The value of data fusion

We had an interesting storm develop in a radar gap in far eastern New Mexico yesterday. This is a great case study to demonstrate the value of data fusion in ProbSevere.

Figure 1 shows where the storm developed (the red circle), which was in a region of very poor "radar quality", as the eastern New Mexico KFDR radar was down. Thus, the closest radar was KAMA in Amarillo, TX.

Figure 1: Radar Quality Index for eastern New Mexico yesterday. The red circle is the approximate location of where the storm first developed. 

Figure 2: ProbSevere IntenseStormNet contours with GOES-16 ABI vis-IR sandwich product for a rapidly developing storm in eastern New Mexico.

One input into ProbSevere v3 is the probability of "intense" convection, as computed from IntenseStormNet. This is a deep-learning model that uses images of ABI 0.64-µm reflectance, 10.3-µm brightness temperature, and GLM flash-extent density to compute a probability of how "intense" the storm looks from a satellite perspective [paper]. 

The rapidly increasing IntenseStormNet probability, along with a favorable environment, and increasing total lightning flash rates helped jump the probability of severe despite poor radar reflectivity.

As the storm moved south and east into better radar coverage, radar reflectivity increased and the probabilities of severe further increased to above 70%. 

Figure 3: ProbSevere contours, MRMS MergedReflectivity, and NWS severe weather warnings.

Forecasters at the HWT have noted numerous times how ProbSevere v3 has increased before v2, particularly noticeable in the regime we've experienced this week, where the storms have had a dearth of lightning at the developing stages. At the time in Figure 4, this storm had PSv3 of 36% vs PSv2 of 12%. 

Figure 4: ProbSevere and MRMS MergedReflectivity for a developing storm in a radar gap in eastern New Mexico.

Later on, this storm produced numerous large hail, severe wind, and several tornado reports. Interestingly, the ProbTor v3 was much higher than ProbTor v2 prior to the first tornado report. In Figure 5, we can see PTv3 is 47% while PTv2 is only 9%. Looking into this deeper, we found that the environmental information such as the 0-1 km storm-relative helicity (~ 30 m^2/s^2) and the 1-3 km mean wind (~15 kt) were very low. The HRRR values in PTv3 were much better (~100 m^2/s^2 for SRH and 27 kt for the low-level mean wind). I believe this is an indication that PTv2 was too dependent on environmental information, compared to PTv2. This also demonstrates that the HRRR had a better handle on the environment than the RAP. You can see the low 0-1 km storm-relative helicity in the SPC mesoanalysis (Figure 6).

Figure 5: ProbSevere contours (the outer contour is colored by the probability of tornado), MRMS MergedReflectivity, and NWS severe weather warnings.

Figure 6: 0-1 km SRH (contours) and storm motion (vectors) prior to tornadogenesis. The red circle shows where the approximate location of the storm prior to producing tornadoes. 

Figure 7 demonstrates how ProbTor v3 was much higher than ProbTor v2 early on. The vertical black lines in the top-left two panels represent the times of the first and last tornado reports. The interactive version of these time series have been saved off and are available here.  

Figure 7: Time series of ProbSevere probabilities and radar, satellite, lightning, and HRRR attributes for the tornadic storm in Figure 6. 

Using Octane, GLM, and ProbSev for Warning Operations with Very Little Radar

 A severe thunderstorm warning decision in eastern New Mexico was a challenge today as it was within a KABX beam blockage and the eastern NM radar, KFDX, was down. The signs of the intensifying storm were found on satellite, GLM, and then slowly ProbSevere as the radar reflectivity heights from KAMA (the nearest valid radar) were very disorganized and slow to respond compared to the trends depicted by satellite and GLM trends. An above anvil cirrus plume, IR thermal couplet, consistent GLM FED/MFE signature, and cloud top divergence depicted by the Octane Speed/Direction product showed signs of strong convection developing. While reflectivity below showed just a minimal 50 dbz core and no 60 dbz core. As ProbSevere V3 gradually increased to around 35%, the ProbSevere ​Satellite Growth/Intense Convection Prob. quickly ​increased. The satellite growth/Intense Convection is not weighted as high in V2 and because of that ProbSevere was much lower at the same time.  While the radar reflectivity core was still missing, we decided to issue a warning for the storm given the other satellite based signatures. ProbSevere V3 began to show strong chances for severe weather approximately 13 minutes after the warning was issued, and a strong 60 dbz core developed on the KAMA radar shortly after with MESH getting as high as 3.5 inches.

