Late December storms

A negatively-tilted shortwave brought some low-level moisture return to the gulf states this week, and with the moisture, some scattered severe storms.

A couple tornadic storms affected portions of east Texas. The NOAA/CIMSS ProbSevere model now incorporates the GOES-16 satellite growth rates, and a storm affecting Cherokee Co., TX, had a strong normalized growth well before it produced severe weather.

Figure 1: AWIPS2 screen captures of MRMS MergedReflectivity, ProbSevere contours, and NWS warnings for a storm near Rusk, Texas.

The ProbWind values vacillated largely between 50% and 75% for this storm, before producing a tornado at 00:56 UTC and multiple wind damage reports in the town or Rusk, TX. The strong GOES-16 vertical growth rate, large ENI flash rate (~30-70 fl/min), and stout kinematic fields (eff. bulk shear ~ 45-50 kts; meanwind 700-900mb ~ 35 kts) combined to produce these moderate-strong ProbWind values. The MRMS MESH remained rather low (~ 0.2 - 0.6 in), signaling that this was not a severe hail situation. ProbTor had a maximum value of 12% before the first tornado report.

This storm featured jumps in ProbWind value (one produced by a large increase in flash rate, indicative of a lightning jump), and being an outlier storm amongst its neighbors, in terms of probability value. Both features in ProbSevere objects have been identified by forecasters as indicating possible severe weather.

A second storm formed further south and later in the night, which also produced a damaging tornado, touching down northeast of Beaumont, TX, and later northwest of Lake Charles, LA, blowing off the roof to a restaurant.

Figure 2: AWIPS2 screen captures of MRMS MergedReflectivity, ProbSevere contours, and NWS warnings for storm heading into southwest Louisiana.

The kinematics for this storm were very favorable, with effective bulk shear of 50 kts, meanwind 700-900mb of 45 kts, and 0-1 km storm-relative helicity near 300 J/kg. The first tornado touched down at 07:41 UTC, when ProbTor was about 30%. ProbTor then jumped from 30% to 50% at 08:00 UTC, the time of the second tornado report. This jump in ProbTor value was coincident with an increase in total lightning (a lightning jump) as well as an increase in low-level rotation.

Figure 3: Time series of ProbTor and predictor values for this storm affecting southeast TX and southwest LA.

A tornado warning was issued at 08:10 UTC, when ProbTor had just increased to 90%. The third tornado reported, at 08:20 UTC, was rated EF1 and destroyed the roof of a restaurant in DeQuincy, Louisiana.

Spartanburg, SC Tornadoes

A potent October shortwave traversed the southern U.S. on October 23rd, bringing with it a round of severe weather to the Southeast U.S. The Storm Prediction Center outlook had a 5% contour for tornadoes (Figure 1; probability of a tornado within 25 miles of a given point), citing very strong low-level shear and weak to moderate buoyancy.

Fig.1: SPC tornado outlook issued at 16Z 10/23/2017.

Convection took on a linear storm mode in South Carolina, with a surge in a line heading toward Spartanburg (Figure 2). The NOAA/CIMSS ProbTor model increased to over 80% by 18:20Z, owing to increases in low and mid level azimuthal shear, and a jump in total lightning density, while residing in an environment with excellent 0-1km storm relative helicity (Figure 3).

Fig. 2: ProbSevere (all hazards) contours, NWS warnings, MRMS MergedReflectivity, GOES visible reflectance. The ProbTor was the highest hazard probability for this storm; 88% at this time. 

The first tornado reported was at 18:54Z, coincident with the first NWS tornado warning. The first tornado damaged permanent and mobile homes, downed power lines, and destroyed a horse barn. Later, the storm produced another tornado between downtown Spartanburg and I-26, snapping large trees, as ProbTor was about 45%. After dropping below 20%, ProbTor again increased to 40% at 19:36Z, when another tornado was reported near the North/South Carolina border.

Fig. 3: Time series of ProbTor (thick red line), with constituent predictors. NWS warnings and preliminary LSR reports are on bottom axes.

