Storm Prediction Center Mesoscale Discussion 199
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Mesoscale Discussion 199 | |
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Mesoscale Discussion 0199 NWS Storm Prediction Center Norman OK 1007 AM CDT Sat Mar 15 2025 Areas affected...Eastern Louisiana and much of Mississippi Concerning...Severe potential...Tornado Watch likely Valid 151507Z - 151700Z Probability of Watch Issuance...95 percent SUMMARY...A Particularly Dangerous Situation Tornado Watch will be issued soon. A tornado outbreak with multiple intense to violent long-track tornadoes is likely. DISCUSSION...Morning observational data continues to support a likely tornado outbreak today across parts of eastern Louisiana and Mississippi. 12Z RAOBS from LCH and LIX indicate rich low-level moisture featuring a mean mixing ratio of 14 to 15 beneath a steep EML with mid-level lapse rates of 8 to nearly 9 C/km. This thermodynamic profile, combined with broken cloud cover across Louisiana and southern Mississippi suggest substantial heating will occur and strong instability will be present for much of the day today. The EML will play a critical role in the storm mode today. Discrete supercells are anticipated given the EML which will suppress more widespread convection and also provide enough mid-level dry air for potentially multiple well-organized supercells in close proximity through the day. In addition, 12Z RAOB data along the Gulf Coast is consistent with the data observed the morning of historical tornado outbreaks across Mississippi and Alabama. Strong shear is already present across Louisiana and Mississippi this morning with effective shear 40 to 60 knots at the LIX/LCH/JAN 12Z RAOBs. However, shear will increase further through the morning as mid-level flow strengthens with the mid-level jet streak overspreading more of the warm sector and with secondary surface cyclogenesis in the mid-Mississippi Valley. Early evidence of this secondary low-pressure center has already been observed with a sub-995mb surface low analyzed northwest of Little Rock, Arkansas at 15Z. This surface low will continue to deepen and consolidate through the day which will keep flow backed across the warm sector and result in further strengthening of the already strong low-level jet. By mid-afternoon, a low-level jet of 65 to 70 knots is forecast with corresponding 0-1km SRH of 300 to 500 m2/s2. The presence of nearly pure streamwise vorticity in the lowest 1km will create an environment extremely conducive to the stretching of the ambient low-level vorticity. Confluence bands across Louisiana this morning likely represent the initial supercell initiation zone for the storms of greatest concern this afternoon. Multiple bands of supercells are possible. Once mature supercells develop in the environment south of the messier convection, there should be very little to interrupt their longevity through the afternoon. Given the aforementioned factors, many discrete supercells are expected in an environment which is extremely conducive to tornadic activity. Therefore, a tornado outbreak appears imminent with the potential for multiple, intense to violent long track tornadoes from mid-day through this evening across eastern Louisiana and much of Mississippi. A Particularly Dangerous Situation Tornado Watch will be issued soon to address this threat. ..Bentley/Gleason.. 03/15/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BMX...HUN...MOB...MEG...JAN...LIX...LCH...SHV... LAT...LON 33289093 33959023 34478950 34728889 34648832 34558813 33698827 31718846 31238894 30768995 30779104 31009190 31559220 32039197 32649162 33289093 |
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2025-03-15 16:01:02