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| Figure 1: 21 June 2017 GOES-16 TPW (color) and IR (gray). |
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| Figure 2: 21 June 2017 LIX 12z radiosonde. |
- Bill Line, NWS
Wednesday, June 21, 2017
GOES-16 TPW Near Cindy
On 21 June, Tropical Storm Cindy approached the Louisiana Gulf Coast. The main threat with this system was heavy rain and flooding. The GOES-16 TPW baseline product provides forecasters with rapidly updating information about how much moisture is available in the atmosphere. Widespread TPW over 2.0" was sampled in the vicinity of Cindy, with some localized areas over 2.5" (Fig 1). These observations agree with nearby radiosonde data (LIX), which measured 2.36" of PW (Fig 2).
- Bill Line, NWS
- Bill Line, NWS
LIX: Tropical System (New Orleans)
Tornado Warning Issued prior to ProbTor identification: Warning environment is within outer rainbands of Tropical Storm Cindy.
- Warning decision mainly based on velocity couplet and mini-super cell appearance on reflectivity. Velocity couplet is weak and probably on the lower end threshold but ProbTor had not identified it by 19:35.
Velocity Couplet
- ProbTor identified the cell by 19:38z with a prob of 9%.
ProbTor at 9%
- 1946Z: 0.5 velocity signature weak, but ProbTor increased to 15% probability. Forecaster -Tahoe
EWP Week 1 Day 3 Operations
For day 3 of week 1 of the 2017 GOES-R/JPSS Spring Experiment, participants will begin operations in the Grand Forks, ND and New Orleans, LA CWA's. The New Orleans folks will monitor tornado potential associated with Tropical Storm Cindy.
Tuesday, June 20, 2017
EWP Week 1 Day 2 Summary
Our two groups of forecasters remained in the Dodge City and Chicago CWA's for the duration of Tuesday.
- Bill Line, NWS
- Bill Line, NWS
- GOES-16 ABI Imagery and products
- Imagery
- Sandwich product is a top 5 image to look at in operations
- Compared to RGB’s, sandwich was better. Looked at daytime convection, couldn't see much of the gradient in the cloud top temperatures. In sandwich, could see it well while preserving the gradient.
- Cheat sheets for various imagery bands and combinations will be very helpful
- Derived products (CAPE, LI, winds, dsi, tpw)
- Instability very low compared to SPC mesoanalysis and most model data
- In kansas, GOES cape was half as much as spc mesoanlysis and GFS
- Convection developed within the highest values of instability and TPW
- Channel differences
- RGB composites
- I am having trouble wrapping my head around the Airmass RGB
- GLM
- In Illinois, I used glm to try to get lead time to cg, but didn’t have lead time
- In kansas, GLM data provided lead time to first NLDN cg by around 20 min
- My favorite display was the 5-min product updating every minute.
- Most forecasters looked at the gridded events and flash combo.
- I like looking at the flash because it is what I’m familiar with
- For tv, would mostly show flashes, but maybe last frame would show the extent (gridded event) to get across that lightning can extend far from the storm core, and could potentially hit the surface far away from thunderstorm
- ProbSevere
- In illinois, the environment was marginal. Probsevere values stayed low confirming the low end threat. One report was from strong outflow with very low dbz, so probsevere had no probs on the outflow and very low probs with associated storm. This happens a lot out west, so would be nice to be able to track situations like this (outflow winds).
- Not much velocity data in the algorithm. Storm with high std, I saw this before probsevere increased. Would be nice to somehow incorporate more vel data.
- When I had a lot of storms and warnings going, probsevere was very useful. Instead of viewing all tilts with all storms, prob severe was great for SA, directing me to storms that needed attention. For all storms that were producing hail, probhail was over 95%. Gave me confidence that the same types of structures were being seen with new storms as with old storms.
- NUCAPS
- Afternoon pass confirmed low instability in our area. Storms did not go severe
- Using plan view display, looked at dew point depressions just above the surface, helped to confirm dry atmosphere.
- Loaded op and exp modified ahead of line. Experimental made well a mixed layer, added instability to around 500 j/kg. This even seemed a little high, considering convection was very weak.
- Modified was much better. Non modified had a lot of CIN, unbreakable, but we had explosive development., modified was much better. Went from 300 to 2400. Southern plains will get nice well mixed layer, but east coast you won't really get this.
