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.
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.
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.
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.
I found creating a 4-panel of LAP data (below) useful to our mesoscale analysis. While the data was 2 hours old, we were still able to get a feel for the convective environment in the KRAX CWA. This will be a useful tool to supplement SPC mesoanalysis data since it utilizes observations from GOES-16 satellite rather than fully relying on a model. The updates are also a little more frequent than what is found on SPC. Including the data type helped to indicate some of the gradients and the reason for the pixelling of some of the data. This can give forecaster more confidence when its indicating clear or cloudy versus soley on the GFS, which could add uncertainty into the data. Other variables in LAP such as K Index and Showalter are not something I typically use, so I left these out of the 4-panel.
At first glance, the scale/labeling on the Data Type were confusing. One potential change would be to have wording such as partial cloudy (for cloudy retrieval) or something along those lines to better differentiate the categories.
Note: the time of the data was 2 hours old during analysis.
Big concern is with the northward propagating outflow boundary and its imminent convergence with the northern most band. (below)
Monitored initial ProbSevere numbers but feel this may be moot as the line is about to be modified by the outflow boundary.
Solely evaluating environment using satellite LAP data to get an idea of the the environment between the outflow and northern line. Only issue is the LAP data is almost 2 hours old and roughly evaluating the convective environment from it.
The LAP 4 panel (below) reveals an environment with plenty of moisture and instability to promote further development and propagation for convective activity.
Ideally would have liked to overlay radar on the LAP output to see development along gradients, but not possible due to the old LAP data.
This is a great SA tool to stay ahead of where you expect convective activity to continue or diminish.
My take away from this analysis is: Atmosphere is primed to support long lived convection along the SW-NW swath through the RAH CWA.
Will now monitor radar trends, particularly interested to see if sharp trend start occurring in the ProbSevere.
There are some inaccuracies with the derived motion winds when compared to surface observations. Here is an example with the 1000 mb wind speeds (near surface) and METARs:
Note the significant discrepancy in both speed and direction.
It also appears the clouds are moving southwest to northeast (opposite of the wind barbs).
In addition, I would suggest color-coding by pressure level rather than wind speed because wind barbs (by definition) already provide the wind speed information.
The Hazardous Weather Testbed 2017 GOES-R/JPSS Spring Experiment is underway in Norman, OK. The experiment will last for four total weeks (June 19, June 26, July 10, July 17) and include three National Weather Service forecasters and one broadcast meteorologist each week. Participants will have the opportunity to evaluate imagery and derived products from the GOES-16 Advanced Baseline Imager which recently became available to forecasters in AWIPS. Additionally, HWT participants will be the first forecasters to evaluate the GLM lightning data in AWIPS. An updated ProbSevere Model will be demonstrated and include separate ProbWind, ProbTornado, and ProbHail probabilities. Finally, NUCAPS from JPSS will be demonstrated, including evaluation of the operational NUCAPS algorithm from Suomi-NPP, NUCAPS from MetOp A/B, and experimental NUCAPS product that is automatically modified in the low-levels.
Stay tuned to the blog for posts made by our participants and visiting scientists. Unfortunately, GLM data posts will not be available to the public due to the early testing stages of the data.
An energetic, negatively-tilted shortwave trough traversed the middle of the country last week, bringing several bouts of severe weather to the Great Plains. By visualizing the accumulation of the ProbSevere output (storm centroids ≥ 50% [pink boxes]), the NWS warnings (orange and red polygons), and storm reports (blue, green, and red circles), we see that the ProbSevere model handled the first event on October 4th quite well, at least qualitatively.
Figure 1: A toggle between the 12Z 10/4 ->12Z 10/5 accumulation of NWS warnings and reports, with overlaid ProbSevere centroids greater than or equal to 50%.
A very long-lived storm that approached the Norman, OK area produced numerous hail reports. It was first identified at 23:47 UTC, with a probability exceeding 60%, due to high effective bulk shear, MUCAPE, and strong satellite growth rates. The MESH was 0.24" and total flash rate was only 1 fl/min. After quick jumps in the MESH (to ~0.5") and the flash rate (to almost 20 fl/min), the probability exceeded 80%, and was promptly warned at 23:52 UTC. We can see a time series of the ProbSevere probability (thick red line) and constituent predictors in the time series below. Note that the satellite growth rates were both 'Strong', and expired a little after 02:00Z. We can also see when NWS warnings were valid and when severe weather was reported in the lower subplot.
Figure 2: Time series of ProbSevere and its predictors (top), and NWS severe weather warnings and severe weather reports (bottom). The axes on the right are associated with the time series on the top subplot, while the legend in the lower right is associated with the bottom subplot.
The stunning time lapse of this storm was captured by Jim Ladue (NOAA/NWS/WDTD) as it approached from the west. The range of this video is from about 23:52 UTC (when the storm was first warned) to nearly 01:00 UTC.
A second short-wave ejected through the Plains on October 6-7 (as Hurricane Matthew threatened the southeastern seaboard), bringing with it another bout of storms, and this time, numerous tornadoes. ProbSevere again handled most storms quite well, with few false alarms and a couple of missed wind reports.
Figure 3: A toggle between the 12Z 10/6->12Z 10/7 accumulation of NWS warnings and reports, with overlaid ProbSevere centroids greater than or equal to 50%.
We can see the evolution of the storms and associated warnings below, over Kansas, Oklahoma, and far northern Texas. The animation is from 18:30UTC to 00:00UTC every 10 minutes. The pre-frontal storms and those close to the triple-point (in north central KS) remain discrete longer than those which are forced by the cold front. The red, orange, and green polygons denote NWS tornado, severe thunderstorm, and flash flood warnings.
Figure 4: Animation of ProbSevere contours, NWS polygons, and MRMS MergedReflectivity from 20161006-18:30Z to 20161007-00:00Z .
