Severe Weather Poised to Strike Again

Last week's severe weather outbreak was largely a bust despite the system producing nearly 400 damaging wind reports, over 350 severe hail reports, and 40 tornado reports in six days.  Eight of these tornado reports were associated with an EF3 tornado that touched down in eastern Mississippi and traveled just over 68 miles into western Alabama, leaving one dead and nine injured.  However, most weather models overpredicted the amount of moisture that was present in front of this system, which led to a threat in reality that was less concerning than was once predicted.  If a more unstable air mass had been present, this system would have likely produced many more severe weather reports, including more long tracked, violent tornadoes.  The Storm Prediction Center noted this issue when describing their somewhat busted forecasts and stated that this tends to be a concern for the first early severe weather season system.

Well, here we go again, as another system approaches many of the same areas as last week's system.  This time the concern that the models will overpredict the amount of moisture present should be significantly lower.  This is due to the amount of moisture left behind by the last system as well as continued return flow from the Gulf of Mexico across most of the threat regions.  A dry line and stationary front today and tomorrow will remain nearly stationary until Wednesday when it begins to push east, reaching the east coast by Friday.


The largest threat at this point is expected to occur on Wednesday and Wednesday night.  The Storm Prediction Center has issued a Day 3 moderate risk for portions of central Oklahoma, southeast Kansas, and extreme southwest Missouri.  This is only the twelfth time the Storm Prediction Center has issued a Day 3 moderate risk since the first one was issued for a June 10, 2005 event.  Of the 12 events, four events resulted in the issuance of a Day 1 high risk.  These events resulted in varying reports of severe weather but all resulted in some reports.  The June 10, 2005 event recorded the least amount of severe weather but this also comes at a time when severe weather reports were not reported as frequently as today.  In this event, only 4 tornado reports resulted along with 55 wind damage reports and 59 severe hail reports. However, some events that prompted Day 3 moderate risks that were later upgraded to Day 1 high risks resulted in much more historic events, such as April 27, 2011 and April 14, 2012.

The risk on Wednesday does appear that it could result in all forms of severe weather, including the potential for strong tornadoes.  To the right is my threat outlines for Wednesday and Wednesday night defined by an area that has the potential for CAPE values above 1000 J/kg within the area outlined by the orange line, potential for convective type precipitation within the area outlined by the green line, bulk shear values greater than 40 knots within the area outlined by the brown line, 0-3 km helicity values greater than 300 meters squared per seconds squared within the area outlined by the red line, and 0-3 km EHI values greater than about 3 within the area outlined by the pink line.  All of this information was used for me to come up with my threat area to the right.

This threat area is very similar looking to the current Day 3 threat issued by the Storm Prediction Center, with a slight risk being portrayed in yellow and the moderate risk where tornadoes would be more likely being shown in red.  The Storm Prediction Center also has a threat area on Day 4 and this is shown below.  I have put together a tentative map of my threat area for this day as well, which will be Thursday and Thursday night.  This day should have fewer severe storms than the previous day due to lower CAPE values and weaker shear values.  However, the threat for an intense squall line to develop is one that could bring widespread damaging wind reports.  The threat for tornadoes will exist but Wednesday and Wednesday night should have a better chance of these.

Once again my threat looks similar to the current Day 4 threat where the Storm Prediction Center has outlined the 30% area of severe weather within 25 miles of a point.  I do not think they will introduce another Day 3 moderate risk tomorrow for Thursday and Thursday night, but I think the area I outlined in red will include a 30% probabilistic at this point.  If as the event gets closer the wind damage threat becomes more apparent or a greater threat of tornadoes appears to evolve than a moderate risk will likely be warranted at that time.

Stay tuned for further updates on this weeks developing severe storms situation!