Morning Convection Across the Midwest
While it may be winter, unseasonably warm conditions on February 19 were able to support convection across portions of the midwest and into southern Ontario. Convection began firing at multiple locations, including metropolitan St. Louis, Missouri; northeastern Indiana, and southeastern Illinois. To start with, let’s look at the 1500 UTC (9 AM CT, 10 AM ET) surface map as analyzed by NOAA’s Weather Prediction Center. Here, a weak frontal boundary stretches from Ohio southwesterly to a center of circulation in northeastern Kansas. Along and south of this boundary, conditions are quite moist for this time of year with dew points in the mid to upper 50s. There’s also evidence of a weak shortwave at 500 hPa over southern Illinois and western Kentucky that could be abetting any convection that develops (see here).
This can be a challenging part of the country for upper air observations as one of the nation’s larger radiosonde gaps is found between Lincoln, Illinois; Nashville, Tennessee; and Wilmington (suburban Cincinnati), Ohio. Still, looking at some of these soundings can tell us some things. The morning sounding from Nashville, for example, shows small amount of CAPE, which, when assisted by some weak upper-level dynamics, can cause some deeper convection to take place.
The GOES-19 mesoscale sector was active over the region, enabling a fine-scaled view of the evolution of these systems. We’ll start with the Day Cloud Phase Distinction RGB. This product is well-suited to identifying fast-developing cumulus which can quickly evolve into deep convection. The congested clouds transitioning from green to yellow are the cells to watch, as green represents glaciating clouds and yellow notes thick clouds with ice particles which are consistent with deep moist convection.
Similarly, the day convection product can help identify locations where convection is developing. Yellow spots indicate where strong updrafts are taking place, as this is where both cold cloud tops and small ice particle size (associated with young convection) are found. Here, we see that actively developing storms are taking place in northeastern Indiana, south-central Michigan, the Ontario peninsula, and the southern part of the Indiana/Illinois border.
Let’s take a closer look at the development of the cell on the Illinois/Indiana border. The following animation depicts both the day cloud phase distinction (top) and day convection (bottom) RGB products. The CIMSS LightningCast product has been overlaid on both RGB products. There is an existing area of convection on the western edge of the image, while the new cell can be seen developing in the middle of the animation. The first contours of lightning probability from LightningCast are seen at the same as the signs of convection (yellow and green in the top, yellow on the bottom) in the RGBs.
When AWIPS renders animations, the colorization can appear somewhat muted. Here’s a single frame from the above animation that better depects the colors as they are seen in AWIPS or SSEC RealEarth.
Additional convection is expected later in the day in this region as the first round moistened the environment and continued heating is expected to further destabilize the atmosphere.