Value of storm-top information

Forecasters working in the Rapid City, SD CWA noted some storms finally showing signs of strengthening in western Nebraska, with cores developing on radar and evident in 10.35µm channel imagery. The toggling of images below shows development of rapid cooling on the northwest end of a large mass of deep convection (Fig. 1). A forecaster noted that the satellite growth rates were N/A in ProbSevere (Fig. 2). This is because the region was already "attached" to the thick cirrus mass to its southeast. We discussed using cloud-top features, such as rapid storm-top cooling and OT detection/persistence quantitatively in ProbSevere. The forecasters noted that these features are qualitatively good indicators of storm strengthening (or weakening, when there is warming). GOES-16 data enables forecasters and researchers to see storm-top features and evolution much more clearly than before.

Fig. 1: 10.35µm brightness temperature. See the rapid cooling on the northwest end of the large cirrus mass, near the cursor arrow.

Fig. 2: ProbSevere and MRMS composite reflectivity. Note that the satellite growth rates were not discernible for this storm (N/A). 

A very strong cornfed storm

Just after 7pm a monster storm developed southwest of Hastings, NE. At 732pm the storm intensified to near 70 dbz up to 32kft! The MESH product showed just over 2″ hail and the RSO showed nice bubbling of the overshooting top on visible satellite. This was definitely picked up by the overshooting top algorithm. Ironically, the lightning was never really all that impressive, but did hold steady. The lightning level really dropped by the time the maximum storm strength was reached.

Overshooting Tops Galore

Multiple severe thunderstorms in the Hastings CWA. The algorithm lines up very well with where overshooting tops are observed on the visible and with our current SVR Warnings.

-Shasta

Overshooting tops in IL

Picture below shows 5 overshooting tops in or very near LOT CWA.

Continuing the Severe in Dawson Charley

Initial thinking from radar data is that cell is starting to die down, but did have a few more upticks in overshooting top product.  Cell is no longer deviant in motion and got a new warning out to cover its trip back to the northeast.

Extending SVR eastward Charley

Continue to have an overshooting top and good DVIL with this line.  Had some stronger wind gusts and at an airport in Valley county (53 mph).  Near severe and extended the warning through the likely gust front area north of the higher DVIL storm.

Another Severe for Dawson and Gosper Counties Charley

Continue to have an overshooting top.  Also heard a report from a neighboring CWA of 57 mph winds in Custer county, a little out ahead of my previous warning box.  Decided to go ahead and issue a downstream warning to cover that area as well.

Still have tall cells in the middle, matching up with that good OT.

SVR in the northwest, Charley

OT product showed a good updraft.  Also saw signal for a strong updraft in the Dawson county part of the line with 60+ knots inbound winds at the storm top.

ProbSevere should not be useful, given this cell had been around for awhile and was more of a line, but still high.  Time series showed lightning dropping though further inspection showed lots of cell mergers and breaks occurring.

Rapid Scan

Looked at this briefly. Looping quickly, we were able to track the inflow to our storms in LBF. The overshooting top algorithm jived with the strongest storms in the DMA across SE Lincoln Co. -BT

CI and Overshooting Top observations

Living vicariously through Minneapolis and Aberdeen…

The 2130Z Visible with the overshooting top and CI overlaid shows a few interesting things. There is currently an overshooting top with the strong/severe convection over Grant County, SD. Current IR Imagery shows a core of -58C surrounded by a broad downwind anvil of approximately -53C. There is a tighter gradient of cloud temps on the upwind side of the anvil, with temperatures on the edge dropping quickly into the upper -40s C.

Also, the CI values began to highlight an area east of the ongoing strong convection with two scans showing greater than 90% chance of convective initiation. On the corresponding 2130Z radar image out of MPX, only a weak shower is shown.

Fast forward to the

Flash Forward to 2207Z, there has been no further development with the cell that showed promise in the CI in Pope County, MN

-Shasta

SRSO and Overshooting Top Stationary in PA=FFW

SRSO shows several things. First the overshooting top in PA was nearly stationary, anchored to the terrain by the southerly inflow impinging on the inflection point in the Appalachians. Dual Pol radar estimates up to 3.5″ rainfall there near Harrisburg, PA and a Flash Flood warning was issued for the area. A couple of the overshooting tops including this one were caught by the algorithm (denoted by the red grids in the visible imagery)  but one to the northeast was not as seen by visible imagery.  Also of note in the SRSO were the north south cloud streets in MD and the Chesapeake Bay breeze front just east of KBWI with cooler temps in the 70s and lack of clouds over the Bay into southeast PA. MrSnow/Wacha

Warning 1

Issued a warning on cell over Humphrey’s County…storm was in an environment that had already produced storms with severe hail. Noticed that it had not yet produced an overshooting top but looked close using the one minute Super rapid scan imagery also noticed local maximum area of cape out ahead of where the storm was developing with clear skies

Notice the lightning jump on the ENI time series…this may have added urgency to issue a warning had I used it to begin with. Did get wind damage reported and power outages with this cell.