In this case, ProbTor may have been able to provide an earlier "heads up" to forecasters monitoring the storms for potential tornadic activity. ProbTor is best utilized in conjunction with current warning practices and interrogation of base radar data. If a velocity couplet is outside of the ProbTor object polygon, ProbTor will be underestimated, as may have been the case for a second tornadic storm in North Carolina on this day.

2017 Experiment Complete

The 2017 GOES-R/JPSS Experiment in the HWT is wrapping up today. This has been a great experiment this year with getting to utilize live GOES-16 data in operations here in the testbed. Also we were able to demonstrate GLM lightning data to forecasters for the very first time and have gotten a lot of valuable feedback from forecasters on what they would like to see operationally form the GLM in terms of display capabilities. Feedback from the fourth and final week of the experiment is posted below:

GLM

Get the parallax fixed before fielding

Forecasters will be confused between events, groups, and flashes and what each means and why they are useful

The Stano color curve would be the best default

Being able to monitor trends would be the most useful

A pop up time series like a pop up skew t could be very useful

Training seemed to be pretty good for preparing people

Seeing the spatial extent is a very useful quality of GLM

Another big utility is for monitoring electrification before the other networks can

Don’t see people using it too much if the parallax displacement is still an issue when fielded

NUCAPS

Useful information yesterday out of the gridded products when there was clearing in the area

Obviously most useful for pre-convective environment and getting an early afternoon pass over the area

Overall the experimental product seemed more useful, but there were times that the operational seemed to be a better representation of the environment.

The yellow dots seemed to be somewhat reasonable at times and can have some useful information

As long as people understand how the modifications in the experimental profile are made, they can be extremely useful

Like having both the experimental and the operational soundings to compare the atmospheres

Repeating the latency problem which is the biggest hurdle to operational use

Would be nice to be able to have some automated products produced from NUCAPS profiles

ABI

Understand the RGBs a lot better now than before

Found a couple really useful ones for operations

There were some very useful RGBs for convective applications

RGBs seem to bog systems down in some offices when trying to load

Training should concentrate on best practices and what the colors mean for application

Training needs to be heavily focused on operational benefits

Daytime Cloud Phase RGB seemed to be one that should be introduced first, especially this time of year for convective development

CAPE is still a problem, being consistently too low

Derived Winds should be color coded by pressure level instead of wind speed and steering clear reg, green, yellow type color combinations

ProbSevere

Useful for situational awareness

Good tool for monitoring trends and keeping an eye on storms of interest

ProbTor was useful for seeing storms that were different from any of the other storms

ProbHail was more restrained and seemed to reduce FAR from being too high from relying solely on MESH

Still struggles with wind events and tracking of linear features

-Michael Bowlan

GOES-R Liaison at SPC/HWT

Storms came into NW SD, barely

-tvguy

Line of storms were weaker on the southern half of the line coming in from MT... even though environment indicated some strengthening should occur. Due to 60 dbZ reflectivity at 15Kft, and increase in velocities >30 kt issued SVR for extreme NW corner of Harding Co for low end wind, hail threat. ProbSevere was not impressed, with 11% hail and 9% hail. But I'm not sure this tells the whole story, given strength of storms to the north and potential development of outflow winds as well as elevated reflectivities suggested a greater hail threat than advertised. Chose to discount the negativity of ProbSevere, with additional concern about data quality at such a long distance from the UDX 88D.

As warning about to expire, received LSR of 50 mph. Non-severe. But then velocities really picked up along the line, up to +57 kts. Due to strenthening, reissued along the line for much of that county (Harding).

Even though ProbSevere values were very low... under 10% on all parameters... the storm did produce highway sensor value of 62 mph. Kind of thinking the ProbSevere object is created by reflectivity core, but doesn't consider the stronger wind values created out ahead of that storm -- or, perhaps there are latency issues due to data processing. I don't know.

Finally, saw convergence signature (64 kts) on southern part of line. Upon expiration, reissued farther to the SE for line of windmakers.

ND 1 min imagery

Can see what looks to be lower level inflow into the main area of severe thunderstorms. This indicates to us that the storm is maintaining intensity. This, along with radar and PROBSevere data has led us to continue our warnings

Missing gridded NUCAPS data in complex terrain?