GOES-16 Octane Direction.

GOES-16 Octane Speed.

GOES-16 GLM RGB

KABX 0.5 degree reflectivity.

KAMA 0.5 degree reflectivity.

KPUX 0.5 degree reflectivity.



 

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ProbSevere probability charts.

 

 

MRMS output showing radar data approximately 20 minutes after warning issuance.

 

-Thunderstruck

- Joaq

Using GLM to decide to issue an SPS

 GLM RGB showed the progression of a developing storm near the TBW DSS site this afternoon. Not only was lightning a threat communicated to the DSS site, but KTBW radar depicted a downburst signature as shown below, which prompted us to issue an SPS for wind to around 40 mph, frequent lightning, and heavy rain.  track a developing storm near the Florida State Fair

-Joaq

Using GLM to track thunderstorm life cycles

 GLM FED/MFA RGB here shows the rapid thunderstorm life cycles in the weakly sheared but highly unstable Florida atmosphere, as reds to yellows (intensifying convection with lots of short cloud flashes) give way to blues and purples (weakening convection with fewer but longer flashes). The range rings circle today's DSS event, which also highlights the difficult nature of producing storm by storm headlines or products for public safety as the life span of these thunderstorms are brief. The messaging for today highlights the consistently sporadic lightning threat for anyone on the coast or at the DSS site while storms build and collapse over a matter of minutes.

-Joaq

PHS and GLM Data for Tampa Florida this Afternoon and Evening

 General Risk for Thunderstorms in Florida this Afternoon and Evening

The Tampa CWA is in a general risk for thunderstorms this afternoon and evening per the SPC.

The main potential impacts are frequent lightning, heavy rainfall, and gusty winds thanks to decent amounts of SBCAPE.  Localized flooding  also remains possible, especially in urban areas,  due to slow storm motion as PHS shows no 0-6 km Bulk Shear over Florida. This matches well with the latest SPC Mesoanalysis which also shows no 0-6 km Bulk Shear shear over the region.

NUCAPS showing SBCAPE values at 21Z. Values are highest across the central and southern portions of the Tampa CWA. Areas in green had values around 1600-1700 J/kg. Areas in teal show values ranging from 800-1400 J/kg. Areas in purple range from 200-300 J/kg.  PHS shows a similar trend to NUCAPs with higher areas of SBCAPE across the central and southern CWA with lower values across the northern half of the CWA. However, the color scale on the online version of PHS is difficult to interpret as the gradient ramps up from light red to dark red. So, you cannot really pinpoint specific values of SBCAPE. However, you are able to see areas of lower SBCAPE and areas of higher SBCAPE at a glance. 

ProbSevere version 3 increases our confidence that storms will remain generally sub-severe as ProbSevere values are below 10% across the Tampa CWA as of 1930Z.The Octane Speed Sandwich product further confirms that storms are remaining below severe limits as the strongest storms are noted over southeastern Florida this afternoon as of 1930Z. Not only do these products help us pinpoint areas of potential severe weather, but they also help us pinpoint areas of sub-severe weather.  GLM shows lightning activity increasing across the Tampa CWA early this afternoon, and activity is expected to gradually increase in coverage as more thunderstorms develop through the late afternoon and early evening hours.  Lightning Cast around 1930Z shows lightning probabilities increasing across the Tampa CWA over the next hour. Pink contours represent a 75% chance of lightning in the next hour. Green represents a 50% chance, teal a 20% chance, and dark blue a10% chance of lightning in the next hour. GLM showing lightning activity increasing across Florida from 1930Z through 2016Z across the Tampa CWA. Areas showing more oranges and yellows have shorter flashes and more lightning density. These areas help us know where stronger updrafts are located. The strongest updrafts at the time of this loop remain outside of the Tampa CWA.  -Dwight Schrute

