Significant Weather Events

May 9-10, 2019 Severe Weather

Outflow from showers and thunderstorms earlier in the day and a slowly moving cold front produced several rounds of severe thunderstorms through the evening hours into the overnight hours of May 9th and 10th. Several supercell thunderstorms produced significant hail in excess of two inches across Southeast Texas and Southwest Louisiana. A squall line then moved through the region during the overnight hours and produced significant straight line winds across Southeast Texas.

Meteorological Overview

Hail Swaths

Jefferson County Macroburst

Convection ongoing across Central Louisiana during the morning and afternoon hours of 9 May slowly progressed southward through the day. The outflow on the western edge of these storms combined with a southward moving cold front across East Texas resulted in an area of enhanced forcing for ascent across portions of Southeast Texas and southwest Louisiana. As a result, additional deep moist convection develop across the region during the late evening hours of 9 May.

The 10 May 00Z KLCH sounding sampled the outflow with a cooler saturated temperature profile and easterly winds from the surface up to around 850 hPa. Above 850 hPa, moderate to strong instability was present with around 2500 J/kg CAPE. This instability in conjunction with wind shear of 45 to 60 knots would support the potential for organized deep convection including supercells. Unidirectional wind vectors generally out of the southwest above 850 hPa resulted in a relatively straight hodograph indicating the potential for splitting supercells. Left-split supercells have been previously associated with significant (greater than 2 inches) hail events. The first supercell of the event was a left split which produced significant hail across northern portions of Jasper County.

Further to the west near Houston, the southwesterly winds aloft being aligned parallel to the surface cold front promoted the upscale growth of cold pools from the initial convection developing along the front. This resulted in the initial storms congealing into a line which accelerated eastward. Ahead of the line, several supercells developed during the late evening hours and produced additional significant hail across portions of Southeast Texas and Southwest Louisiana. As the line moved into Jefferson County, a portion of the line bowed out and produced winds ranging from 60 to 90 MPH over a distance of 23 miles.

NOTE: These hail maps are based off of radar estimates of hail size and will likely not represent the actual size of hail that fell at a specific location.

South of Fannett, an area of a strong thunderstorms began bowing out leading to an increase in wind speeds. Tree damage began to become increasingly evident in a width extending from around Boondocks Road south of Fannett to just north of FM 365. More severe tree damage and some minor outbuilding damage was noted in the community of La Belle and extending eastward along Garner Road where the bow velocities appeared at their maximum of 90-95 MPH. Tree damage continued to be noted eastward into parts of Port Arthur, Groves and Nederland as the bow echo continued to fan outward. In this area, wind was estimated to be between around 60-80 MPH as the bow echo moved through. The Jack-Brooks Regional Airport ASOS and a personal weather station in Groves both measured 60 MPH wind gusts on the edge of the macroburst.

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