I noticed there were a lot of mixing pixels in the NUCAPS gridded data over the Black Hills despite the fact there was no notable cloud cover. Expanding west, it became apparent this was a common theme across Western Montana into central Idaho as well. Sounding availability overlays show most of these area are considered yellow. It seemed many of these points were areas where there was a gradient between darker forested areas in the terrain, and lower adjacent valley locations. For locations in the west, for this data to be useful and for us to have confidence in using it, we really need a more complete data set. A sounding from the Black Hill is shown at the bottom, which seems meteorologically reasonable.

-64BoggsLites

ND Convection along Warm Front

Finally have CI across the western portion of the CWA. Forcing is largely along the warm frontal boundary at this time, with two notable cells. Still monitoring the potential for initiation along the dryline. Have opted to continue the warning on the cell mentioned in the previous post given a combination of radar, satellite, and environmental data. 1 minute imagery is now in for the area: seeing near steady thick ice in the clouds associated with the isolated cells (which includes the warned cell), but not really beginning to see the cu along the dryline becoming more agitated.

2045Z UNR update - satellite and lightning trends

...update....the cell to the north did in fact product a CG strike per ENTLN data approximately 5-10 minutes after flashes/events where first noted in GLM data.

previous post...

The activity working across south central MT associated with a 500mb speed maxima has continued to develop eastward. Day cloud phase shows an increase in cumulus over far southeast MT over the last hour, and this activity has slowly increased in depth. Meanwhile the cluster of showers just to the west is producing a thicker anvil layer

The Sandwich display shows gradually cooling cloud tops indicating the convective cluster continues to slowly strengthen as it moves into a somewhat more favorable environment.

A 4-panel lightning display shows an increase in lightning trends as well. What's interesting to note (aside from the general increase in lightning trends) is the top left panel is a few flashes and events in a shower to the north of the better convection...an area where cloud to ground lightning has yet to be noted, and max dBz is near 30. Perhaps an indication this cell is strengthening and could produce lightning in the next few minutes.

-64BoggsLites.

Monitering convection along dryline

While storms are initiating near front, have been watching along dry line for new storm development. While that has not yet occurred, did catch a failed attempt at initation.  Visible loop (below) indicates what looks like an orphan anvil develop along the dry line.

In addition, daytime cloud RGB also showed that glaciation started (color becoming more green), it never grew past that initial color and diminished quickly.

-JRM

Bismark WVR

Issued a severe thunderstorm warning for large hail and damaging wind on a storm moving into the CWA from the west. Saw rapid cooling in the 5 minute Day Cloud Phase and the Sandwich imagery. An overlay of PROBSevere showed an increase in ProbHail from about 50% to 90% as the cloud tops cooled. All tilt radar display also confirmed these observations by showing 60dbZ over 30,000ft. Will now be able to monitor 1 min imagery.

Forecast Update - Bismarck CWA

Currently watching developing cumulus field behind first area of convection along and east-west oriented stationary front near Montana/South Dakota border.

Daytime microphysics RGB indicating glaciation taking place in this area and with GOES-16 derived Lifted Indexes suggesting this area most unstable would expect storm growth to continue. Intensity of storms further east in line with previous stability analysis as storms appear to be moving into less favorable environment.

A fairly rapid glaciation  of the storm was noted between 1927 UTC and 1957 UTC.

 -JRM

GLM: Visualization

Noticed when looking at gridded GLM data (8km - 5min data/1 min update), had trouble quickly picking out area of high activity.  Given activity wasn't too intense, seemed that activity was a bit muted.

 Opted to go create a rough custom color scheme using warm colors to be able to contrast more against a visible satellite image. Wasn't too concerned with the actual amounts of flash occurring, but mainly trends in relation to other cells. Mainly another SA tool to quickly discern potential problem areas. --Tahoe

Combine 1 min VIS and lgt

This loop shows a combination of 1 min VIS data overlayed with 1 min GLM flashes. This may be a good DSS tool or a way to track lightning trends. -ams

Anvil GLM events.

GLM Events 5 minutes old to new over National mosaic radar.

Benjamin

GLM vs land based networks

GLM is providing some great added value to the other earth based networks. When playing around with the color tables you can really pick up on the peak areas a tad better.

A quick look at NUCAPS gridded data.

