Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 17 2023 01:14:57 AWUS01 KWNH 170114 FFGMPD FLZ000-170413- Mesoscale Precipitation Discussion 1176 NWS Weather Prediction Center College Park MD 814 PM EST Thu Nov 16 2023 Areas affected...Portions of the Space and Treasure Coasts of East Florida Concerning...Heavy rainfall...Flash flooding likely Valid 170113Z - 170413Z SUMMARY...Locally extreme rainfall rates to 5 inches per hour are ongoing south of Melbourne near Sebastian this evening. Flash flooding is likely. Westward moving training cells north of there through Titusville also pose a lesser flash flooding risk. DISCUSSION... 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 mb is pumping 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 potential instability the storms need to sustain themselves. 1,000 to 2,000 J/kg of MUCAPE are noted in SPC mesoanalysis just off the coast, which has increased 500 J/kg in just the last 3 hours. 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. They have been backbuilding towards the south and east based on recent radar imagery. As of this writing the areas in the most persistent rainfall have seen rates over FIVE inches of rain an hour, locally exceeding the 100 year Annual Recurrence Interval. As the storms so far have shown little sign of weakening, and in fact have actually continued to intensify despite the dry air, expect local flash flooding. The storms are over or very near I-95 near Sebastian. HRRR guidance on the evolution of these storms is likely too broad, as thus far the area of extreme rainfall rates associated with these cells have been very localized. Nonetheless the HRRR suggests these storms could persist another several hours in this region, remaining nearly stationary or slowly continuing to backbuild south and east. The duration of these storms is highly uncertain though, as they will continue to compete with the dry air aloft. Prior to and through the passage of the evident shortwave in water vapor imagery, it's likely the shortwave enhanced the lift locally, allowing the storms to form along the moisture gradient. Now that the interface of the shortwave is now well north and east of the storms, that forcing should be diminishing. This should eventually allow the dry air to overwhelm the storms, resulting in their weakening, but how quickly this occurs and when is highly uncertain as the aforementioned moisture convergence so far has been more than enough to sustain the storms. Wegman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6JMkMJagbXBEEEU8tRkfrM567FzgVqzEhedMTwYSJ00zkcTIGoN4mbRQwraf1z6ZN60M= 8x0je-U47QXbJdcuOk7OOeE$ for graphic product... ATTN...WFO...MLB... ATTN...RFC...SERFC...NWC... LAT...LON 29058072 27608022 27608062 28078105 28638122=20 28888118=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) .