Cloud Layer Impacting CI Prob

Showers, thunderstorms are initiating in our western cwa. This initiation was first noticed on satellite with rising clouds tops evident. Reflectivity started showing up at approx 1815z. These showers continued their development through the course of time. Satellite easily shows instances of this. So far, CI Prob was not picked up on this developing trend at all. No probabilities with CI showed until 1900z.  These is after storms have initiated that are at or greater than 40dbz. Will continue to watch CI Prob through the afternoon as additional storms to initiate to see if pre-existing cloud contamination throws CI Prob off.

1815z

1900z

Larger Scale GOES Features

As we wait for storms to develop in MAF, I am monitoring a few GOES-R products to track the impeding chance for storms and severe weather.  Higher layer CAPE values continue to move into the cwa, especially the eastern half. There is some moisture potential available in the atmosphere, demonstrated by layered PW. The PW is not necessarily high, but existent with a surge as far west as our New Mexico counties in the cwa. There is a steep decrease in CAPE and PW in the extreme western portion of the cwa.  This encourages the forecaster to focus attention in central cwa for development through the course of the afternoon. UFFSU

MAF Mesoscale Thoughts

A few interesting features setting up today in the MAF CWA. Initial CAPE values and moisture are increasing/advecting in from the S-SW from 17-18z. CAPE is also showing some “bulls-eye” like features in SJT’s area which is probably not correct but still gives us an idea for a focus of convection. It is not clearing out well with a thin layer of cirrus. Even then we are starting to destabilize. There is a dry line sitting N-S and stretching through SW Texas with dewpoints to the east in the mid 60s and in the mid 30s to the west. The shortwave aloft is still back in eastern Arizona which is where the upper support is going to come from. I think it is going to be a race between the dry line pushing through and the upper shortwave moving in. Model guidance has the line/instability pushing quickly east so if we don’t initiate in the next few hours it may end up too dry for anything to pop. There is good deep layer cape/shear so if we can start to initiate the storms will likely be strong. As of 1850z, there are a few showers showing up in the NM counties so we will see how those evolve.

17z CAPE

18z CAPE increasing

17z PW

17zPW

18z PW

18zPW

Lauren/Mahale

GOES-R PW forecast for initiation

A quick glance at the GOES-R Layer PW as of 1800Z May 13 reveals a large pool of moisture with PW values around 1.8 inches in southeast Texas.

A curl of 0.75 inch layer PW extended up from the main pool, butting up against the mountains of eastern New Mexico.

Anticipating storm initiation within this area, with cells developing and moving into northwest Texas and the Lubbock CWA later this afternoon. Kick-off will likely be late in the afternoon due to the thick cirrus cloud layer currently over the area. CI is trying to pick up on  a couple cloud elements over eastern New Mexico as the cirrus begins to clear from that area.



Stay tuned….

~Regina Phalange

Daily Summary: Week 2, Day 3 (May 13, 2015)

In contrast to yesterday, today our forecasters received a warm welcome to South Texas, operating close together in Houston (HGX), San Antonio (EWX), San Angelo (SJT), and Midland (MAF). Forecasters were once again exposed to an blend of ongoing convection caused by a very large precipitation shield to the East and fairly consistent developing multi-cellular/linear convection in southwest Texas ahead of the dryline and inside a narrow corridor of instability. Today we saw extensive evaluation of the ENTLN lightning trend graphs, Lightning Jump, ProbSevere, and GOES-R CI and had a fair amount of coordination between teams of adjoining CWAs.

In an EWP first, each of the three teams issued a warning covering a single storm from three different CWAs. After a round of applause, forecasters were back at work.

Overall, an interesting day after a fairly pessimistic morning briefing. Here’s hoping for a strong finish tomorrow as we will most likely continue operations in West Texas.

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


Feedback from Daily Debrief
- Bill Line, SPC/HWT Satellite Liaison

GOES-R LAP.
- PW did well – represented the gradients closely. With spc meso, was within 10%.  Gradients and advection were represented well.
- Only bad thing is the striping, sharp, unrealistic gradients.
- Did a good job with axis of instability, convection developed along the gradient, where one would expect

NUCAPS
- I looked at a sounding (modified) ahead of the developing convection in Texas; it showed that the environment was quite unstable with adequate moisture. To the west, much less instability and little moisture in the profiles. Storms moving into the area of the first RAOB grew strong and produced severe, with no new development to the west.

GOES-R CI
- It did much better than the past few days, maybe cause there was less clouds around, keyed in on initial cu development. I was able to see a trend, increase in probs, then storms went in satellite. Would be helpful as a border cwa, to use data in mexico, to see where storm would go
- When we switched to midland, did well showed development along a line right away
- In South Dakota where instability was weaker, it did not do well. In florida where instability was abundant, it was doing better.
- Concern in San Antonio was if it any storms along the boundary would reach us, seeing CI pick it up told us that something would build south, and indeed move into our CWA
- In San Angelo, ci was keying before storms first formed, once it started, gave increased confidence that line would continue to grow. Was some cloud cover to start too

ProbSevere
- Storm went up to 89% scan or two before we issued warning. When warning was almost expiring, we were sure exactly what we wanted to do. Probsevere started to come down, plus not looking good on radar, used this to expire warning.
- I issued a severe thunderstorm warning based on just probsevere. Glaciation and updraft both strong. I placed polygon same time that probsevere reached its max. Seeing rapid increases in probs increased my confidence to issue severe warning. Three body spike soon after. I used only the base reflectivity and ProbSevere to issue the warning.
- Useful to have lower values to see ramp up in probs, blocking out low probs would cause us to miss some trends.
- A time trend graph in probs would be useful to see
- I liked using it with mrms underlay, times match

Lightning jump
- Negative LJ was a sign of rapid storm dissipation, before storm weakened. Perhaps there should be a color scale for the negative “jumps”.
- It did well at capturing upward trends, but easy to miss them with the 1-min updates.
- Sometimes chaotic with different values in LJ from scan to scan.

PGLM

Visualizing Lightning Data

Here is an example of a display that I tried today that seemed to really help with analysis. I liked it since it kept the time series on the side and allowed for interrogation of the other data sets in a larger main editor and at the same time I could quickly glance at the lightning time series to determine the trends in lightning data. In the display, the northern cell goes with the top right time series and the southern cells goes with the bottom right time series.

Ertel

HWT Interoffice Coordination!

What a great time working with our neighboring offices for a severe cell moving into the three corners of our CWAs. Thanks Midland and San Angelo for the great coordination!

ERTEL/Lauren

Hits and Misses in OT Detection Algorithm

Here is an example showing some hits (in green) and a miss (in red) for the OT detection algorithm. Thankfully, the better resolution of GOES-R should help with OT detection!

Lightning Jump Sample

Image 1.  The Lightning Jump showed a 2 sigma at 2358Z (left image) in southwest TX.  The cell was in the process of strengthening at that time (right image).

Within 10 minutes the storm strengthened and showed a TBSS.

Will note this is using 0.5 degree and is 18,000 ft AGL about 130 nm away from the radar.

The Lightning Jump increased to a 4 sigma at 0010Z (left image).  A few minutes later this was reflected in the radar (right image).20

-Champion

ProbSevere in Warning Decision Making…Part 2

Here is another example where ProbSevere rapidly increased form 18% to 94% (click image to animate):

The normalized vertical growth rate and the glaciation rate were both strong. In this case, I was confident enough to use the ProbSevere by itself to issue a severe thunderstorm warning. I started drawing the warning polygon prior to the highest percentage coming from ProbSevere. In the end, my polygon was issued nearly coincident with the highest probabilities.

Mahale