the California convection that could actually convect

A late season trof moving onto the west coast has everyone east of the Rockies excited for tomorrow and the weekend. It is associated with an unusually late season and significant rain event throughout CA with afternoon storms scattered about in the central valley, deserts, and Sierra Nevada. The GLM was able to detect lightning in several storms in CA and NV. NOAA-20 made an overpass around 21Z and provided several viable soundings in the San Joaquin Valley and near the CA coast.



The NUCAPS sounding centered in Tulare County is shown below. MUCAPE values on the order of 563 J/kg were supportive of low-topped thunderstorms.  Neighboring soundings indicated similar or slightly reduced values of instability. With the focus on severe convection east of the Rockies, it is nice to see NUCAPS perform so well in a completely different region and dynamical regime (namely post-frontal open cellular convection).




Brian Kahn

Earth Networks detects negative flashes in hail core

Over Indiana, there is a concentration of negative flashes where Minimum Flash Area is slightly larger.  This is colocated with a hail core shown in the Radar Hybrid Hydro Class.



-Jonathan Wynn Smith (ESSIC/UMD)

Were there indications there could be large hail in eastern IL?

Short answer: Yep.

NUCAPS Modified Sounding near Champaign/Urbana, IL from 18Z pass.

Since there were no 18-19Z special soundings from the IL/IN area, I looked to the AllSkyLAP CAPE which was only getting GFS retrievals in the ILX area. Those values were around 2300 J/KG or so.  The NUCAPS modified sounding near Champaign/Urbana, IL (shown above; the closest green dot to the storm that produced the severe hail), suggested more than 3500 J/KG of MLCAPE. Yesterday's NUCAPS soundings suggested that the NUCAPS CAPE values were a bit high, but the ProbSevere MLCAPE values at the time of the baseball size hail in Westville (2105Z) were near 2773 J/KG.  So, yes, plenty of sources suggested high CAPE and thus there could be large hail in the area.

Also of note: The operational GOES 16 CAPE did not show any values because of clouds across the area.

-Tempest Sooner

A Day to Compare

I initially wanted to compare model data, especially Skew-Ts, that I usually use, to the NUCAPS products. My purpose was to  ascertain the feasibility of replacing or supplementing  point based model products with NUCAPS. As I was unable to access the model data I use daily I decided to compare NUCAPS with NAM and GFS.

First the comparisons in the rapidly changing thunderstorm environment in which I interrogated a large MCS over the Illinois/Indiana border.
I compared NUCAPS 18z skew-t (from clear air area) to NAM and GFS skew-ts, at the same times and location.



NUCAPS presents a much more stable and dry environment than the model skew-t shows, and also much more stable than the actual current environment considering this storm has already produced hail, tornadoes and heavy rain.



Next, I compared an AllSkyLAP CAPE img at 18z (point J on the above picture),  to a NAM CAPE map over the same area/time. AllSkyLAP seems to be about 500J/kg higher than the NAM CAPE map.
Finally, I compared a NUCAPS CAPE img and the NUCAPS Skew-T at 18z over the same area and there was a huge variance. The skew-t was higher than the CAPE img by over 1300J/kg.



Lastly I decided to compare NUCAPS and model data from a stable area, non changing area.
I compared an observed skew-t from the KS/OK boarder to a NUCAPS skew-t. There is a one hour difference in the data but for the sake of this comparison I think this will work.



The observed skew-t is a relatively dry column with .87pw and a T/D of 31/20C  at the surface and 10/-20C at 700mb. The CAPE is at a ridiculous 3746 J/kg. But with no moisture, lifting mechanism nor shear I wouldn't expect development. When compared to the NUCAPS skew-t one can see a definitive difference. CAPE on the NUCAPS is at 0 with T/D at 24/11C at the surface and 7.9/-9.3C at 700MB which is a huge departure from what the observed skew-t showed...but how would the observed skew-t hold up to a model skew-t?



NAM 18Z model skew-t compared to the 17Z observed skew-t from the same area shows 28/17C SFC temps, only 3C off from the observed skew-t and at 700MB NAM shows 9.5/-8C only .5C off the temperature and 11 off the DP. Also, CAPE was much closer than when compared to the NUCAPS where SFC CAPE on the NAM is 3246J/kg and 3746J/kg on the observed.

Overall, after this small sample size of data, both severe weather and in clear weather, I believe that I would continue to use NAM/GFS over NUCAPS for my point based forecast needs.

VisIR Sandwich of MCS

VisIR sandwich product has been a very useful way to combine the high res visible imagery with the cloud top temperatures. However late in the day as the sun angle gets lower, the image gets darker. One way to remedy this is to adjust the composite options (right click on legend), and equally lowering the Gamma setting. This will brighten up the image and allow better utility into the low sun angle hours before sunset.

Default:


After:



How to adjust settings:



-- warmbias --

Eye Candy - Nothing More, Nothing Less

#CaptionThis

#MarfaFront

Prob Severe Object Identification

Prob Severe failed to identify a strong storm developing in radar sparse coverage area near Bozeman, MT. The storm did show up on MRMS composite reflectivity, ENTLN, GLM Lighting and had rapidly cooling cloud tops, so not sure what was missing to have the storm identified by Prob Severe.



