Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 05 2024 17:45:11 AWUS01 KWNH 051745 FFGMPD SCZ000-FLZ000-GAZ000-052300- Mesoscale Precipitation Discussion 0811 NWS Weather Prediction Center College Park MD 144 PM EDT Mon Aug 05 2024 Areas affected...Far Northern FL through the Coastal Plains of GA and SC Concerning...Heavy rainfall...Flash flooding likely Valid 051743Z - 052300Z Summary...Continued heavy rain ahead of Tropical Storm Debby will expand slowly northward from northern Florida into northeast South Carolina. Rainfall rates of 2-3"/hr will be common, which could produce 3-6" of rain with locally higher amounts to near 8" possible. Flash flooding is likely. Discussion...The regional radar mosaic is quite impressive this afternoon surrounding Tropical Storm Debby. The center of T.S. Debby is clearly evident near Live Oak, FL, and is lifting slowly northeast around 8mph according to the 11am NHC advisory. Along and ahead of this center, rainfall has gradually expanded and intensified as far north as the Horry County, SC coast, with widespread 0.5-1"/hr radar-estimated rain rates spreading northward, with embedded convective cells of 2"/hr. The central dense overcast (CDO) is clearly evident E/NE of the center, and within this region persistent rainfall rates nearing 3"/hr are being measured which has resulted in a recent Flash Flood Emergency where more than 10 inches of rain has already fallen. These intense and efficient rain rates will continue into the evening as the environment remains exceptionally favorable noted by a record PW measured on the 12Z U/A sounding out of KJAX of 2.85 inches within a deep warm cloud depth of above 17,000 ft. As T.S. Debby continues to pivot slowly northeast this afternoon, it is likely that rainfall will continue to spread along the coastal plain of Georgia and South Carolina where an impressive theta-e ridge will advect northwestward. This theta-e surge will occur thanks to cyclonic flow around Debby reaching 40-50 kts to converge onshore into a surface trough analyzed by WPC. The accompanying isentropic lift of this flow will additionally enhance ascent and increase MLCAPE onshore, resulting in more widespread heavy rain rates which have a 20-25% of exceeding 2"/hr according to the HREF neighborhood probabilities. With Corfidi vectors aligned exactly anti-parallel to the mean wind, training of these rates will become increasingly common, resulting in repeating rounds of intense rainfall from southeast GA to northeast SC. At the same time, the CDO will gradually pivot northeast as well, interacting with the surface trough and lifting theta-e ridge to even more impressively enhance rain rates. The heaviest rainfall is likely where this CDO drifts overhead due to the nearly continuous 2-3"/hr rain rates embedded within it. HREF neighborhood probabilities across this region reach 60-90% for 3" and as high as 60% for 5" in the next 6 hours, and it is possible some locations that experience the CDO could accumulate up to 8" of rainfall into this evening as reflected by both the HREF and REFS PMM. This excessive rain will likely result in widespread flash flooding, some of which could be significant to locally catastrophic. The most likely areas to receive catastrophic flash flooding will be underneath the CDO, but as persistent heavy rain spreads onshore into the coastal plains of GA and SC, the significant flash flood risk will increase in these areas as well, especially over any urban centers. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-hOU_B7of1o-9pOElmK0Dv0aIyUt6DRDNefsB1HANiS63F4ay-qLsM7MBEKNa7gVambz= Hur77-ZVWjHsc98a7XDpC1Q$ for graphic product... ATTN...WFO...CAE...CHS...FFC...ILM...JAX...TAE... ATTN...RFC...SERFC...NWC... LAT...LON 33927995 33847927 33597894 33167914 32837962=20 32198046 31638087 30708122 30108125 29908184=20 29878242 30048293 30388350 30698395 31078421=20 31598417 32458280 33338138=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .