Prob Severe and More Confidence in Storm Strength

Much of the storm environment across the Raleigh CWA was pulse.  I noticed that the Prob Severe was also "pulsing" up and down throughout the loop below. Updrafts would intensify and then quickly weaken and Prob Severe was also indicating this trend. This gave confidence that any storm would quickly strengthen before it quickly weakened and warnings were not necessary. When Prob Severe would show an increase in probability, mainly for wind, the next update would show a quick decrease.

The "pulsing" of the Prob Severe gave me confidence a warning is not necessary and that the storms would quickly weaken. 

-Ironman

ProbWind Under Forecasting Probabilities

Here is an example where it appears ProbWind under forecasts the probability of severe wind:

In the example above, there is widespread >=50 knot velocities associated with a line of thunderstorms; however, ProbWind only had a 1% chance of severe winds. This was likely because of relatively low azimuthal shear due to weak azimuthal gradient.

It would be beneficial to include some variation of maximum radial wind (such as  to ProbWind to account for the cases where the azimuthal shear is relatively weak.

-Lost Met 

AWIPS SA Procedure

Tested a recommended 3panel SA layout (below) with vis, IR, and radar data. Overall, simple and easy procedure use. If it were possible, it would be nice to be able to time lock all three panels together. In this case, just the left 2 panels were synced while the radar was separate. It would be nice to evaluated all 3 simultaneously in time and also with a cursor readout to establish trends in reflectivity and also IR temps. Think this is just a limitation with AWIPS2. --Tahoe

GLM Color Scale

I utilized the 5 minute GLM Event (1 minute update) with the 5 minute flash (1 minute update to monitor trends in lightning along with other GOES-16 data VIS/IR and radar data.

Here is an animation of the GLM data over the KRAX domain.

I do prefer the color scale above over the more typical gridded color scale. However, I think it may be useful to have the grey colors more white so the higher values stand out a little better. This could be an issue if being overlayed with Visible data. Increasing GLM events and flash data coincided very well with when cells were strengthening.  When GLM events and flash data decreased, cells were weakening. The faster updating GLM data also helped show trends in the storms quicker than just viewing radar data alone.

-Ironman

ProbWind potential enhancement?

One great part of the EWP at the HWT is the ability to discuss ideas with forecasters in response to something they are viewing in realtime.  One forecaster covering the Boston WFO and I were discussing the ProbWind values with the squall line in western MA around 2030 UTC.  The forecaster noted the ProbSevere (ProbWind) values diminished (from 60-70% to 20-30%)--largely in part due to decreased MRMS AzShear values.  The screenshot below shows the single radar 0.5 degree base velocity imagery.  The imagery shows two important features 1) the lack of a gradient in the velocity leading to somewhat low AzShear values and 2) at approx 3300 feet above ground level winds near 55 knots.  The forecaster looked at base velocity values from earlier in the day when severe reports occurred and noted the current velocity was more intense--which lead to him issuing an experimental severe thunderstorm warning.

Figure 1.  KENX 0.5 degree base velocity imagery valid at 2034 UTC 19 June 2017.

While such a product does not exist, we discussed the potential utility of an MRMS Maximum Velocity Magnitude product (for a series of levels or layers like 500m, 1000m, 1500m, 2000m, etc. AGL) and how such a product could potentially further improve the ProbSevere ProbWind predictions.  These types of interactions are extremely valuable and perhaps such a MRMS product is worth considering.

-Sieglaff

Use of GOES-16 Vis/IR 2 Panel and Radar Situational Awareness Screen

One way I was able to monitor trends in convection was using a 2 panel display of 1-minute visible and 1-minue IR next two a radar display which included Prob Severe. Warming cloud tops as well as a more smooth look on the visible imagery gave me confidence the storms of concern were weakening. This coincided with Prob Severe values decreasing fairly rapidly.

Other cells are developing on an outflow boundary well to the NW of the first band of convection, and this display has been useful in monitoring the trends over the last 30 minutes.

-Ironman

KRAH: SVR 1954z

ProbSevere Analysis: 2 main areas of interest, partner took northern cell and I took southern. Focused on the high ProbSevere area of southern cell.

• Started looking at this cell with ProbHail & ProbWind were steadily about 80% with development  along the southern part of the line. 
• Focused on that cell from ProbSevere, looked at the 1 min Vis and saw a nice look and development to the Cbs. Even though Z aloft wasn't that big, the trend was increasing.
• Thought threat would be marginal for hail and more so wind from precip loading and cells that have had a history throwing out outflows. 
• Didn't have great confidence in this cell, particularly when the GLM data didn't show an large uptick in lighting event output prior to issuance.
• Result: Cell quickly collapsed, ProbSevere values dropped and no reports were received...yet. 

     --Tahoe

ProbSevere Hazard Specific Products

Across the northeast, specifically in the Boston CWA, the primary threat today is damaging wind gusts. It might be beneficial, especially when there is only one hazard expected, to have an option for individual ProbSevere products (i.e., ProbHail and ProbWind) like ProbTornado.

That way the forecaster can easily look at the specific information that goes into each hazard rather than looking through a long list of information (as shown below):

There is an option to view a "ProbSevere Light", but it will still be beneficial to view all the information that goes into a specific hazard. 

-Lost Met

KRAH: Prob Severe Model

 Issued a Severe Thunderstorm warning for the northern cell on a broken line of thunderstorms to the southwest of the KRAX radar.  The Prob Severe model indicated 92% on ProbWind and 80% and ProbHail. The storm interacted with an outflow boundary and quickly intensified.

 

About 5-10 minutes after I issued the warning the cell weakened.  

Another cell attempted to strengthen about 30 minutes after the issuance of the warning. The cell moved into the southern portion of my original warning box. Prob Severe briefly indicated wind probabilities around 80%, but it did not persist and continued to weaken thereafter. Seeing how quickly the first storm dissipated as well a quick drop in Prob Severe led me to not issue a new warning on the second cell. 

-Ironman

EWP Underway for 2017

The forecasters are spinning up on their WFOs of interest for the afternoon (Boston, MA and Raleigh, NC).  The NOAA/CIMSS ProbSevere in 2017 has been improved based on feedback from previous EWP experiments. For 2017 EWP, forecasters are evaluating ProbSevere 'AllHazards' with specific probabilistic forecasts for severe hail, severe wind, and tornado.

As of mid afternoon, convection was rapidly intensifying in the Raleigh WFO. Figure 1 below shows AWIPS-2 screenshots of ProbSevere evolution between 1848 and 1936 UTC.  The ProbSevere values increased steadily as thunderstorms developed along a low-level convergence zone and then really increased as an outflow boundary moving from SE to NW impacted the storms.  The ProbSevere values were largely due to a wind threat (ProbWind), although close to 1936 UTC the ProbHail values increased markedly with precipitation core intensification (note jumps in MRMS MESH), perhaps owing to interactions with the outflow boundary.  As of this writing severe reports have not been received.

Figure 1.  KRAX 0.5 degree reflectivity and NOAA/CIMSS ProbSevere contours and readout.  Valid 1848 - 1936 UTC 19 Jun 2017.

The EWP Raleigh WFO team are evaluating these storms and have issued experimental severe thunderstorm warnings.

-Sieglaff