New Four Panel

 After a few days at the HWT I have decided to make a four panel of my own with the new products which has been working great! On the top left we have Octane Speed with Octane direction on the top left. We have Vis with lightningcast and GLM 1 min lightning on bottom left. On bottom right I have MRMS data and ProbSevere V3.  I was very happy with this display for situational awareness.

Also in the image below we can easily spot a stronger storm in a cluster of cells in Park County looking at directional and speed shear with Octane. Then we can quickly look down at ProbSevere and see its on the one storm being highlighted. That tells me this is the storm that I need to watch over the next 10-15 minutes for development.

-Thunderstruck

NUCAPS Low Level Lapse Rates Compared to RAP in Convection

 The 19Z NUCAPS sounding pass went over Florida as convection was ongoing across much of the state. The 850mb to 700mb lapse rate product picked up on some of the convective overturning in southern Florida where lapse rates were far less steep than other portions of the state (indicative of cooler low levels), as well as where low level lapse rates were a bit lower over the western coast. This lines up well with where the RAP was showing lower surface to 3 km lapse rates. Though these two levels are not completely analogous , they represent similar processes post-convection. However, the NUCAPS pass is also picking up on lower 850-700mb lapse rates over Georgia and South Carolina which doesn't match with the lower lapse rate product from the RAP, but these areas were also not experiencing convection so the reason for this could be due to other factors.

-Joaq

Outflow Boundary Heading Towards Florida State Fair DSS Event

 Outflow Captured by Radar and Octane Speed Sandwich in West Florida 

An outflow boundary tracking west towards a DSS Event in Tampa shown via radar. The outflow could be seen up to 20000 to 2500 feet MSL on radar.  Octane Speed Sandwich also captured the outflow boundary approaching the DSS Event.

-Dwight Schrute

Splitting Supercell Over SW TX

This is an 80 minute loop (in 1-minute increments).  The visible imagery with an experimental GLM RGB overlayed shows a splitting supercell over SW TX on the afternoon of 5/25/23.-Champion

Evolution of LightningCast Over Southern Montana/DSS Event In Billings

 Upper level flow shows continued SSW flow aloft over the region, thanks to deep troughing remaining over the West Coast. Overall forcing through the afternoon is on the weaker side of things, but models show an upper level jet streak nosing into the area. Scattered thunderstorm activity has already developed (below) to the south of Billings in northern WY, and is expected to expand in coverage through the afternoon. The DSS event is noted by the large yellow "B" over Billings.

The 14Z PHS forecast output (below) showed 19Z MUCAPE values across the area ranging roughly from 1000-2500 j/kg (with highest values in the eastern areas). Looking further into the mid-afternoon hours, outside of MUCAPE values creeping closer to 3000 j/kg in far NE portions of the CWA, the PHS overall didn’t show any notable changes in values. PHS values of 0-6km shear also matched up fairly well with SPC Mesoanalysis at 19Z, and had values increasing to around 35-40 kts through the afternoon.

Below is the 19Z MUCAPE via the SPC Mesoanalysis page.

LightningCast right around 19Z showed the 10% probability contour still about 40 miles SSW of Billings at its closest point (below).

LightningCast right around 20Z showed the 10% probability contour still about 30-35 miles W-SW of Billings at its closest point (below).

Around 2045Z, the 10% prob. contour reached the DSS event(below), but overall activity continues to be slow to push NNE. The LightningCast Time Series is included to show the trend up to this point.

Fast forward to roughly an hour later (~2140Z), there’s been a bit of a jump in the LightningCast Probability/TimeSeries (below), with the DSS event now sitting with a roughly 35% probability of lightning in the next hour.

