EWP Blog

After a brief look at guidance for convection chances in LWX today, it isn’t looking too great. There are some surface features with the latest analysis showing a trough stretching from central NJ down to central VA. A cold front is stretching through the entire country from north of Vermont to southern Mississippi. 17z GOES-R products shows the CAPE to the south in AKQ’s CWA as well as the highest LI/K index and PW values. Looking at the latest satellite imagery shows skies clearing after 16z over the CWA and cumulus fields developing. It looks like the latest satellite CAPE “may” be creeping west with the clearing and some storms showing some CI potential but nothing higher than 50-60% so far. RAP guidance doesn’t have the cold front moving through the region until after 21-22z. It also shows convective indices decreasing after that.

Summary? If we get any storms it will likely be before 22-23z moving west to east along the front. I don’t think the instability/shear is strong enough to get any significant initiation along the pre-frontal trough. I have highest confidence that areas to the south will get convection with the trough and/or the cold front.

I am watching ongoing thunderstorms move west through CWA MLB. Radar indicate cells that could contain small hail, below severe limits. Severe Prob indicates low percentages of turning severe. However, when sampling this data the north vert growth rate indicators read N/A. Glaciation rate also read N/A. Is this data missing? The problem with using N/A is that it is inconsistent with the weak/medium/strong qualitative descriptors. You can see Severe Prob using proper qualitative descriptors starting in the 1645z period, but as we progress toward 1745z those qualitative descriptors are gone.

UFFSU

New week, new participants, and a very different convective setup compared to last week. Today our forecasters were exposed to all that the EWP has to offer while operating in Wilmington, OH (ILN), Louisville, KY (LMK) and Houston, TX (HGX) ahead of a cold front that spanned from southern Michigan into central Texas. Forecasters quickly spun up on utilizing ProbSevere as a quick diagnostic tool to prioritize which storms to interrogate first. Forecasters were able to establish their first impressions, build procedures, and ask questions on the entire suite of products thrown at them. The established large squall line that dominated most of the country, while not helpful from the CI perspective, gave forecasters the ability to put the various diagnostic tools to work and compare outputs between mature and developing convection.

Overall, another “Day 1” in the books, here’s hoping for some interesting cases this week (fingers crossed and prayers needed).

-Darrel Kingfield, CIMMS/NSSL Research Associate & Week 2 EWP Coordinator

The first day of the EWP has been pretty intense but very interesting. I focused on a couple of storms in Texas: the first just west of Houston died pretty quickly but the second, north-west of New Orleans, proved more interesting. One of my favourite products so far is ProbSevere but I’ve found that it can be inconsistent with the polygons and probabilities.

At 21:00Z (below) there’s a 55% probability polygon highlighted in a high 0.5 Reflectivity area. To the northeast of this is a 5% polygon shown.By 21:20Z(below) these two polygons have merged with an 82% probability. The 0.5 reflectivity does not back this up, neither do the dangerous thunderstorm alert tracks.

Twenty minutes after at 21:40Z(below) the polygon has split again: 65% to the south and 5% in the north.It is proposed that this may be due to the thresholds used to create the polygons and the proximity of polygons to each other (i.e. polygons cannot appear to overlap). This is also just one case study so further study is required!

Minnie

The three thunderstorm alerts (Thunderstorm, Significant, and Dangerous) are nice to look at, but don’t add much value to the warning process because the polygons change every few minutes.

The East and WEST ENI DTA 10 min Motion Projections are nice references, but aren’t needed for warning purposes.

The East and West ENI DTA Rates are very useful for tracking the lightning trends in thunderstorms.  However, the algorithms “jump around” too much in lines of storms, splitting storms, and merging storms.  This makes it difficult to follow these algorithms at these times.

The East and West ENI DTA Cell Polygons seem too small given the size(s) of the storms.  This leads to smaller East and West ENI DTA Cell Flash Rates than is realistic.  Plus, these algorithms “jump around” too much in lines of storms, splitting storms, and merging storms.  This makes it difficult to follow these algorithms at these times.

The 1 km ENI Total Lightning Grid is very messy and is hard to use for warning purposes.  The 3 km grid seems to be the most useful.  5 km and higher seems to “wash out” the details of the storms.  This is using the 5-minute data, that is more likely to capture the current lightning trends.

The ENI Total Lightning Plots show the lightning as points (where the strikes/flashes/pulses occurred) and as a total count for each in the corner of the screen.  It would be nice to have the capability to turn the “points” off, but leave the count on.

5-minute data seems to be the most useful for the various lightning algorithms.  With 1-minute data it’s easy to miss trends.  With 10 and 15 minute data, they don’t update fast enough for rapidly evolving storms.

Champion

In this example there are way too many DTAs issued. As a forecaster, this many polygons over the same area would likely not provide useful information.

It appears this is a result of the ENTLN cell track algorithm grouping then ungrouping then grouping cells, which leads to new DTAs (which last for 45 min) for what was really the same cell.

Ertel

Currently, lightning is not considered for special marine warnings. However, lightning on the open waters can be deadly to boaters.

Here is an example (from the Texas coastline) of  5 minute cloud-to-ground lightning from the ENI Total Lightning Grid density at 5 km resolution:

With the addition of this data set into AWIPS2, the special marine warning criteria could be modified to use the density of cloud-to-ground lighting.  In the end, this will better meet the National Weather Service’s mission to protect life and property with regard to marine interests.

Polarimetric Researcher

While this is not the best example I have ever seen, the lightning data did a pretty good job of capturing the storm split and keying in on the stronger more dominant right mover.

Ertel

Broadcast meteorologists operate under a number of constraints in developing severe weather situations. As a broadcast met forecasts in real time, products that display easy to understand forecast information are more likely to be used and incorporated into breaking severe weather coverage. Prob Severe as CI Probability are elements that can be easily incorporated to on-air analysis, as they guide the broadcast meteorologist and the conversation he or she has with the viewing public.

UFFSU