SPC Mesoscale Discussion: Tornado Watch 419…

SUMMARY…A tornado threat remains possible through 11-12Z across southeast Louisiana into southern Mississippi with discrete storms, ahead of the primary line of storms. Meanwhile, the eastward-moving line of storms will continue through an environment conducive for damaging winds and a tornado threat. A new tornado watch will be needed by 11Z across central and southern Alabama and part of the western Florida Panhandle, as the air mass downstream destabilizes, supporting severe storms.

DISCUSSION…Trends in mosaic radar imagery showed a quasi-linear band of storms moving steadily eastward at 30-35 kt across MS and southeast LA into the northwest Gulf of Mexico, while discrete storms continued to develop ahead of the line from the Gulf into southeast LA/MS. These discrete storms were tracking to the north and north-northeast within an environment that is sufficiently buoyant and becoming more strongly sheared, given strengthening deep-layer wind fields and large hodographs. Individual radar imagery ahead of the line of storms indicated several of the discrete storms already have supercell structure from off the LA coast through southeast LA to southeast MS. A tornado threat will exist with these storms prior to them being absorbed/overtaken by the eastward-moving line of storms. Meanwhile, the QLCS should maintain its structure with eastward movement this morning, as it advances through the rest of WW 419 and at least through parts of central and southern AL and the western FL Panhandle. This will be due to the effective bulk shear vectors being oriented generally front parallel and forcing for ascent attendant to a lead shortwave trough moving across the central Gulf coast states toward the southern Appalachians this morning. Given the above mentioned increase in hodograph curvature and strengthening wind fields with eastward extent, damaging winds will remain possible with the QLCS, and a tornado threat with any embedded supercells or line vortices.

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