--warmbias--

FED Gives Precursor to Strenthening Supercell, but...

Watching the last storm in the line that is still in Illinois, the Flash Extent Density values started climbing rapidly (between 1947Z and 2020Z), which suggested to me that I should start paying attention to it. Upon interrogation, the velocity started to change from being more convergent to rotational, and eventually it appeared that a tornado was likely per the KIND radar. Interestingly, that was when the FED fell rapidly (2022Z).

Clockwise from Top Left: 0.5 KIND Reflectivity, 0.5 KIND SRM, 0.5 KIND Vel, FED
There was also an increase in FED after the tornado signature became less intense, but when it wrapped up again, the FED decreased again (not shown).

Interestingly, I also looked at these same data with the new color curve that Jonathan and Kristin worked on today, and the increase and decreases in FED were not as clear, and I don't think it would have drawn my attention as quickly. Perhaps the lower values need to be more muted or less bright, but still within the same the rainbow color curve.

Clockwise from Top Left: 0.5 KIND Reflectivity, 0.5 KIND SRM, 0.5 KIND Vel, FED

-Tempest Sooner

5-min FED Colormaps

Testing a new colormap for FED using the Rainbow colormap in Python.  The first image depicts the modified 5-min FED with the modified colormap.  There is more variation on the lower end of the 5-min FED.  Will this colormap depict the variation in the more intense convection. The second image is the original 5-min FED colormap.  - Jonathan Wynn Smith (ESSIC/UMD)

Love the AllSky TPW!

Here's just a quick example of today's TPW over the Midwest where a complex MCS and discrete supercell are located. The blended TPW is very low-resolution and therefore you miss the enhanced values that might be located over IL compared to the rest of the upper Midwest and southeast U.S.  The AllSky products in IL are mostly using GFS, which may or may not be reliable, but at least it gives a better emphasis and resolution in where to focus your attention....as well as data underneath the severe storm complex. Over central IL, the TPW values are around 1.5 inch vs. the 0.9 inch for the blended TPW.
Animation below shows: Upper Left AllSky All Layer TPW, Upper Right AllSky sfc-900mb TPW, Lower Left Merged TPW, Lower Right Blended TPW



Below is a screen shot of the MRMS loaded at a similar time over the TPWs to see the impact of the cloud cover.

messing around with NUCAPS in the volume browser

A first cut at depicting the added value of the volume browser in AWIPS for NUCAPS soundings is shown below. I messed around with vertical cross-sections and time series of NUCAPS soundings in the upwind area of the MCS in northern IL that is expected to contain some potential for new convective initiation. Below is  the transect of the cross-section.



Here is the cross-section of equivalent potential temperature from NUCAPS at 18Z, NAM-12 at 18Z, and the HRRR at 18Z.



The two models and satellite soundings are in very good agreement at altitudes above 700 hPa, in less agreement between 700 and 850 hPa, and in poor agreement between 850 hPa and the surface. NAM12 is the highest with theta-e values between 336 and 344K, with HRRR about 5-10K colder, and NUCAPS still colder in the SW portion of the cross-section, and slightly warmer in the NE portion of the cross-section than HRRR.  Is it because of temperature or moisture differences?  It appears dominated by moisture discrepancies as shown below:



I can't quite figure out how to plot additional (or fewer) contours (AWIPS newbie here) but its quite clear that NAM12 is the moistest and NUCAPS is much drier near the surface. The 12Z Quad Cities RAOB had 7-8 g/kg for water vapor mixing ratio but with the six-hour discrepancy it is challenging to establish ground truth.

The volume browser is capable of making time series plots too.  Here is a ring of points depicting time series of 850 hPa temperature lapse rates over the last few days of soundings:


The time series plot is shown below.  A two-day time series of sparse satellite soundings  isn't all that insightful, but using this for 0-6 hour NUCAPS-FCST products (in comparison to model output) might be quite valuable for forecasters.



Brian Kahn

IDSS Usage from GLM/Minimum Flash Area

An MCS shifting southeastward across northern IL was producing quite a bit of lightning, and much of it was moving through the southwest portion of the line per Flash Extent Density. From a IDSS standpoint, the Minimum Flash Area and FED proved that it's necessary to look at both GLM products and ground based lightning products to see the "total" picture. The GLM products captured a larger flash that extended out into the stratiform area behind the main line that is not seen in the ENTLN and NLDN products. This information can be especially important for Airport Weather Warnings and/or outdoor venues. You can easily see that the flash extends almost back to the Rockford Airport, while the main line and most of the flashes are ~80 miles away. In other words, areas near Rockford Airport are not out of the woods yet for lightning.

Clockwise from top left: RALA, Minimum Flash Area, NLDN and ENTLN Lightning Plot, Flash Extent Density

-Tempest Sooner

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 --