First chance to take a look at gridded NUCAPS data. Comparing the 700mb and 500mb NUCAPS grids to RAP and HRRR analysis, the NUCAPS was consistently about 2 degrees C colder at 700mb, and 1-2C colder at 500mb. This is also evident in the H7-5 lapse rate image below, with NUCAPS in the top left, then clockwise HRRR, NAM40, and GFS20.

-64BoggsLites

Bismark CWA Derived Wind Analysis

Quick look at the derived wind fields across Bismarck CWA. Still a lot of clear skies, but sum information can be gleaned from image below (upper left 300mb, upper right 500mb, lower left 700mb):

Think lack of elements to track at the moment have lowered my confidence in some of the values, but in areas with  more extensive cloud cover seems to be picking up jet at 300mb.  Think best track to take is to monitor how these fields change over time as tracking elements begin to increase.

One concern I have is the color and labeling scheme. The current default is the same as VWP where red corresponds to poor data quality and green is good. This could be fairly confusing. Instead of coloring by speed, perhaps coloring by pressure level would be better?  As it stands you could not overlay several layers over an image and use it easily.


-JRM

RAP pre-storm

-tvguy

Looked at GOES total PW. Amounts >1" from eastern UNR CWA into western ND and far eastern Montana... pretty decent for this area. Unfortunately, the surface obs are still pretty dry in the western Dakotas, with dew points only in the 50s - for now - though there is a southerly wind for most everybody.

NUCAPS total totals were uniformly 50-59 north of Rapid City to the Canadian border.

Looked at cloud optical depth to get some idea about the thickness of the cloud cover in the central CWA. Appears to show cloud cover is thin, so I assume we should get strong solar heating this afternoon.

By 21Z Cu field approaching NW corner of SD. Queried recent NUCAPS grids to check 700 mb temps, which were 12-14C.

At this time, SPC issued t-storm watch for NW corner of SD, but mostly for western ND.


But also looked at NUCAPs 850 Lapse rate... over 8C/km. Expect that if these towers in western MT move into that area, they should blow up pretty quickly.
1 min VIS puts storms approaching NW corner... with 1 min GLM flash points increasing quickly.

When looked at same flash data, they was well out ahead of the main line of storms on radar.

Bismark CWA - Derived Stability/Moisture Data Analysis

Quick look at some of the derived parameters sat 1857 UTC prior to expected storm initiation today.  Following image has the following parameters from upper left to lower right : Total Precipitable Water, CAPE, K-Index, Lifted Index.

TPW fields indicate some moisture pooling to the west of ongoing convection, with a similar trend in the instability fields. Drier, more stable air in place upstream of developing storms. Unsure if this just indicates where current forcing/ascent is and this will translate eastward or if current storms moving into less favorable environment.

CAPE values continue to be significantly lower than numerical model analysis, but LI values much closer and seem reasonable given the pattern.

-JRM

UNR Satellite Analysis

A loop of upper, mid, and lower level water vapor along with a simple water vapor RGP indicates an area of potential lift crossing south central MT (top right). The RAP indicates a 50kt 500mb wind maxima lifting through this area, and GOES-derived winds suggest the core of this wind maxima may be displaced a bit further north and east in the model. The wind barbs do seem to drop in and out with each frame. Not sure if this is a sampling issue or what.

Visible imagery (not shown - CAVE is locked up) shows an area of convection over south central MT associated with this jet streak, and the day cloud phase RGB indicates this area has become glaciated.

Anticipate this activity will continue, and likely grow in strength as it moves into deeper moisture further east.

-64BoggsLites

Bismark Early Phase Convection

The RGB Day Cloud Phase is indicating some vertical development/introduction to some cloud glaciation across western ND. Would expect this to be associated with some shower development, which when pulling up the MRMS data there is evidence of a slight increase in shower activity. This color scale is much better than the eye piercing red and green. I might prefer this imagery over the clean IR window product that I've been using all week to monitor cloud top cooling.

Week 4 Day 4 Operations

Forecasters today will wrap up the week operating in the Bismark, ND and Rapid City, SD CWAs.

