Forecasting Recap: ArkLaTex Severe Weather Event. April 13th, 2019.

Surface Analysis for 18z showing the northward movement of the warm front and the progression of the east moving cold front into east Texas and Louisiana.

 If you haven't read my forecast for this day, you can click here.

How Did The Forecast Do? What Happened Throughout The Day?

As I was over 1,200 miles away from the system, I was arm chair forecasting and observing from home. The strong speed and directional shear, and high dew points went exactly as forecast: very intense. Storm Relative Helicities (both 0-1 km and 0-3 km) exceeded 250 m2/s2, suggesting strong rotation in any storm with a strong updraft. This was a surprise to no one, though; given the synoptic set up. The warm front rose north early in the day (you can check the 18z surface analysis above) and reached extreme north Louisiana by 21z. This increased the size of the warm sector, in tandem with diurnal heating, allowed for instability to build quickly as whatever small amount of CIN (capping) was eroded. Storms, due to the prefrontal trough, an advancing cold front, a completely uncapped warm sector, and extremely low LFCs (requiring little forcing for storms to form) began to erupt early and continued to fire into the afternoon. 

Unfortunately, there were people killed due to the flooding and high winds associated with this widespread event. 5

The day starting off early with a confirmed tornado located near Franklin, Texas in the morning (around 11am CST). Many believed that this would be a sign of things to come. 465

Not many discrete cells as of 21z.

From around 21z on, the majority of discrete storms that formed in eastern Texas and Louisiana quickly became congealed, or linear. As a whole, storm mode became very messy, and it became a largely wind and high precipitation event in Louisiana.

Lack of discrete cells notwithstanding, QLCS (embedded) tornadoes were still a threat among the linear convection. This was the case with at least one confirmed tornado hitting the town of Vicksburg, Mississippi as part of at least one tornado embedded in a QLCS. 

There was also a later in the night scare, as another embedded-in-a-squall-line tornado was on a collision path with MSU Campus. The good news was no injuries were reported. Nocturnal tornado reports as part of the eastward moving QLCS would continue throughout the night, with Monroe County, MS being hit particularly hard.

Overall, I do wish I had considered the faster eastward track into western Mississippi and Alabama later in the day (I did not think they'd reach that area until well into the night. They arrived in those states faster than I thought). The abundance of messy storms as a result of upscale growth was confirmed. The lack of discrete tornadoes was a possibility that I mentioned in the concerns section of my forecast; largely depending on storm mode and warm sector forcing, but truthfully, I thought the parameters in place would have meant more discrete tornadoes ahead of the strongest forcing. Thankfully, that did not occur.

I also underestimated just now frequent and intense the embedded, nocturnal, tornadoes would be once they tracked into Mississippi.The hodographs had hinted at an environment prone to rotating storms, but I was not expecting the number and intensity of some of the tornado reports.

As a side note, I do plan on making future forecasts more in-depth. I decided to start a blog late last night on a whim, so there's a bit of a learning curve. 

The (Nearly) Final Storm Reports

Here is the preliminary total of storm reports that include tornado, hail, and wind damage reports. Total reports should increase in the coming days as damage surveys are conducted. The night before, and morning of, suggested that tornadic parameters were very high and it was quite likely that several tornadoes - some of which could be violent and long tracked - would occur across the ArkLaTex and western Mississippi. As I write this recap, I'm sure most people closely monitoring this event were expecting a higher confirmed amount of tornadoes on the day, and thankfully, that was not the case. This event ended up being a larger localized flooding threat in Louisiana than a tornado threat.

How Did My Target Area Do?

Isolated convection quickly congealing and becoming linear prevented supercells from staying discrete and becoming strong tornado producers. An example of broad rotation just north of the target area was observed around 2 pm CST. This was not surprising, considering the supercell/tornado parameters discussed in the previous day's forecast, but no tornadoes were produced in the immediate area. To give you an idea of the volatility of the atmosphere, here's a look at a box and whisker plot showing all tornado ingredients at or exceeding strong tornado parameters in the area.

I would not have seen a tornado had I been chasing that day; considering the chosen target area. I can say that I may have pushed back to the north and east to stay ahead of the upscale growth, but there's no way of confirming that I would have been able to cover that much ground in a very messy, very rainy day. The roads may have been subjected to flooding as well. There would have been a chance at great lightning opportunities outside of the main rain cores, so I may have tried my luck there. I don't like these types of grungy, low visibility, fast moving storms, so I likely would have stopped early and gone to watch the NBA playoffs.

Until the next event...