Slight Risk West and East

Operating across the CONUS today with one team of forecasters located in Idaho/Montana in MSO and the other in Illinois (ILX).  The forecasters have also been encouraged to investigate the environments nearby their official CWAs including the ongoing MCS currently crossing the Chicago CWA.

SPC Day 1 outlook for 16 May 2019

For those in Illinois, the environment remains supportive of development  off of outflows from the ongoing MCS or other possible convection.   Though it remains likely that the MCS will continue to remain strong and pose  a threat for strong winds at least across the NE section of the CWA.

All Sky LAP CAPE

For Idaho, it currently remains rather calm, but the CAMS have consistently latched onto expected convection later in the day including supercell storms.

Sandwich IR/VIS product for Western United States

-Kristin

Pinwheel Fronts In The Dakotas

Mid afternoon into early evening saw a bretty good bloom of supercells along a SSW-NNE Cold Fronf in North Dakota...


Thru the period the SVRProb and SVRtor seemed to regularly over warn during this outbreak, BUT SVRHail was spot on, a little False Alarm-y, but it sure didn't miss the Large Hail reports, with %s >90 both instances.  The RGB Day Convection GOES product seemed to respond pretty well with the hail instances as well.



Afternoon NUCAPS over forecast the CAPEs by ~ 500, PW by 0.2", did well with the Downrush temp and DCAPE tho.

Above Anvil Cirrus Plumes and GLM

This post will ask more questions than make assertions :) We currently see evidence of a weak above anvil cirrus plume (AACP) based on the GOES-16 Sandwich RGB (upper left) and CH02 visible (upper right). Total Optical Energy from GOES-16 (GOES-17) is plotted on the lower left (right).  For reference, three of the four frames have 5 minute ENTLN data.



I've wondered if an AACP could extinguish a significant amount of Total Optical Energy (TOE) if lightning was occurring underneath. There are too many caveats here to draw any conclusions, such as:

1. Extreme viewing angle for both GOES satellites resulting in significant parallax.
2. A large viewing component of the sides (instead of just the tops) of the storms, resulting in possibly large and highly variable reflectances that might be harder to calibrate TOE against.
3. Uncertainty regarding ENTLN efficiency and accuracy this far at the fringe of the ground network.

So, with all of that being said, what we see here is interesting. ENTLN does show two areas of lightning. GOES-16 picks up on the western area but not the area under the plume (at least not at first). GOES-17, on the other hand, has a better grasp  on there being two areas throughout.
I hypothesize that GOES-16 is struggling more in this particular scene because of the large reflectance and possible forward scattering issues that GOES-17 is not as susceptible to at this particular time of day.

Again, this is not a great setting to test any hypothesis about how much an AACP is able to throw a blanket over GLM detections. However, I'm confident that next week will provide many opportunities to test this with extremely stout AACPs at far more optimal latitudes.

#MarfaFront

NUCAPS and AllSky Helpful in BIS

NUCAPS and AllSky both were helpful in tracking the afternoon destabilization over North Dakota today. Both data sources provided what seemed to be fairly accurate assessments of CAPE values. Clear sky and GFS retrievals in AllSky were similar, with the clear sky retrievals very closely matching the NUCAPS retrievals. Having a plan view depiction in AllSky was very helpful when combined with RAP shear vectors in accessing afternoon storm potential.



NUCAPS Sounding:


-- warmbias --

Prob Severe - Unrealistically High ProbTor

ProbTor started giving unrealistically high values in northern ND, noting very high Az Shear Values. This appears to be a problem with data QC in the operational MRMS data, as it does not appear in the Testbed data.



Looking at the time series for one of these anomalous Prob Tor values, its clear the bad Az Shear data is contributing to the jump in Prob Tor:

ProbTor Gets Schooled Again

We continue to see significant issues with ProbTor that seems directly related to inflated Low Level AzShear values. This is likely due to an outflow boundary that is extremely well sampled by the KBIS radar.  As this outflow boundary races ahead of convection, the actual tornado threat, which was never high to begin with, continues to drop even more.
ProbTor, on the other hand, places a tremendous amount of weight on LL AzShear,  resulting in a persistently high ProbTor values.

#MarfaFront

ProbTor Too High

Watching a supercell near Bismarck...
It was clear from the hail core aloft that this was severe. However, it was obvious around 2152Z that the RFD gusted out as was seen on reflectivity initially, and then later on the velocity images as the winds became less perpendicular to the beam. However, ProbTor continued to carry high probabilities, and even increased when it was clear on the velocity images there was no tornado threat.  ProbTor was only keying on the outflow boundary.  MRMS Rotation Tracks were also showing a swath of higher values along the outflow boundary.

Reflectivity Loop


SRM Loop

ProbSevere Time Series

-Tempest Sooner

ProbSevere ProbTor gets tricked

Upper left: Orange ProbSevere with a green ring signifying escalated ProbTor
Bottom right: Low Level Rotation tracks with green ProbTor Object associated with the green ring at upper left.
Lower Left: KBIS base velocity.



Key things to notice above - a spurious looking inbound maximum to the northwest of KBIS and a corresponding uptick in Low Level Rotation tracks in response to this shear zone that likely is just an artifact of sampling near the ground.  Below, we see ProbTor climbing to over 40% (red trace).  Be careful with ProbTor when the storm is close to a radar.

Suggestion: Instead of 0-2km, perhaps Low Level Rotation Track should be capped at the estimated LCL AGL.

#MarfaFront

ProbSevere

ProbSevere gives every indication of a severe storm over Morton County, ND (see ProbSevere read out below).  The Earth Networks lightning suggests there of 52 fl/min but GLM FED gives 0 fl, TOE 0 fJ, and AFA 0 km^2.  The two depictions below show those three GLM fields with the MRMS 1 km reflectivity.  Perhaps there is an issue with viewing angle at this northern latitude. - Jonathan Wynn Smith (ESSIC/UMD)

ProbHail: 93%; ProbWind: 95%; ProbTor: 5%
- MESH: 1.83 in.
- VIL Density: 3.20 g/m^3
- ENI Flash Rate: 52 fl/min
- ENI Flash Density (max in last 30 min): 0.89 fl/min/km^2
- Max LLAzShear: 0.007 /s
- 98% LLAzShear: 0.006 /s
- 98% MLAzShear: 0.008 /s
- Norm. vert. growth rate: 2101Z 1.3%/min (weak)
- EBShear: 38.0 kts; SRH 0-1km AGL: 155 m^2/s^2
- MUCAPE: 2925 J/kg; MLCAPE: 1657 J/kg; MLCIN: -36 J/kg
- MeanWind 1-3kmAGL: 26.4 kts
- Wetbulb 0C hgt: 9.0 kft AGL
- CAPE -10C to -30C: 546 J/kg; PWAT: 1.3 in.
GLM: max FED: 0 fl; sum FCD: 0 fl/5-min
GLM: max TOE: 0 fJ; avg AFA: 0 km^2
Avg. beam height (ARL): 1.28 kft / 0.39 km
Object ID: 273531
PS: 98

GLM - Apparent Poor FED Detection

GLM Flash Extent Density product seems to have poor detection from both GOES 16/17 in the high plains. Perhaps this is related to the greater viewing angle due to latitude and being farther on the periphery.  In this example, a very strong supercell was noted to have high total flash density values on ENTLN, while the GLM FED was very unimpressive. It was picking up on some flashes, but not enough to help the storm stand out from a lightning perspective. This could have negative impact on warning forecasters trying to use FED to identify stronger cells from a situational awareness perspective.



-- warmbias --