-Michael

Day 3 Wrap Up and Feedback

Day 3 saw forecasters operate in the Melbourne, Fl CWA all day monitoring some weak sea breeze convection, and in the Sioux Falls, SD CWA monitoring an initial MCS and later some strong storms forming off of the remnant outflow boundary. Discussion feedback is posted below:

GLM

Seeing the anvil lightning was really cool to see how far the extent of lightning can be from the parent storm

Saw GLM flashes and NLDN CG flashes ~90 miles from storm core

In Florida it was easier analyzing the storms using the flashes to keep the storms separate from each other

Looked at different grid resolutions and the 9 - 10 km resolution seemed to work best

5 km resolution was to “pinpointy”

Events made the most sense to use over groups

Liked the Stano test color curves as the easiest to look at quickly and pick up the trends and hot spots

Parallax issue would probably be a big issue in the field

First impression is a big deal, and the parallax issues should be fixed before fielded in the offices

Much rather have the GLM combined and color curves here to use in the field, it’s much more intuitive

NUCAPS

No gridded data in Florida

Sounding were a lot better representation of the atmosphere yesterday than previous days

Showed a bit of a weaker cap in the gridded data than the RAP and the cap did end up breaking shortly after

Very useful for initiation yesterday

Having more passes the better, especially in the early afternoon time frame

Soundings are consistently doing pretty well above the boundary layer

Like having the option for both the operational and the experimental soundings depending on the boundary layer environment

ABI

“I like it”

Monitoring for initiation was nice for monitoring for glaciation

Cumulus field turning to stratocumulus showed a capped environment

Day cloud phase RGB shows glaciation really well

Used the 3.9 yesterday to pick up some thermal difference

Obviously not all bands are going to be used by themselves

None of the other bands really jumped out too much with the pulse convection

Low-levels of derived winds have very little information

ProbSevere

A couple of large ProbHails in Florida that seemed a little unreasonable for the tropical environment it was in

ProbTor highlighted the part of the bow that was most intense and capable of tornado production

It highlighted the part of the line that was different

Some of the tracking, especially on lines needs some work to be useful in line events

Overall it’s a great tool that seems ready to be used in operations especially as a SA tool

It forces you to really interrogate the storms of interest to see what is going on

Helpful for people with lower radar experience to fall back on for interrogation

-Michael

Another Anvil Lightning Event - Near Akron Iowa

GLM picked up another case of anvil lightning at 2341 Z near Akron Iowa.  CG occurred at same time as GLM events were noted, so no real lead time to this strike was observed. Image below of accumulated 5 minute GLM event density and flash data updated every minute along with the NLDN CG strikes.

For reference this image indicates how far the main area of storms was from lightning strike (white dot). There were some 30 dbz echoes near Vermilion SD but they never grew much stronger than that during this period. This was around 90 miles from main storm area.

-JRM

Anvil Lightning-Near Yankton

Interesting to see a cloud to ground lightning strike occur well away from main updraft cores in area with little if any meaningful reflectivity. Following loop is focused on the Yankton area, well removed from the main cells of thunderstorms. Image is a combination of GLM  5 minute accumulated event density and MRMS 1 km composite reflectivity.

A couple of things stood out to me. First you see the area of GLM areas of GLM events extending over the area followed by a few flashes, followed by a NLDN positive strike southwest of Yankton.  The following image shows how far away that was from main core of storm. White dot represents location of positive cloud to ground strike.

-tvguy/jrm

JAX Pulse Storm

In the JAX CWA, a storm seemed to intensify along a shear zone which was detected well in the upper level water vapor imagery. The intensification was noted mostly via rapid cooling of the cloud top temperatures seen in the IR imagery as well as the 1 min update of the GLM flash density at 8km. I forgot to load the PROBSevere before saving this image, but PROBhail did increase to 30% for a scan or two (which was very good for us today)

Advancing Outflow Boundary - FSD area

Following loop indicates what appears to outflow from earlier MCS advancing to the south across southern portion of the CWA. Interesting to see it interact with area of cumulus. Can see cu field increase as feature passes. Also gives some indication of overall stability as clouds seem to form into more of a stratocumulus deck with no deep vertical development observed. Increased resolution made it much easier to see reaction to this forcing.

JRM