- Some flag to show where NUCAPS is significantly different from a model would be helpful. Perhaps above a certain layer
- Cross section was useful to see how deep dry layer was
- Would be beneficial to have plan view CAPE of modified soundings
Some thoughts and observations on NUCAPS gridded data...
It's been interesting to observe and think about ways the gridded NUCAPS
data can be used in an operational setting dealing with convective
weather. The recent blog post highlighted lapse rates and their similarity to analyses provided by the Storm Prediction Center. For this one, I was going to take a quick look at Convective Inhibition (CIN) data as provided by the NUCAPS gridded data, in conjunction with satellite observations of the region. This first image shows the NUCAPS derived CIN data over the southern and central High Plains at ~19Z overlaying GOES-16 0.64 um imagery.
The color curve in the above image is set so that generally brither colors (light blues to greens) indicate higher values of CIN and thus regions where convection is being inhibited. Notice that low clouds can be seen in areas of western Kansas where CIN values are lower. The same can be said for portions of northern Texas. Meanwhile, CIN values are peaked generally in the TX/OK panhandles and parts of southern Kansas where there is little cloud development in this scene. Taking in the big picture here, this would indicate any development might be favored to continue in western Kansas where one cell can already be observed to develop. A post earlier showed that lapse rates were not that steep in this area during the early afternoon, however, steeper lapse rates just to the west were about to advect into western Kansas.
Forecasters are going to be inclined to check on the data individually and take it on an individual basis sometimes. Comparing the NUCAPS gridded data with the soundings can present some problems sometime. Take for example, the gridded data in the far NE corner of the TX panhandle. The observation at this point shows a value of ~279 J/Kg (of CIN) between the 850 and 500 mb levels, which is where the inversion is located in this area. Now, looking at the actual sounding for this same location shows different values.
Although not shown, the CIN values for a ML parcel in this scene according to the sounding data were about 600 J/Kg. Granted, this is just one example shown, but was representative of the broader issues. So, there perhaps needs to be a better way to obtain the gridded data so that there are no potential discrepancies between the NUCAPS Soundings data, and the gridded data.
-Kris W
The color curve in the above image is set so that generally brither colors (light blues to greens) indicate higher values of CIN and thus regions where convection is being inhibited. Notice that low clouds can be seen in areas of western Kansas where CIN values are lower. The same can be said for portions of northern Texas. Meanwhile, CIN values are peaked generally in the TX/OK panhandles and parts of southern Kansas where there is little cloud development in this scene. Taking in the big picture here, this would indicate any development might be favored to continue in western Kansas where one cell can already be observed to develop. A post earlier showed that lapse rates were not that steep in this area during the early afternoon, however, steeper lapse rates just to the west were about to advect into western Kansas.
Forecasters are going to be inclined to check on the data individually and take it on an individual basis sometimes. Comparing the NUCAPS gridded data with the soundings can present some problems sometime. Take for example, the gridded data in the far NE corner of the TX panhandle. The observation at this point shows a value of ~279 J/Kg (of CIN) between the 850 and 500 mb levels, which is where the inversion is located in this area. Now, looking at the actual sounding for this same location shows different values.
Although not shown, the CIN values for a ML parcel in this scene according to the sounding data were about 600 J/Kg. Granted, this is just one example shown, but was representative of the broader issues. So, there perhaps needs to be a better way to obtain the gridded data so that there are no potential discrepancies between the NUCAPS Soundings data, and the gridded data.
-Kris W
Gridded NUCAPS Verification
Gridded NUCAPS verified well with the SPC Mesoanalysis when comparing mid-level lapse rates:
Steep mid-level lapse rates (>7 C/km) are located near the Kansas/Colorado border on both analysis.
Westerly flow aloft was progged to advect the steeper lapse rates eastward into deeper moisture across western Kansas. This led to explosive development a couple hours later.
-Lost Met
Westerly flow aloft was progged to advect the steeper lapse rates eastward into deeper moisture across western Kansas. This led to explosive development a couple hours later.
-Lost Met
GLM Parallax error?
At first I thought that the GLM lightning was lining up with the gust front instead of the core behind it.
However, when looking at ENTLN lightning, it lines up with the core.
Davis Nolan
WKRN Meteorologist
Advantage of Modified NUCAPS
The modified NUCAPS soundings have shown significant improvement when compared to the operational NUCAPS soundings.
Here is an example where SBCAPE increased from 388 J/kg to 2770 J/kg in a modified NUCAPS sounding:
Even more significant is change in CINH from -533 J/kg to -27 J/kg--essentially going from a very strong (unbreakable) cap to a weakly capped environment.
