Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 17 2023 01:34:57 FOUS30 KWBC 170134 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 834 PM EST Thu Nov 16 2023 Day 1 Valid 01Z Fri Nov 17 2023 - 12Z Fri Nov 17 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE EAST-CENTRAL FLORIDA... ....01Z Update... A single line of cells has rapidly intensified this evening just south of Palm Bay, through Fellsmere and west of Sebastian. Strong moisture advection from the surface through 850 is pumping keeping plentiful Gulf stream moisture westward into the coast. Meanwhile, a strong shortwave trough evident on satellite is bringing quite a bit of upper level dry air over the storms at the surface. Normally this would lead to a decrease in storm intensity, but that dry air in the upper levels is increasing the instability the storms need to sustain themselves. Further, SPC mesoanalysis shows an incredible "bullseye" of moisture convergence where the storms have formed. The result has so far been incredible rainfall rates from these storms that have been nearly stationary. As of this writing the areas in the most persistent rainfall have seen over FIVE inches of rain in an hour, locally exceeding 200 year ARIs for primarily the 3-hour FFG. As the storms so far have shown no sign of weakening, and in fact have actually continued to intensify despite the dry air, expect locally significant and life-threatening flash flooding. The storms are over or very near I-95. Storm total rainfall amounts as of 0130Z/8:30pm EST with these storms are over 10 inches with these storms and counting. Much faster westward-moving training cells are moving through the Titusville and Cape Canaveral areas. Due to their faster movement, flash flooding associated with these cells is likely to be much more localized and less severe, but the threat for possible flash flooding remains here and into the Orlando area, where rainfall rates have been lower, but urbanization locally lowers the FFGs, making localized flooding possible. The ERO areas have been shrunk with the Slight now confined to just the Space, portions of the Treasure Coast, and portions of the Orlando Metro. Of course the main focus has been the line of storms mentioned above. Elsewhere rainfall rates have been largely under control, generally staying at under an inch per hour. Given the previous rain from throughout the day, the Slight is maintained in Orlando as localized flooding concerns are possible in any flood sensitive urban areas. Due to the aforementioned dry air, it appears likely that no significant rainfall can be expected much to the south of the persistent cell, so the ERO areas were trimmed entirely to the south, and left more broadly to the north where the rains continue this evening. Wegman Day 2 Valid 12Z Fri Nov 17 2023 - 12Z Sat Nov 18 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 3 Valid 12Z Sat Nov 18 2023 - 12Z Sun Nov 19 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8ZjCMqoz-SDXw-zqRV6_rxwRcJ-iJgpFHIA9VdDJxR3A= j7XckyeGFKHCUeA03cRcJWDW9QQW1EUFu4xFxng4GFAtDGo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8ZjCMqoz-SDXw-zqRV6_rxwRcJ-iJgpFHIA9VdDJxR3A= j7XckyeGFKHCUeA03cRcJWDW9QQW1EUFu4xFxng4dmY8l4E$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8ZjCMqoz-SDXw-zqRV6_rxwRcJ-iJgpFHIA9VdDJxR3A= j7XckyeGFKHCUeA03cRcJWDW9QQW1EUFu4xFxng46KlfIGc$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .