Week 2 summary and comment round up

As week 2 comes to a close 11 May 2018, we review the comments from our final debrief below. Much of this echos the discovery and opinions from throughout the week.


GLM:

• Training remains an important question and consideration.  Would love to have subject-matter expert available locally for all forecasters (may become frustrated by the data and not use it w/o that person).  
• SOO or focal point can be that local subject-matter expert, however, this will demand evolving training exercises.  Move beyond VLAB, work with WDTD to create hands-on and locally-relevant training opportunities.
• Typical order of use this week:  Total Energy (primary), FED (secondary) and Flash Size (tertiary). 
• Limit the amount of data available on first release (only to the three products listed above???); eliminate point-based or centroid products.
• Integrate GLM data with ground-based lightning systems to help understand and alleviate parallax concerns, particularly when issuing a special weather statement or IDSS for lightning.
•  Want to work more cases and focus areas.  E.g., where radar coverage is poor (western US), fire weather, and aviation -- appears that areal extent and pre-Cloud-to-Ground information will be important.  Context is important and will drive various need/demand for individual GLM products.

ProbSevere (all hazards):

• Did not trust the probabilities in all environments this week.
• Did well with hail and if storms were a bit more steady state.
• Seemed to behave worse in western US and with wind threats.
• Liked using the probabilities as trend information for storm intensity, but not necessarily a particular number.
• Would like to see trend graphs not only of probs, but also internal items in algorithm.
• Preferred the individual hazard products (read-out too long on single ProbSevere)
• Some confusion regarding time scale of probability (minutes vs hour)
• ProbTor could be more difficult to understand reasoning for probs than other hazards; Use a lower threshold for ProbTor and adjust color tables accordingly.
• Would like to see "weak" "strong" indicators on more than just glaciation rate. 
• Difficult to pick out differences in storms between 70-100% probs; color table could use more delineation at higher end (all storms appeared pink).
• Could be useful to communicate impact w/public - would remove numbers and use Low - Mod - High for threats.

Convective Initiation (CI) and Severe-CI:

• Not terribly impressed by algorithm:  completely missed some objects, overdone in some areas, underdone in others.  Hard to understand why.
• Can provide situational awareness, does give some indication of development, but algorithm may need modifications to be more useful.
• Suggest either removing probs <30% or moving to transparent (to know algorithm is tracking these storms).  Large blue confetti-areas are distracting.
• Difficult to utilize in environments where noisy and chaotic. 
• Did not understand differences between algorithms (CI and SVR-CI):  why would CI be low and SVR-CI be high? 

All-Sky LAPS:

• Used in pre-convective environment, showed instability and moisture fields and gradients in those well.
• Could use in social media posts to explain the "WHY" behind the forecast.

NUCAPS:

• Data from JPSS integration was new (or relatively new) to most forecasters.
• Development of best-practices, easier menu-access (not buried in volume browser) and quick-guides would be helpful for increased use.
• Earlier access to data is highly important, but also need better visualization options.
• NSHARP options need to be more user-friendly, cumbersome to pull up multiple soundings in different CAVE displays to compare.  Would like to access shear parameters and get box&whisker plots.
• Difficult to evaluate trade-off of no-data available vs model integration into products.  Would like keep separate from LAPS options, but can be difficult to evaluate with gaps in data coverage in gridded products.

MK-Thursday Prob Severe Review &

Mesoscale 1 on RGB Split Water Vapor, toggle to Day Cloud Convection

The RGB Day Cloud Convection image has become my image of choice to enhance my multi-dimensional thinking of the storm environment due to the color bank and the resolution.
Our focus was Raleigh, but since my broadcast DMA combines 3 different WFOs, I looked at the line of storms developing over the western Piedmont/Foothills.

Prob Severe Wind Over RNK Velocity appears to be running hot with only one or two confirmations of a wind report with a tree down in Yadkin County and Henry county VA. There were several reports of pea to Quarter Size Hail with consistent quarter size hail reports as the storm progressed to the ENE out of the RNK area form Mount Airy into VA. 4 Panel evolution shows a lower percentage of hail possibility of 10 percent after it has already verified hail and then a higher wind prob of about 50% without verification at 19:12 Z.


 Prob Severe Wind Over RNK Velocity  with only one confirmation of a wind report with a tree down in Henry county..., several reports of pea to Quarter Size Hail from Mount Airy into VA. 4 Panel evolution shows a lower percentage of hail possibility of 10 percent after it has already verified hail and then a higher wind prob of about 50% without verification at 19:12 Z.

 This trend is clear as well with the pulse thunderstorm that drops golf ball size hail at 21:25z as seen by this series of 4 panels.

