Daily Summary: Week 3, Day 4 (May 21, 2015)

Warning Activities took place in the Miami, Wilmington OH, and Moorehead City CWA's

- Bill Line, SPC/HWT Satellite Liaison

Forecaster feedback from weekly debreif:

GOES-R LAP

- Derive 1-hr., 3 –hr 12-hr  change in these products, since best utility was seeing the change in instability and moisture over a period.

- % normal tpw product would be helpful

NUCAPS

- I would like to be able to overlay other soundings in nsharp

GOES-R CI

- Have a 50 dBz product in addition to the current product

- Readout of fields that go into it would be useful to most of the participants

- Definitely a good heads up and situational awareness tool

- If in Alaska, we have a huge area without radars, so it might help here, though we have no verification. Targeting extent of shower  activity

- Would be useful to look at this product for elevated convection 

ProbSevere

- Using it with total lightning was a great combination, saw the same trends for the most part.

- It would be good to plot some sort of trend information with this (like the lightning tail with eni, weren’t really distracting). Time probsevere trend in readout would be great

SRSOR

- 15 min, you lose connections with evolution of individual cloud elements

- Yesterday looking at towering cu and there ll motion evolution and how they are sheared off

- Great situational awareness to monitor any rapidly developing feature

- I see this helping with initiation, sea breeze boundaries, orographic initiation, overshooting tops.,.. clarity on these situations is helped by 1-min imagery

- Fire weather, watching smoke plumes

- Monitoring fog and low clouds and their erosion

- Winter time snow band, elevated convective bands in winter

- Watching evololution of gravity wave features, even in winter time – might bring down stronger winds

- Tracking of volcanic ash in Alaska – we do use GOES

Lightning jump

- Esp with qlcs type event, objects were being clumped together, this is not as helpful because you aren’t seeing jumps from specific objects

- With multiples storms, tracking sigma changes in particular cells is difficult because the screen can be quite flashy. Some sort of trend info would be helpful with this too, along with other lightning info in the readout

- Had quite a bit of success looking at the sigma level, and was indicative of storm becoming severe

- Having jumps marked on time series would be helpful

PGLM

- All are very excited to see total lightning from GOES-R GLM

Late day CI increases in Carolinas

So far the increase on the boundary in NE SC has yielded a weak, small shower near Myrtle Beach.  Now probability up to 63% east of Charlotte.  The HRRR generates elevated convection in this region towards the evening.

-Holaday

Utility of 17z NUCAPS sounding in MHX

The NUCAPS sounding has shown to be a realistic supplemental piece of environmental  data the last several days.

In comparison with the 12z sounding (fig 2)…the 17z NUCAPS (fig1) sounding did subtlely pick up on a weak inversion around 700 mb and 850 mb that was evident in the 12z sounding.  The NUCAPS sounding was more moist in the 400-500 mb level than the 12z sounding…which may have been due to the cirrus advecting in ahead of approaching convection. Differences between the 12z and NUCAPS soundings can give a rough and general idea of change in environment.

In comparison…with 17z SPC meso-analysis (fig3)…MU CAPE value were comparable.

So overall…I have been pleased with the utility of this sounding for re-assessing the environment each afternoon. It may be especially useful to sample a few NUCAPS points in an area of concern to get a consensus picture of the environment.

Fig 1 – 17z

Fig 2 -12z MHX

Fig 3

Pickles

GOES-R LAP LI Retrieval Shows Destabilization, Compares Well To HRRR

The GOES-R LAP Parcel LI showed the destabilization trend through the eastern Carolinas ahead of convective initiation. The LI gradients compared well to the HRRR model – and both illustrated a sharp northern instability gradient limiting convection into Virginia. Good confidence builder and visualization tool.

Rocky

UAH CI Probs Increasing – Weak Echos On KLTX

UAH CI probabilities have increased up to 70% along the cold front moving through extreme northeast South Carolina. UAH CI probs have been slowly increasing and the highest signals do correlate to where weak echos are now showing up on KLTX.

ENI cell tracking/rate better utility than Lightning Jump in detecting tvs’s along QLCS across MHX

ENI cell/rate tracking (fig 1) was a better tool to identify and track stronger updrafts (fig 2)…within a QLCS moving to the NC coast. The lighting jump algorithm was difficult to follow one the event transitioned to a QLCS setup…because the algorithm grouped together severe cells and washed out the jump/severe signal (fig3).

Transient and weak tornadic spin-ups are noted on occasion along the NE coast with these QLCS’s in areas of interaction with discrete cells, to the north of rear inflow jets and kinks in the line.  Although both tools would likely not give much lead time on these transient spin-ups…the ENI should prove a more useful complement to radar data in these areas than the lightning jump in detecting the highest severe winds threat along the line and best potential for tornadogenesis.

Fig 1

Fig 2



Fig3



Pickles

LJDA Clustering Too Large To Take Action On

To Whom It May Concern:

The LJDA, in a general sense, clusters too large an area for proximity storms, such that action is difficult to take. In a general sense, the sigma value of the larger cluster still draws SA. The cell ID algorithm in the ENI data generally has performed well over the past two days and the polygons would offer a nice area to calculate the LJ.

Display Suggest: By merging the ENI and LJDA info, could the ENI Cell Flash Rate text info contain a “.sigma” value following the 1 min strike total. For example, an ENI cell polygon contains 45 flashes in the last minute with a 3 sigma. The text would display “45.3”.

Rocky

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

UAH Convective Initiation Watching

We’re keeping an eye out along the southwest portion of the cold front across ILM CWA for convective development. So far, SRSOR shows little cu towering and the UAH Convective Initiation is keeping probabilities around 50% or less.

