NUCAPS comes in more unstable

AllSky LI is dropping over time...with the peak red color above being around -8.  Modified NUCAPS sounding came up with -11...whereas non-modified was -6.  CAPE also is more unstable in new sounding...whereas AllSky is in the mid 2000s, NUCAPS was mid 3000s...non-modified in the mid 1000s.

Bowing Segment moving toward Wright Co., MN

A bowing segment heading toward Wright Co., MN initially showed diminishing convective trends.  However, some drying in the wake of the line combined with strong wind speeds within the lowest tilts of the radar depicted some concern for severe wind gusts, and after a diminishing trend ProbSevere did begin to increase again.  Looking at the All Sky LAP CAPE, instability increased from ~960 J/kg at 1627z to ~1650 J/kg at 1828z, so the All Sky CAPE product showed some utility of assessing the downstream convective environment.

FGF cell developing into far northwest MPX area...moving into a little better CAPE environment

TOE showing southwest storm getting brighter

Flash extent density focused on that storm as well.  Prob severe coming up.  Had 50 dBZ to 48 kft and ~115 knot Delta V at storm top.

Mid-level moistening on AllSky PW products

In the wake of the storms, AllSky layered PW products showed the mid levels moistening...leading to the higher Total PW values.

All Sky LAP CAPE and convective trends

Thunderstorms continued to strengthen in the MPX CWA after 18z.  The All Sky LAP CAPE indicated instability building over Kandiyohi County as of 1728z (note some latency).  There is a line segement of tstms moving into this area, and a SVR has been issued as of 1821z for the SW part of the line as it moves into the region of higher instability.  Note, this development likely triggered along outflow from an earlier complex.  The SVR polygon was edged to the SW closer to the higher instability.



As of 1834z (not shown) the updrafts on the SW flank of the line continue to become dominant, and ProbSevere has increased to 76%.

AllSky TPW better feel for moisture in atmosphere

Noticed the AllSky TPW had a seemingly better handle on moisture over western MPX area than the more blotchy Merged TPW.   Looking at other instability parameters, the TT were in the mid 50s over western MPX, lifted index, K index upper 30s, CAPE mid 2000s.  Eastern storm following the gradient of the CAPE to the southeast.  AllSky has shown the CAPE increasing rapidly ahead of our storms.

Severe Threat over Minnesota This Afternoon

Ongoing complex of thunderstorms pushing into south central MN this hour.  Have a new set of thunderstorms forming in what AllSky is showing as a higher CAPE environment along the outflow pushing out from this complex.  ProbSevere has picked up on this cell as well (near Milan)...showing a Hail chance of 55% now and growing quickly.  Will monitor the downstream growth of both systems.

Today's Experimental Operations - Tuesday, June 4, 2019

Today's operations will be begin with their focus over the Twin Cities/Chanhassen (MPX) county warning area.  Severe storms have already developed and are approaching the Twin Cities area from the northwest.  The Storm Prediction Center current has a mesoscale discussion out for the area highlighting potential watch issuance within the next few hours with the main threat being damaging winds but large hail is also possible.


Other potential regions of operation include the low-country region of South Carolina, where there is currently a severe thunderstorm watch, and extreme west Texas into southern New Mexico.  We'll monitor the weather situations in these locations and adjust our operations area as needed.

Wild weather weekend

Severe weather abounded this Memorial Day weekend, punctuated by a strong tornado in Dayton, Ohio. Tornadoes were observed in 13 states over the three days, from Idaho to Pennsylvania and from Texas to Minnesota. The Dayton storm emerged on the south end of a cluster of severe storms entering Ohio from Indiana (Figure 1), with nothing in its way from ingesting air parcels in an excellent environment (~1800 J/kg MLCAPE, ~55 kts eff. bulk shear, ~300 J/kg 0-1km SRH, ~40 kts 1-3km mean wind). This storm rapidly increased in ProbTor and produced its first tornado at 02:35 UTC, right after ProbTor exceeded 85%. The storm exceeded 90% ProbTor for almost an hour (see Figure 2), during which time the Dayton area suffered extensive damage. A tornado emergency was also issued for Dayton by the NWS at around 03:00 UTC. See the archived time series of ProbSevere products and predictors here and here (the storm merged with a storm to its north, prompting a change in ID).

Fig. 1: A cluster of storms with ProbSevere objects, MRMS MergedReflectivity, and NWS severe weather warnings. The Dayton storm is highlighted.

Fig. 2: Time series of the ProbSevere products in relation to severe LSRs and NWS severe weather warnings. 

A handy feature on the ProbSevere webpage is the "ProbSevere Accumulation" tab, which allows users to get a quick-look at the severe weather for a day and check out ProbSevere's performance. Once clicking the tab at the top, users can set the date using the UI on the left. Each day is considered a "convective day", starting at 12Z and going to 12Z the next day. For example, 2019-05-26 12:00 UTC is the start time and includes reports, NWS warnings, and ProbSevere objects from that time until 2019-05-27 11:59 UTC.

You can see the extent of the storms for the convective days 05-25, 05-26, and 05-27 in Figures 3 through 5. The green, blue, and red circles are preliminary LSRs for large hail, severe wind, and tornadoes, respectively. The orange and red polygons are NWS severe thunderstorm and tornado warnings, respectively. The white and pink boxes are centroids for ProbSevere objects at each valid time (every 2 min), colored by the probability of any severe value. In this way, a user or researcher can quickly see which areas ProbSevere 'hit' on, 'missed' on, or had 'false alarms' at the 50% threshold.

Fig. 3: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-25.

Fig. 4: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-26.

Fig. 5: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-27.

April and May have seen above average tornado activity nationwide, with the U.S. inflation adjusted number of tornadoes at 794 through yesterday, at about the 90th percentile for this time of year (Figure 6).

Figure 6: U.S. inflation adjusted cumulative annual distribution of tornadoes.