 Notice by adding GLM Total energy here this appears to be a better indicator of storm intensity if not type of severe storms. Typically in this region from a historical perspective using ENI data combined with reflectivity, this is an excellent predictor and indicator of severe hail along with storm heights, and watching developing 'hail' tracks as provided by WSI which is the shear tracks as we track the storms.  Granted, this is a messier presentation than many would like, but I find it interesting that this type of layer comparison with GLM and reflectivity/velocity may be a better indicator of storm intensification than the current ProbSevereProduct. At this time, I would rarely imagine using the ProbSevereAll Product alone and would likely never choose percentages. Hearst Television Meteorologists are using a scale from None, Low, Moderate, High to describe the type of severe impact. The more details we can convey will be helpful as we still hear our viewers in large numbers comment that they were unaware a tornado was possible with "those storms."

For a verification of the ProbWind increase (catch-up) I chose the velocity in a single panel. The Northern section of the storm pushing into Henry County does eventually verify with trained spotter reports of trees down, but most reports are quarter size hail. 

This RGB and ProbModel shows still after verification at the surface the hail model hasn't been responsive-only to 10-20% Prob.

Watching developing storms from GSP to RAH warning area with Severe Prob Hail overlaying the RGB Day Cloud Convection Product.
Severe Prob 4Panel at 22:24Z just before the golf ball size hail /wind reports with lower left panel indicating low level rotation in yellow, blue  hail tracks & GLM in right panel shows higher total Energy growing North. ProbWind Model is performing poorly still as a forecast tool as storm reports verify wind damage & possible microburst indicated.

 Below I used RGB images and a combination of All-Sky Lap like CAPE and Simple Water Vapor in the RGB allow for some gradient perspectives with layering shear tracks and GLM to continue monitoring storm growth and possible intensification that the GLM often seems to match.

 

MK

 

CI and Severe CI in northern Nebraska

CI and Severe CI worked better today across northern NE highlighting areas of initiation and potential for severe.

- Jack Swigert

New NUCAPS procedures for HWT...

So, after a few days of discussion and observation, we've revised the NUCAPS sounding Procedure set for HWT.  Here is a short description of the procedures and the reasoning behind each one.  Whenever we refer to NUCAPS soundings, we're referring to the NUCAPS Improved Latency Soundings, with the exception of one procedure that contains the modified soundings.  Example pics of each are included at the bottom. 

Procedure 1.  NUCAPS Soundings & 850 MB Theat-E, GOES-16 Vis (0.64um)

Forecasters need some context for the NUCAPS soundings, so you will see in this procedure and all of the rest (with the exception of one) the inclusion of some form of GOES-16 ABI imagery with the NUCAPS sounding locations.  It's important to know why "holes" appear in the gridded data or why soundings are coded as yellow or red.  The presence of clouds helps to provide the necessary context here.  This procedure includes a simple visible image (0.64 um), but we also included 850 mb theta-e.  Theta-e can include valuable information about the location of frontal boundaries, and can indicate locations for locally higher instability in some pre-convective environments.

Procedure 2.  NUCAPS 850-500 MB Lapse Rate, GOES-16 0.64um and 10.3um

Here, we include NUCAPS soundings along with gridded NUCAPS 850-500 MB Lapse Rate data.  We also include the GOES-16 visible (0.64 um) and the 10.3 um IR "sandwich" product.  The lapse rates seemed appropriate to include with the sandwich product since the inclusion of the IR can also relate something about cooling cloud tops in areas of strong elevated instability or steep lapse rates.

Procedure 3.  NUCAPS Soundings & 850-500 MB Lapse Rates, GOES-16 Vis (0.64um), and MRMS Refl at -10C

Here, is the same as the last, except...we leave out the IR imagery and include MRMS reflectivity at -10C.  Why -10C?  Well, it's the beginning of the mixed phase region, potentially useful for lightning production, showing signs of early convection.  The -10C layer also usually falls somewhere within the 850-500 MB layer.  Ok, closer to 500 mb probably...but well...we had to choose something.

Procedure 4.  NUCAPS Soundings & 400-200 MB RH, GOES-16 Vis (0.64um) and 6.2 um Water Vapor

In this procedure, we include the gridded NUCAPS 400-200 MB RH, along with visible and imagery from the upper-level water vapor band (6.2 um).  We chose 400-200 MB RH since this vertical region corresponds generally well with the weighting function for the 6.2 um band.  We include the visible channel again (although it is layered under the WV channel) for sounding context.

Procedure 5.  NUCAPS Soundings & 850-300 MB RH, GOES-16 Vis (0.64um) and 7.3 um Water Vapor

For this procedure, we employed the same reasoning as above, including the 850-300 MB RH since the weighting function for 7.3 um is rather wide, encompassing this vertical region.  It could probably be argued that this should be narrowed a bit, but AWIPS only allows for specific vertical pressure layers.  This seemed the most appropriate at the time.