Inthecards

Multiple Overshooting Top Examples

This loop shows a few examples of the overshooting top detection algorithm in action. Even though the overshooting tops were already pretty obvious in visible satellite, the detection algorithm really helped grab my attention.

(Click image to see animation)

-Helen Hunt

Nice example of Overshooting Tops Tool (JAX/CHS)

Noting a lot of overshooting top development on the supercells across the northern portion of the Jacksonville CWA as well as into neighboring Charleston, SC’s CWA.  The overshooting top (OT) algorithm picked up two supercells across Long and Bryan counties in SC at 2030 UTC.  With the current sun angle, you can see the Long county top, but not so much on the Bryan one, but the OT tool show them both well.

Figure 1:  Supercells with overshooting tops across southern SC at 2030 UTC.

We can also use the OT tool anytime, day or night, as it is based off the IR satellite data.

CoonieCatEye

Overshooting Top and ENI Time Series Comparison

We noticed a significant ‘lightning jump’ around 1820Z in the ENI time series which was indicative of the updraft increasing in strength and size. Not long after that at 1830Z, the overshooting top detection picked up on an overshooting stop associated with the same storm. It makes sense that we would see the lightning jump first, then get the overshooting top detection a bit later as the momentum of the growing updraft catapulted it over the tropopause.

-Helen Hunt

Overshooting top algorithm in Montana

At roughly the same time as our big convection was happening with the high reflectivity and climb in lightning frequency, the overshooting top algorithm was triggered.

Image from 2210z.

Jason Williams

June 2 — Rapid growth of 2 supercells across northern CYS CWA

We have been seeing amazingly rapid supercell growth of two cells, one just north of Guernsey and a second near Lusk since 2045Z.  Both cells have also shown rapidly increasing severe probabilities.  The Overshooting Tops algorithm was also indicated with the Lusk cell.

The 1-minute GOES-14 visible satellite is showing both supercells very well (L).  The two pink overlays indicate the increasing severe probabilities.  The southern cell north of Guernsey was up to 90 percent, while the cell near Lusk was at 76 percent.  Since 2107Z, the Lusk cell severe probabilities increased to 89 percent at 2110Z. along with several CG lightning strokes.  The 2107Z Flash Density (R) was up to 17/minute with the Gurensey cell, and 10/minute with the Lusk cell.

CoonieCatEye/MacGyver

June 2 — Lightning Jump coincides with Large Flash Density (CYS)

Just a few minutes after my previous post on distant flash density, we got a lightning jump along with several CG lightning strokes AND a large flash density.  The lightning jump was up to 6 sigma!

Note the 6 sigma lightning jump on the left screen along with 4 CG lightning strokes, while the flash density was up to 16 per minute!

This cell persisted with its density rate as the severe probability quickly increased to 90 percent by 256 PM.  The overshootimg top algorithm also turned on with another supercell that developed near Lusk, WY.

CoonieCatEye

Thoughts on Overshooting Tops and 1 min imagery

I was trying to think of how to use the overshooting top algorithm in warning ops.  The current 15 minute data it is useless to me.  I would be interested in the trend and the duration of the overshooting top for issuing warnings.  The longer the overshooting top, the more likely it will have severe weather.  As a result, the only data that would work for me is 1 min data.  I can compare this to the radar data as I get it.  I do not think that the 5 min data will work as it will wash out trends and the true nature of the atmosphere.

This made me think of QLCS and HSLC tornadoes.  If I had near real time one minute satellite data, I could find the strongest updraft in the line.  This could have a huge impact on these warnings, the FAR and POD for these storms.  The other thing that would help this would be a local maximum cloud top algorithm.  For example, make a 200 km x 200 km grid.  Use some nearest neighbour algorithm and find a local max in cloud tops.  This could lead to lead time with QLCS and HSLC storms.

Williams and MacGyv

Evaluation of products during ILM tornadic storm

Tornadic storm in eastern Columbus / western Brunswick Co NC around 2010Z to 2020Z.0521 ILM 4 panel B

Prob Severe
2004Z – model merged cells, value at 79%
2012Z – prob severe peaked at 95% as tornado was likely occurring
From 20Z to 21Z the storm moved from a 1600 ENV MUCAPE environment to 2100 CAPE environment.  Over that same time ENV EBSHEAR dropped slightly from 28 kts to 26 kts.  MESH peaked in tornadic cell at 2″ at 2018Z.
In southern cell, MESH passed 1″ at 2038, prompting severe t-storm warning.  Peaked at 1.26″ at 2042Z.

Lightning:
Pictured first is trend on cell responsible for tornado warning.  Significant weakening trend also seen on radar presentation as southern storm took over.

Lightning jump in southern storm (second picture) happened between 2030 and 2035, several minutes before severe hail indicated (above).




Overshooting top: detected over most of the 20Z to 21Z time frame


PHI tornado product




-Holaday