Line Formation with CI Prob

CI Prob continues to handle the developing line heading into western SJT cwa.  Visible satellite hints at outflow and developing clouds, but CI Prob helps confirm new storm initiations.  The 1930z 4 panel view shows the higher probability of thunderstorms developing along a line.

The larger view of the radar helps us verify the lengthening of the line into MAF cwa. These storms continue to move slowly SE. It should also be noted CI Prob is also indicating thunderstorm development ahead of the current line.  This area of convection will be contained in central SJT cwa. Will continue to monitor any possible development to see how CI Prob verifies in cloud/cirrus setting.

UFFSU

Experimental warning in SW TX

A caveat of MRMS products that the forecasters have been reminded of today is that MESH may be less accurate in single-radar coverage areas, far from the radar. This is the case where we're operating today, in parts of San Angelo's and San Antonio's CWAs. Figure 1 shows the CONUS NEXRAD Coverage. We can see that for the storm in Figure 2, the lowest level of the radar beam is about 10,000 ft. If the MESH is artificially high, the probability of severe will be artificially high.

Figure 1: NEXRAD Coverage Below 10,000 ft AGL. See the sparse radar coverage in southwest Texas.

With that said, this storm in Figure 2 is still looking quite healthy. Good MUCAPE and effective bulk shear, MESH over 1", and moderate satellite growth contributed to an 80% probability at 19:00 UTC. The forecasters on the San Angelo, TX desk issued an experimental severe thunderstorm warning at 19:27 UTC, noting the high ProbSevere value and a lightning jump that helped in their decision making. A tornado warning was also issued on this storm by our San Angelo team.

Figure 2: A storm far from any radar in southwest Texas.

An official NWS warning was issued at 19:45 UTC (see Figure 3), 45 min after a ProbSevere value of 80%. No LSRs have been recorded yet.

Figure 3: ProbSevere (Prob=98%), composite reflectivity, and an NWS severe thunderstorm warning.

-Cintineo

CI in a Different Environmental Conditions

Here is an example where the convective initiation algorithm performed poorly (click to animate):

In this example, both instability and shear were very weak:

In contrast, here is an example where the convective initiation algorithm performed well (click to animate):

In this example, there was moderate instability, but shear was still weak:

From these examples, it appears the convective initiation algorithm (which uses environmental parameters) doesn’t do as good a job in poor environmental conditions. The algorithm especially seems sensitive to instability.

Mahale

Pre-Convective Forecast for EWX (San Antonio)

Main issue for today is airmass recovery behind initial eastward propagating MCS now located at the eastern edge of our CWA. Our western half of the CWA more favored for SVR this afternoon due to a greater chance of recovery. Current CAPE profiles from the GOES sounder indicate ongoing airmass recovery along the western edge of our CWA, with CAPE values approaching 1000 J/K in the west and AOB 400 J/KG in the east. CIN is rather low/near zero over most of the area, so storm coverage could be high, which would limit overall severe potential.

18Z GOES CAPE

However, model guidance suggests that afternoon CAPE profiles (~1000-1500 J/KG) and deep layer shear (~40 kts) will be favorable for organized convection, with potential for severe hail/wind and perhaps an isolated tornado with any supercell structures that could develop.

ERTEL

CI Trends over Mexico

The CI product did a pretty good job of capturing the initiation of cells to our west over Mexico. The image below at 1630Z shows CI values over the center of the image at 31%. The next scan (1645Z) showed an increase to 53% and by the next scan (1715 Z) CI dropped out since the cell had initiated. It would have been interesting to see what CI trends would have provided if the satellite was in RSO or if there would have been a scan at 1700Z.

1630 UTC

1645 UTC

1715 UTC

ERTEL

Lots of ProbSvr

Here is an example of where ProbSvr can hurt and help. In a large swatch of rainfall and embedded thunderstorms, the ProbSvr picks up almost everything. This would be a situation where “turning off” the model under a certain percentage would hide these probs that are under 5-10%. It gets messy!

Lauren

Lightning Spikes, Prob Severe Follows

I am noticing a trend that ENI Lightning Jumps are acting as a precursor in today’s environment to increased Prob Severe probabilities. The trend is developing after a few observations with early initiations in the far west part of our CWA border.  The first image is an example of an ENI jump, please focus on upper right panel (data point 2).

Prob Severe has been a very helpful tool through the week. As we analyze more discrete cells developing and moving east into the SJN CWA. In this cases, our data display from ENI has been much cleaner and seems to help guide the forecaster.  The correlation to lightning jumps and storm intensification will continue to be monitored in today’s environment. The image below demonstrates the increasing prob severe probability just minutes after our ENI lightning jump (bottom left panel, <70%)..

SPC Mesoanalysis vs. GOES-R LAP Algorithm Precipitable Water

Here is an example of precipitable water (PW) from the SPC Mesoanalysis and observed from the GOES-R LAP Algorithm:

While there are slight discrepancies between the two data sets (and obvious noise in the GOES-R data), they are actually fairly similar with respect to trends and location of the highest PW values. The gradients of PW match very closely. This tool will be very useful to track increasing precipitable water.

Mahale

CI Prob Performance in Cirrus

CI Prob shows several areas for possible thunderstorm development in central and west Texas. While CI Prob has yet to verify at the time of this blog post for much of the region, it has done a very good job in eastern MAF CWA.  The CI Prob increased from 1630 in this region when nothing was showing on radar or prob severe. CI Prob led the way.

As the storms initiated, CI Prob continued to indicate growth of other cells. This, too, was verified on in the far west portion of SJT CWA. This provides forecasters with more confidence in CI Prob, even initialized under cirrus in this event, as additional storms are forming along this area.

UFFSU

GOES-R LAP Error

This is not normal.

-Champion