Variability in CI

It is interesting to note the variability along the CU field from east-central IA into northern IL. This CU field developed into TSRA the next satellite scan in the regions all along the line. The variability in CI ranged from 27 to 70 percent.

-JB

Nearcast storm feed.

With this post I just wanted to showcase off the Nearcast model’s difference in Theta-E layers as a large area of instability is feeding directly into the lonely storm over Denver. With no slowdown of the instability feeding this storm, it will probably continue into the late early evening hours.

Grant H.

ProbSevere lining up with experimental warnings

High ProbSevere values (> 75%) are evident on a number of storms along the cold front/stationary boundary near the IA/WI/IL nexus. These storms largely had moderate-degree satellite growth rates in an environment characterized by 2400 J/kg of MUCAPE and 50 kts of effective shear. Large MESH also became apparent, contributing to the high probabilities of severe. The moderate satellite growth rates occurred during a 30-min scan gap from GOES-East. The growth rates likely would have been labeled "strong" if the temporal resolution was better. Despite this, lead times to first NWS warnings were between 0 and 16 minutes on these storms, measured from a ProbSevere value of 50%.

These experimental warnings from the HWT forecasters in Davenport, IA, corresponded well with the storms with large ProbSevere values, increasing user confidence. Multiple hail reports have been recorded, including 2" diameter hail.

-Cintineo

Flash Extent Density and Storm Structure

Overlaid here is Flash Extent Density (FED; shaded pink and blue boxes) and Reflectivity at -10C at 22:11 UTC.  The lightning information is highlighting where active charge separation is ongoing within the storm, and lightning is occurring. Notice how the FED extends outside of the reflectivity cores within the two storms, highlighting how lightning propagation can and does occur outside where it is actively raining, posing a threat to those caught outside.



NLDN information has been added to the image above from the same time at 22:11 UTC.  The NLDN is represented my the minus signs within the image.  Note the difference in spatial information of lightning that the PGLM provides over traditionally used NLDN cloud to ground points.

Four minutes later at 22:15 UTC, the NLDN reported a lightning strike that occurs outside of the precipitation of the storm (white circle, below).

Convective Development in Iowa

Forecasters are focusing in on two areas this afternoon, one being in the Cheyenne CWA, and the other across Davenport, IA. Convection was already developing in the Cheyenne CWA by the time forecasters got on their shift, so focus quickly shifted to the other Experimental products. However, convection developed later over the Davenport CWA, which the CI product picked up on, but do to the 30 minute full disk scan at 2045 UTC, much of the convection was unfortunately missed. A benefit of GOES-R is the increased temporal resolution which will eliminate these large time gaps between satellite images. Below are two time stamps of the CI product (2045 UTC and 2115 UTC) along with two MRMS images of -10 C reflectivity (the reflectivity which the GOES-R CI product is validated against).

At 2045 UTC, the CI product is forecasting 50-60 percent probabilities of convection developing along a boundary sagging south into Iowa. 15 minutes later at 2100 UTC, the first 35 dBZ radar echoes were seen in the reflectivity data. 2045 UTC is a full disk scan for GOES, so the next available satellite scan was at 2115 UTC. In the meantime convection continued to develop which the CI product missed because of the 30 minute scan, but did capture another area of 60 percent development which continued into a storm that was severe thunderstorm warned. Lead time was minimal of ~3 minutes due to the large 30 minute gap.

GOES-R CI at 2045 UTC

2100 UTC MRMS -10 C reflectivity

2115 UTC GOES-R CI product

2118 UTC MRMS -10 C reflectivity

Western Iowa storms

In western IA (outside of our current operations), storms exhibited strong satellite growth rates by 20:45 UTC. Figure 1 shows high ProbSevere probabilities (70-85%) at 21:08 UTC. The storm to the southwest had >70% probability of severe as early as 20:48 UTC. The NWS issued a warning at 21:19 UTC (31 min lead time). The northeast storm had 14 min lead time (from the 70% threshold) to an NWS warning. These storms in western Iowa nicely illustrate how satellite growth rate information can increase lead time to severe weather warnings. Each storm has had at least one 1" hail report, via the SHAVE project.

