Multiple MCSs were riding a ridge of high theta-e air over the middle of the U.S. Over 900 wind reports were recorded from South Dakota to South Carolina, with the highest concentration from Illinois to West Virginia. Multiple tornadoes were recorded, including an EF2 tornado in the southwest Chicago suburbs.While... Read More
Uncertainty is the name of the game this time of summer!From the SPC 1300Z outlook:...Synopsis... Another highly uncertain and complex forecast with mesoscale convective dependencies apparent this forecast update. Water-vapor imagery implies a belt of west-northwest mid to high-level flow extending across the northern High Plains east through much of... Read More
Momentum from northwest flow overlaid rich moisture in the upper Midwest and western Ohio valley spawned multiple clusters of intense storms, including supercells. Several tornadoes touched down in Wisconsin and Chicagoland, including the EF3 Menasha, Wisconsin tornado. Storms later congealed into bowing segments in Indiana and Kentucky.ProbSevere v4, the image-based... Read More
A cold front swept into New England on July 16, forcing severe “thunderstorms” in a low-CAPE environment. Thunderstorms is in quotations because many areas experiencing wind damage had no lightning. Most storms had lightning activity of 0 or 1 flash/minute. In fact, I only found 2 storms with more than... Read More
A mesoscale convective system (MCS) traversed the state of Alabama producing at least 200 damaging wind reports.Here is the SPC outlook discussion for this region. Interestingly, the western threat (in MO/AR) didn’t materialize nearly to the extent of the MCS in Alabama. The MCS was characterized by lots of CAPE... Read More
Numerous storms formed in the Pacific Northwest under dry microburst conditions, with relatively high CAPE for this region (500-1300 J/kg). One area of convection in southwest Idaho was moving northwestward. The ProbSevere v4 model tracked it very well with high probabilities before wind gust reports of 60-72 mph. It’s unclear... Read More
Moderate shear and moderate CAPE ahead of a shortwave trough produced numerous storm clusters in the Mid-Atlantic states. ProbSevere v4 captured the severe portions of these clusters fairly well (see below). There were some missed wind reports, but higher probabilities generally corresponded with NWS severe thunderstorm warnings quite well. In... Read More
LigthningCast v2 (LCv2) incorporates MRMS Reflectivity -10oC as a predictor alongside the GOES-R ABI predictors of LightningCast v1 (LCv1). Overall, we’ve found that LCv2 markedly outperforms LCv1. Below is an example in Oklahoma and Kansas where thick cirrus is obstructing the ABI’s view of developing convection underneath. LCv2 (on the... Read More
A number of convective clusters formed across a moist and moderately sheared airmass on May 23 and 24. Here are a few examples of ProbSevere v4 output. Please note that reports are valid for the 45 minutes after the image time. In Louisiana, PSv4 initially did an excellent job predicting... Read More
As noted in the SPC discussion, destabilization ahead of a shortwave in the Ohio Valley spawned prolific downburst-producing storms, in an environment characterized by 20-30 kt of shear and strong low-level lapse rates....Ohio Valley into the Mid-Atlantic and Southern New England... On the southern fringe of upper troughing over eastern... Read More