Procedure 6.  NUCAPS Modified Soundings & 850-500 MB Lapse Rates, GOES-16 Vis (0.64um)

This procedure contains the modified NUCAPS soundings along with visible imagery and 850-500 MB lapse rates.  We includes these lapse rates since these layers generally offer good retrievals for NUCAPS, and not boundary layer, which is modified in these soundings anyway.  Also, forecasters have suggested it may be good to have other data which would help to identify soundings that are in areas of potentially greater instability.

Procedure 7.  4Panel - 850-500 & 700-500 MB Lapse Rates, NUCAPS/HRRR/GFS20/NAM40

Here, we offer a simple comparison of NUCAPS gridded data with some numerical model data.  In this case, the HRRR, NAM, and GFS.  Of course, there are certainly other comparisons possible, but we wanted to keep it simple at first.  However, please feel free to offer other suggestions!

As promised, here are some sample snapshots of the procedures...

Procedure 1.

 

Procedure 2.

Procedure 3.

Procedure 4.

Procedure 5.

Procedure 6.

Procedure 7.

-Kris and Nadia

CWA TomClemmons RAH 05-10-2018

Synopsis: Well removed from the better upper dynamics/forcing and shear
that will move through the NE US this afternoon and evening,
forcing across central NC will be rather weak, limited to mainly
weak near sfc convergence, as the surface trough crosses the area.
However, strong daytime heating, featuring afternoon temps in the
mid 80s, will result in steep low-level lapse rates. These steep low-
level rates when coupled with with BL dewpoints in the lower 60s,
will fuel moderate instability of 1500-2000 J/Kg that extends well
into the mixed phased region. Despite the deep westerly flow in
place, majority of the CAMS indicate a fairly congealed multi-cell
line segment crossing the area between 18z to 03z. Given 20 to 25
kts of deep layer shear, some of the strongest updrafts will have
the potential to produce severe weather, including, hail and
damaging wind gusts.

Hampered by slow computer systems Tuesday, Wednesday, and Thursday:(

Notice low correlation between  -20 C Isothermal Reflectivity & GLM Total Energy 5min-1min update. Notice storm near the cursor.

In this example the storm is on the northern RAH CWA border, the updraft has pushed 50-60dbz echoes up through the -20 C isotherm, notice this time the GLM Total Energy and the Extent Density (# of Flashes that have crossed a pixel) are both showing high values. This would be a good situation awareness tool during an ongoing severe weather event. This storm was currently producing damaging hail and strong winds.

ProbSevere Wind and Hail:

1.75" hail was reported at 5:25 pm near Bahama.

ProbWind:

3NW of Stovall 2 Trees Down

ProbTor for NE Storms

The evolution of thunderstorms across Nebraska featured many storm splits and mergers and convoluted velocity data. Storms across northern NE north of the warm front exhibited some modest rotation aloft but cells further south across the panhandle into central NE displayed more impressive rotation. ProbTor hit these southern storms with higher values in the 20-30% range with lower values across the north, although the leading storm in central Cherry county had some higher ProbTor values near 20%

- Jack Swigert

Supercell Merger VIA VIS/IR Toggle

Saw this VIS/IR Toggle with the supercells merging across Garden, Sheridan, and Cherry Counties in Nebraska. The coldest cores at the end of the animation are in the eastern portion of Sheridian where the main two supercells merged. Had Prob East on the image and did see where it was showing probabilities of cells along the forward flank could develop.

Supercell

Supercell Merger in NE using ProbTools/GLM

Noticed an issue with all of the Prob products when two supercells merged. Captured an animation, but the probability products merge into one big area and is unable to resolve the individual updrafts as the transition is occurring.

Also, noticed that the GLM Flash Density and Total Energy increased markedly as the merger took place. With all of these updrafts so close together, am also seeing a marked increase in Average Flash Area-especially over Grant/Cherry counties.

Supercell

GLM increased after supercell Split

Noticed that GLM flash density and total energy spiked after the supercells split over Garden County Nebraska. Take a look at the GLM and also the MRMS/Prob Severe loops. Tried to add more images to these loops to look at the progression from where it was in Cheyenne county.

I am not really sure if there is a correlation with the increase in the particular GLM parameters, but did notice the increase after the storm split. Also take a look at the storm over Morrill County where flash density and Total Energy spiked in values. Average flash area is also increasing in between all of these cells showing large flashes.

More to come...

Supercell

GLM offset with ltg jump

GLM overlaid with ENTLN data showing GLM offset to the northwest of the storm.  Ltg jump occurred over the few previous frames as storm seemed to cycle again, with dBZ nearing 75

Splitting of Supercells RGB Satellite Imagery

Here's some awesome satellite imagery from the splitting supercell from Garden County Nebraska off the Day Cloud Convection RGB.