Figure 1: ProbSevere contours of storms in western Iowa. These contours have strong probabilities of severe (70-85%).

Figure 2: Initial NWS warnings.

-Cintineo

NearCast Supports Weakening

The gradient of theta-e difference remains in eastern WY. Storms have developed and moved east across this convective instability gradient producing marginally severe hail. Throughout the day the NearCast model indicated the convective instability weakens across the NEb panhandle. Below is an email with two supercell moving across the convective instability axis. The lead supercell is currently weakening and also moving out of the instability axis.

First impressions with the new tracking tool.

First impressions with the new tracking features. graphs next to the tracking bar in the meteogram may need to be more editable. In this case were were able to zoom out of the Y axis allowing dBZ to show up as a more usable function. However it still is lacking some standardization of axis that is more common from other programs functions like Excel and Powerpoint graphs. Perhaps finding a way to automatically load a standardized graph  when certain meteorological fields show up. (dBZ, VIL, CC, etc..)

Also of note. Shortly after zooming out on the axis…. other panes  that were on screen where not accessible for a very long time . Probably 5 to 10 minutes while writing this blog.

Grant H.

ProbSevere on the high plains

Storms have developed nicely over southeast WY and the Denver, CO region. In Denver, a storm had a strong glaciation rate but a weak normalized vertical growth rate initially (figure 1). As the MESH increased to 0.89 in., the probability of severe increased to 53%. A scan later, the storm exhibited moderate vertical growth (from satellite), and the probability jumped to 71%.  This storm and the storm to its southwest were warned by the NWS (figure 2) almost simultaneously with the jump to 71% probability of severe. So though lead time isn't substantial in this case, ProbSevere could help with forecasters' confidence during warning operations.

Figure 1: Storms near Denver, CO

Figure 2: NWS warning on two storms near Denver.

In Wyoming, a storm that was over 120km from any radar, had strong and moderate satellite growth rates and had 52% probability of severe (figure 3) about 3-4 minutes before an NWS warning was issued (figure 4). In a low CAPE environment, 50% is usually significant for ProbSevere. Again, ProbSevere may be able to aid forecaster confidence during the warning operations process.

Figure 3: Storm in southeast Wyoming

Figure 4: NWS warning at 3:53pm

-Cintineo

LAPS Theta-e vs. NearCast Theta-e Difference

For today, my area of focus is in the DVN CWA. I began by looking at some of the satellite imagery and associated products, such as CI and OT detection. It’s still a bit too early for the OT product to be useful and the CI product is just now beginning to hone in on the developing CU field across the region. In the first image below, I’ve scalloped the region where the CU field has been evidently increasing in coverage and vertical growth. The CI product doesn’t show anything above the 40% range just yet but it still is a good way to bring attention to this area for possible initiation as conditions become increasingly favorable for development. There is a location just south of the area I’ve outlined that shows a 70% chance for CI so that’ll be something to watch as well.

In the next image (below), I loaded the CONUS LAPS theta-e analysis (image) along with wind and METARs/station plots (the 800×800 domain is not available for this region today). Again, the area of interest is across the northern border of the DVN CWA. Except for the bulls eyes that appear where there are seemingly bad obs being ingested (when toggling over to the dewpoint analysis, these locations are evident), this has been a good situational awareness tool as well as a good product to put together a mesoscale analysis.



Comparing the analysis above with the theta-e difference product below, much of the DVN CWA is under an area of convective instability. Unfortunately, the aforementioned scalloped area of interest in the northern half of the CWA is blacked out so I’ve had to infer and fill in where a lack of data exists. It would appear that a gradient exists right through this area, which lines up with all previously analyzed parameters and products hinting that this is the area to watch over the next 0-2 hours.



~Linda