The balmy airmass across much of the eastern U.S. provided the fuel for severe storms across the Great Lakes and Mid-Atlantic regions for a while now.ProbSevere v4 (PSv4) uses spatial AI methods and MRMS, lightning, and HRRR environmental information to predict the probability of severe weather in the next 45... Read More
A shortwave trough with moderate low-level flow spawned storms across the northern U.S. Below is the convective outlook discussion from the SPC at 16:30 UTC. ...Northern High Plains into the northern Plains... Recent satellite imagery shows a well-defined shortwave trough moving eastward across southern Saskatchewan and western MT/eastern ID. A... Read More
In this post we see how ProbSevere v4 performs with Southeast microbursts, which are notoriously difficult. In parts of the Carolina, effective shear was a bit higher (20-30 kt), producing cell clusters. PSv4 probabilities and motion progressed well with these. Elsewhere, especially from Louisiana to Georgia, the shear and mean... Read More
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
