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Real-time posts made during testbed nowcast and warning operations.
Below is an example of a case where prob severe my offer the best option for a warning decision. This storm is outside of the best RADAR coverage available; however, strong development has been seen on Satellite imagery for an extended period of time. In a case like this, the PROB Severe Algorithm may be the best option for a warning decision, based on the data available.
South Beach
Figure A
Figure B
Best Practice: Look at lower left image on both Figure A and B (GLM Minimum Flash Area), notice Figure B has interpolate turned on which makes the product less useful since outer edges also have minimum values. The GLM Minimum Flash Area of interest jumped out much better on Figure A without interpolate turned on.
Figure C
Blending both All Sky Sfc-900mb PW and Visible satellite imagery together for convection initiation in western TX panhandle.
Photo above shows a double maximum in AzShear. One of these is clearly colocated with a TOR on ground via CC. However, velocity shows two very different situations, possible strong tornado on ground versus convergence along the RFD gust front. If you were just looking at the AzShear product, both of these areas would be cause for concern, when in fact the impacts are extremely different. Would be nice to be able to differentiate between extreme high values of AzShear near a tornado versus more broad convergence on any wind shift area.
This next image shows a region where the AzShear maximum is too broad. This may simply be a color table issue, but clearly there is an area within the white region where a tornado is on the ground, and other regions within that max where only general convergence is occurring.
This image shows a location where some ground clutter is producing a false positive and negative AzShear couplet. Mathematically it makes sense to see this here given the V data, however to an untrained eye or someone just solely depending on AzShear you could be led astray.
A positive of AzShear is that it can highlight areas of potential concern down the road. The above frame was just one of several frames showing strong convergence and high AzShear values preceding a second tornado from the main cell 10 minutes later. This could be particularly helpful in QLCS storm modes where convergence and shear increases in a broad sense along the main line prior to tornadogenesis. Also in this particular case, the V data was not entirely conclusive that convergence was increasing. AzShear was very conclusive here.
Dusty Davis
Did a quick check of the merged TPW and AllSky products and as previously advertised/anticipated, the convection has been riding right along the gradient of the higher instability, but there is some discrepancy as to whether it’s right in the heart of the higher PWATs or along the leading edge, depending on if you’re looking at the AllSky or TPW, respectively. Noticed quite a bit of a latency in the availability of these products (up to an hour), which wouldn’t be good in an operational setting. Compared the values of the TPW and AllSky PWAT with the RAP, and the AllSky matched up much closer to the RAP. However, with the amount of cloud cover in the region (for obvious reasons), the GFS is the predominant data type (basically a model-to-model comparison). Either way, the general idea/trend is helpful if serving as a mesoanalyst in an operational environment.
~Gritty
(CAPE)
(AllSky PWATs)
(Merged TPW)
This is an example how the DSS meteorologist could use RGB imagery, gridded lightning products, CG lightning, and range rings for event support.
In this case – we are a HYPOTHETICALLY supporting the Panama City Music Festival denoted by the 10nm range rings. Process would be to monitor products to predict when lightning is likely to impact an highly vulnerable population.
Here is one drawback of ProbSevere that has been briefly discussed. The areal extent of the identification is not based off of some of the features that feed into it, but rather the dBZ reflectivity representation. In this case, for a MCV and line of storms, the blob below is approximately 152 miles long using a center line to calculate the distance. ProbSevere kept this size of storm for two 2 minute calculations before breaking the storms apart into several different identifications.
-Alexander T.
ProbTor did a decent job on pinging the developing waterspout off of LIX’s coast. As for lightning, the MFA was the first to show a response that bore paying attention to, with the ED/FED products maxing out later, as the circulation tightened and the cell matured.
~Gritty
Compared the NUCAPS sounding today (4/25) over WFO TAE. See the point evaluated below (labeled point A below):
This is the “unmodified sounding.” Overall the thermodynamic profile looked realistic. Looking in the PBL – noticed it was about 2C too warm and about 2C to dry.
This is the “modified sounding.” As expected, no change to the mid level thermo profile. The PBL did have the “correction” applied – not the “cliff” in the temp profile. Overall, I was expecting a more sophisticated PBL nudging scheme. In reality – it just appeared to force the T/TD from the nearest METAR, with maybe some minor smoothing. This is something a forecaster could do in about 30 sec – so didnt gain much.
BETTER OPTION: employ a more sophisticated nudging scheme to the nearest RAP/HRRR. If you going to modify the sounding – might as well nudge it to a model analysis – which have a long history of being used in severe wx research.
Forcing and storms remain well to the west of our CWA, but the atmosphere is becoming primed for strong to severe storms later this afternoon. LAPS All Sky retrievals show that ML instability has been steadily building, reaching roughly 500 J/kg along the Gulf coast.
An 8 hour loop shows how the instability has built and gives more confidence that instability will continue to build ahead of the storms to our west. 
We did feel that LAPS CAPE seemed a bit underdone given the intensity of the downstream of the convection, so we took a look at the latest NUCAPS retrievals. We examined the point in the extreme SE of our CWA.
The boundary layer on the unadjusted sounding required some adjustment to match the nearest obs, but overall, seemed to capture the general profile well. I was initially skeptical about the warm nose just above 700mb, but a similar feature was evident on the 12z sounding from TAE. This feature may have an impact on storm intensity and potential hazards, and it would be particularly helpful to see how this feature changes over time.
Sandor Clegane
GLM does a good job at capturing large flashes that appear in the stratiform region behind lines of storms. In this case looking at the Total Optical Energy for 5 minutes with 1 minute updates you can see the large flash show up (the yellows and the whites). Reflectivity from KMOB and Visible satellite are layers under the TOE data.
This large flash has Minimum Flash Area values between 1100-1700 km^2 with the Average Flash Area anywhere between 2700-3600 km^2. This is a large flash that extends back into the stratiform region (the Anvil) of the cumulonimbus clouds. You can see the lighter precipitation on the RALA (Reflectivity at Lowest Altitude) product below. The darker blocky outlined area is the Average Flash Size with other variables in the 4 panel.
One important operator note is to be careful what you time match with the GLM lightning data. In this case another forecaster had time matched with the 1 minute meso-sector of satellite and because of errors in that data the large anvil flash was skipped in the one minute GLM data. If the GLM data is the focus of your analysis always remember to time match with it and then use other data (like satellite or radar) on those time scales.
-Alexander T.