Slow lightning Jump performance with SVR cell over Quitsna

At 1915z…a small supercell over Quitsna NC (fig 1)exhibited severe characteristics of 60-65 dbz above the -20c level and a low/mid level meso. Interestingly the small size of the reflectivity core and likely updraft volume limited lightning with the storm.  The 70 percent eni lightning detection efficiency in the area could also have been a factor.  This is seen in the -999 sigma lightning jump (fig 2) and only 9 cloud flashes in eni and no cg (fig 3).

It was not until 1938 that the lightning jump algorithm showed a 2 sigma jump (fig 4)…and then 1940 a 3 sigma jump that the algorithm itself would have alerted to a severe cell (fig 5)

Prob severe at 1915z was only 40 percent (fig 6)…because heavy cirrus from storms to the west negated the satellite growth algorithm.  The algorithm was consequently all weigthed towad mexh. It was not until 1925z that the mesh got big enough to have the prob severe go over 60 percent (f ig 7).

Due to the slow lightning growth…DTA were also slow in in detecting this storm. Not until 1930 for a significant DTA (Fig 8), and not until 1950z for a dangerous DTA (fig 9).

Fig 1

Fig 2



Fig 3



Fig4



Fig 5



Fig 6



Fig 7



Fig 8




Fig 9




1950z DTA MHX

Possible Borderline Severe in Nowhere Florida

There have been several storms in South Florida with ProbSevere greater than 80% and ENI Dangerous Tstm Alerts. This corresponded with lightning jumps as seen in the bottom image, but were quickly followed by equally rapid drops in lightning. ProbSevere mouse-over info briefly indicated strong Norm Vert Growth Rates and Glaciation Rates. The MESH values are topping out around or just above 1 inch. If there is any severe weather at the surface it is likely very short-lived – maybe 10 minutes or so. Nearly all of these cells are in unpopulated  areas.  In this environment we are not seeing sustained updrafts.The ProbSevere and ENI Alerts still help you focus in on the strongest storms…but in the context of everything else are not indicators (so far today) that a warning should be issued.

-snowstrm

Prob severe increasing

Radar imagery showing a storm intensifying across central Miami-Dade county (highlighted by the white arrows) due to a collision from outflow from convection to the northwest. As this storm intensified, the prob severe increased from 7% to 79% in two volume scans…as seen in the below images.

Cirrus Interfering with ProbSevere, LDJA/Lightning Had No Signal Either

As a line of strong to severe storms approached from the west, anvil cirrus continued to spread east over the forecast area. Once storms moved into the forecast area, much of the ProbSevere model analysis included N/A for glaciation and growth rate under the cirrus umbrella. ProbSevere was driven mainly by MESH, offering little lead time over the radar data use alone. The LJDA showed no sigma change or signal. Upon further inspection, the storm produced very little raw ENI lightning.

Real world: WFO Wakefield issued a tornado warning on this storm. No reports of weather with this storm as of 2022Z.

Rocky.

Cirrus tophat:

Prob Severe sampling showing N/A

Reflectivity by 1927Z with ENI Cell lightning data:

SRSOR, ENI, ProbSevere and Radar Data for ILM Warning Decision

Developing storms interacted with north/south sea breeze boundary across ILM. Initially, the 1-min SRSOR showed towering cumulus and the cloud features showed intense updrafts. At first, ENI data indicated no/little cloud flashes. However, within 1 to 2 minutes, lightning rates increased dramatically (60 to 70 per minute). ProbSevere jumped similarly  as well, from less than 20 percent to a maximum of 81 percent. Finally, using the KLTX radar data, a very impressive hail core aloft was noted with 70 dbz up to -20C (25,000 ft). The combination of the SRSOR data showed that the particular cell was one to watch, the rapid increase in ENI data and ProbSevere were excellent precursors to what eventually showed up in the KLTX data.

CI vs. radar imagery

CI imagery across western Miami-Dade county highlighted in orange peaked at 86% at 1845z.  Over 30 minutes later at 1919z, a strong thunderstorm developed in this same area as seen in the below radar image.  This is further justification that the CI tool seems to work really well in pulse environments.

LJDA Sigma Jump of 7 and 5 Fail to Produce Impacts

At 1842 and 1843Z, the LJDA signal 7 and 5 sigma jump, respectively, which caused me to take notice (see image #1 below west of “Wayne” county name). On closer inspection, the raw data suggested a movement from 10-13 strikes per minute to near 20, then into the lower 30s over those 2 minutes. A radar image is also included from the case depicting the storm collapsing and never producing significant weather. Reflectivity data was unremarkable and ProbSevere remained in the 30s. No action was taken by the warning operator.

Is it worth using total strikes as a background filter when STD values are so small, and total strikes are < 20, in order to reduce FARs?

Rocky

Nearcast Model Aides in Forecasting Severe End Time

The Nearcast model vertical instability product had cloud/missing data issues, but still was able to provide some good timing on the eastward progression of the front through the Morehead City forecast area. Note the light blue pixel area (unstable), albeit only a small group of pixels, shifting east in the loop below.

This timing can help with severe weather staffing at a forecast office and with DSS messaging to customers.

Rocky

Towering Cu 1 min SRSOR data

The 1-min SRSOR shows a towering cu over the ILM forecast area this afternoon. Out of all the scattered showers/thunderstorms, the 1 minute data easily shows which thunderstorm is rapidly growing. The KLTX radar data confirmed by 50 dbz up to 28 kft. The lead time by the SRSOR was probably 5 to 10 minutes ahead of the radar data.