More to come...

Supercell

Splitting of Supercells and Prob Severe/Tor/Wind

A supercell that had been warned on split with the northern storm moving into the more favorable area of instability and the updraft rapidly strengthened to severe. Noticed that Prob Tor has increased to 9% on the northern storm and Prob Hail/Wind are 99%/89% respectively.  Issued a severe thunderstorm warning shortly after the last scan on this animation. Will be monitoring that northern storm for ProbTor. Have seen some upstream storms with strengthening with rotation.

More to come...

Supercell

GLM spikes for northern NE storms

Tracking northern NE storms, we could see the GLM spikes on rapidly strengthening thunderstorms across Sheridan and Cherry counties in north-central part of the state. These storms are exhibiting strong hail and wind signals and golf ball sized hail was reported by the public. Interestingly enough, while the initial spikes were impressive, the storms further south and west (south of the warm front) seem to have a higher GLM total energy and density overall and for a longer duration.

- Jack Swigert

Noticeable increase in GLM lightning detection

Noticed a marked increase in Flash Density, Total Energy, and Average Flash Area as the storm strengthened over Garden County Nebraska (same storm from earlier blog posts where warning was issued). Included an animation of the GLM data along with ENTLN and NLDN to calibrate my thinking a bit.

On the average flash area notice the large flash stretching across Cheyenne and Deuel counties in Nebraska.

More to come...

Supercell

Severe Storm with All Sky CAPE Prob Severe

Interrogated a storm entering the gradient in instability shown by the All Sky CAPE products and also increasing Prob Hail and Wind Products (cell with SVR box on it). The cell is moving into Garden County Nebraska:

More to come...

Supercell

Severe storm exhibiting almost no ltg

Severe storm in north Nebraska (Z shown)

GLM 4 panel (FED,Area,Total energy) showing almost no lightning activity

ProbSevereWindTor with severe storm

Looked at Prob Severe Tor/Wind/Hail with MRMS reflectivity. The Hail probabilities actually increased to 90% prior to warning issuance. MESH values were around 1.56 inches. Prob Wind was a lower (78%) value. Did see where there was a TBSS in the dual pol and reflectivity products indicative of hail. Issued severe thunderstorm warning shortly after the probs showed this. Did notice that Prob Tor was around 1% but monitoring the velocities as the cell is located near the warm front and wind shear is sufficient to support it.

More to come...

Supercell

NUCAPS vs LAPS Discrepancies

ALL SKY LAPS showing around 1600 CAPE (not sure what CAPE is being computed? ML,MU,SB?)

One green point selected from NUCAPS showing 3200 SB and 2200 ML CAPE, much higher than ALL SKY, but SFC DP and Temp match METAR obs showin in figure 1

CAPE much more in line with what SKY LAPS is showing, but Temp (DP) seem to be higher (lower)

North Platte 20Z Special Launch vs 20Z NUCAPS

Just doing a quick comparison between 20Z NUCAPS modified sounding near North Platte (green dot southeast) to 20Z Special RAOB launch from North Platte.

NUCAPS 20Z                                              KLBF 20Z

Overall, it picked up the genaral temp and dewpoint profiles fairly well, but there were a few noticeable differences. NUCAPS failed to pick up on the elevated mix layer that the KLBF sounding did. NUCAPS therefore had a weaker capping inversion and a lower freezing level. KLBF had a drier mid-level.

- Jack Swigert

No To Low CI and Storm Initiation

Noticed that a cell (circled on image) over northeastern Wyoming did not have any severe CI, low CI (17%) before it initiated. Not sure what may be happening with the algorithm. There was no cirrus canopy around the cell other than other convective initiation (south) and clear air (north).  Included the beginning image:

Here is the last image I took of the storm:

You can see that it has a strong updraft (via IR Satellite). I do not have severe CI displayed but it had no values in around that particular cell. With it moving towards a gradient in instability, could see it strengthen further soon.

More to come...

Supercell

Severe CI Product hinting at initiation in northern Nebraska throughout the early afternoon

northern Nebraska convective initiation after severe CI hinted in that region with high percentages (although jumpy) all throughout the early afternoon.

All Sky Products Environment Analysis

Utilized the All Sky CAPE and Precipitable H2O products compared to the HRRR data. Could definitely see the All Sky CAPE is showing a good gradient close to where storms are already developing and have gone severe near CYS radar. Note: The severity of the storms is not shown in the radar. It was included in this image mainly as a frame of reference where cells started to develop. Later volume scans showed much more organized updrafts.

Would expect these cells to continue to strengthen or maintain their strength as they head eastward across the gradient.

More to come...

Supercell