A few minutes later, another jump up in probability - up to around 50%. Below is an image that has the GLM FED (colored pixels) included with the radar, LightningCast, and ENI Total Lighting Plot.

You likely have already been talking with the DSS contact point, but this jump up in the last ~10 mins may warrant another update, conveying that there is an increasing probability of lightning occurring in the next 60 mins.

Not surprisingly, the LightningCast probabilities have continued to increase, also shown in the time series. Image is from 2220Z.

What’s the best way to pass along this information to the DSS contact point?

With this type of event, where it’s slow to move in (driven more by the upper forcing vs the somewhat random quicker-developing activity that can occur in high CAPE/low shear  and other types of environments) and no significant changes in the overall environment across the area, perhaps you could wait until it’s closer to 50% or more  before expressing greater concern for the threat of lightning.  In those instances where activity may be quicker to develop/strengthen, it's not out of the question that values closer to the 25% contour would warrant greater concern. No matter the overall environment, I do believe the addition of a shorter-term probability (lightning within 30 mins)  would be beneficial.

- Bubbles

 

LightningCast And A Splitting Supercell

 This is a 2-hour loop (in 1-minute increments) over SW TX on the afternoon of 5/25/23.  The visible imagery is overlayed with GLM, LightningCast, and CG Flashes for NLDN and ENTLN.  Notice how the LightningCast is able to track the splitting supercell.

-Champion

Extreme GOES-18 Parallax Over Florida

 This animation shows the effects of parallax with the GOES-18 satellite imagery over the west coast of Florida. Overlaid on the GOES-18 visible product is MRMS Maximum Estimated Size of Hail (MESH). You can see MESH objects within the updrafts near the coast line while the associated anvils are well to the east (the displacement a product of the parallax). While GOES-18 wouldn't likely be used operationally at an eastern location, it does show a potential operational use of MRMS and satellite display together, showing the characteristics of the thunderstorm visually with the estimated hail size derived by radar (among other MRMS calculations).

-Joaq

Octane Direction Corrected Wind Speed Color

Octane Direction is a useful tool but changing the color table helps. I think we need get away from the pinks and reds. The top image is the corrected color table while the bottom was the uncorrected. Some of the stronger storms still stick out with divergent but a lot of the weaker but still significant outflows are masked by the pinks and reds. For me to get these results I did need to change the table to only go to direction 270 which made everything from 270-360 the same color, which in the current environment worked well. I am hoping with some more experimenting we could find a color table that goes to 360 that looks more similar to the upper picture.  -Thunderstruck

Growing Lightning Threat in Carter County, MT

 

Growing Lightning Threat in Carter County, MT

LightningCast probabilities steadily increase across Carter County, MT (Far SE MT) through the late afternoon. Perhaps the user could opt to select a more detailed range of probs by using the density radio button option in the product menu. At the moment only the 10/25/50/75% probs are available.

Probailities for lightning are steadily increasing over Carter County as convection forms along the cumulus field observed running SSW to NNE across the county. 

Surface-based CAPE from the PHS product indicate values increasing to 2,000+ J/KG across far SE MT.

- Rain-Free Bass Guitar

PHS 0-3km SRH for WY/MT - 5/25/23

 

PHS 0-3km SRH for WY/MT - 5/25/23

Shear parameters are highlighted for the afternoon time period across Northern WY and far Southern MT (northwestern portions of the image domain). Radar observations later on indicated this product did well, with several cyclic supercells moving NE to ENE across far Northern WY, and entering into Southern MT at the writing of this post. This product demonstrated higher resolution, though similar placement of convective elements from the same product on the HRRR model.

 

PHS 0-3km SRH - 20Z - 5/25/23

PHS 0-3km SRH - 21Z - 5/25/23

PHS 0-3km SRH - 22Z - 5/25/23

PHS 0-3km SRH - 23Z - 5/25/23

- Rain-Free Bass Guitar