above the daily climatological average. Scattered to numerous showers and thunderstorms producing a widespread coverage of rainfall, some of which could be heavy. Heaviest rains probably over the interior and the west from the afternoon to early evening. An enhanced risk of locally significant rainfall accumulations. Rains diminish late in the evening and then mostly quiet overnight. SE to S winds mainly 5 to 15 mph. Saturday: Total rainfall again probably well above the daily climatological average. A good or widespread coverage of moderately heavy or heavy rains over the interior of the SFWMD but especially around and north of Lake Okeechobee from the afternoon to early evening. An elevated risk of locally significant rainfall over these areas. After evening rains diminish, mainly quiet conditions likely overnight. SE to S winds 5 to 15 mph, except S to SW north of Lake Okeechobee (0.36″). Sunday: Low-confidence forecast. Little rain in the morning, but scattered to locally numerous showers and thunderstorms forming over the interior and the east during the afternoon. Rains diminish during the early evening. SE to S wind 5 to 15 mph, except SW north of Lake Okeechobee, with winds becoming W to NW area wide overnight (0.27″).