Thunderstorms rapidly intensified as they moved into the environment sampled by the sounding.
Therefore, it seems reasonable that the modified sounding is a better representation of the thermodynamic environment than the operational sounding.
-Lost Met
Here is an example where SBCAPE increased from 388 J/kg to 2770 J/kg in a modified NUCAPS sounding:
Even more significant is change in CINH from -533 J/kg to -27 J/kg--essentially going from a very strong (unbreakable) cap to a weakly capped environment.
Thunderstorms rapidly intensified as they moved into the environment sampled by the sounding.
Therefore, it seems reasonable that the modified sounding is a better representation of the thermodynamic environment than the operational sounding.
-Lost Met
17 & 19Z SNPP NUCAPS Passes
Main Points:
1. Temporal Coverage
2. Experimental Sounding adjustments
3. Visualization of Data
4. Comparing Data sources
1. Temporal Coverage
Our CWA (LOT) benefited from two overlapping passes at 17z and 19z. Looked at soundings ahead of the convection to anticipate if any additional convection is expected across our southern CWA.
*I find this product becomes much for useful when we get multiple passes in the day. Ideally, get an hourly pass in the same location would be of much greater use when trying to monitor the evolution of the convective environment. In this case, the environment was not changing much, but is knowing this is still valuable information.
17z pass 19z pass
2. Experimental and Operation Sounding Comparisons:
Took a sounding point ahead of the convection in Kankakee County (LOT). Both showed the relatively dry and low CAPE environment that was expected but think the experimental profile may show a tad too much instability by assuming a perfectly mixed layer. Seems the moisture profile should meet up with the top of the temperature mixed layer which would result in lower CAPE as a result. No way to verify this though, just my thoughts.
Inspecting both the operational and experimental profiles helped confirm analysis seen from GOES-16 derived instability fields (CAPE, LI, etc).
That is:
I found visualizing data is much easier when displayed in a similar fashion to the GOES-16 plan view of derived stability indicies. Explored the available gridded NUCAPS fields (where available) and also provided increased confidence in the environment. Also showed the expected gradient in instability from north to south. The gridded display in NUCAPS could use work, the edges can be quite jagged and coarse looking. Also, had to compare MSAS dewpoints in F while the dewpoint depression in the gridded product was in Celsisus (image below).
4. Comparing Data sources
*One very valuable tool in NUCAPS its high vertical resolution. I was able to select a pressure level of interest to see, in this case, dewpoint depressions across the southern CWA. When compared to surfaces obs & MSAS analysis the gridded 925mb NUCAPS data, I found the same pattern of large dewpoint depressions to the south. This also reinforced my concern for continued outflow winds due to dry sub-cloud layer.
Forecaster: Tahoe
1. Temporal Coverage
2. Experimental Sounding adjustments
3. Visualization of Data
4. Comparing Data sources
1. Temporal Coverage
Our CWA (LOT) benefited from two overlapping passes at 17z and 19z. Looked at soundings ahead of the convection to anticipate if any additional convection is expected across our southern CWA.
*I find this product becomes much for useful when we get multiple passes in the day. Ideally, get an hourly pass in the same location would be of much greater use when trying to monitor the evolution of the convective environment. In this case, the environment was not changing much, but is knowing this is still valuable information.
2. Experimental and Operation Sounding Comparisons:
Operational
Experimental
Took a sounding point ahead of the convection in Kankakee County (LOT). Both showed the relatively dry and low CAPE environment that was expected but think the experimental profile may show a tad too much instability by assuming a perfectly mixed layer. Seems the moisture profile should meet up with the top of the temperature mixed layer which would result in lower CAPE as a result. No way to verify this though, just my thoughts.
Inspecting both the operational and experimental profiles helped confirm analysis seen from GOES-16 derived instability fields (CAPE, LI, etc).
That is:
- We continued to see a low instability and dry low-level environment across our southern CWA. This dry low-level was the main threat as we did observe many outflows running away from convection along with an observed wind gust of 67mph.
- This dry and low instability environment resulted in the expectation that no further deep convection was anticipated as the convective line traversed south.
I found visualizing data is much easier when displayed in a similar fashion to the GOES-16 plan view of derived stability indicies. Explored the available gridded NUCAPS fields (where available) and also provided increased confidence in the environment. Also showed the expected gradient in instability from north to south. The gridded display in NUCAPS could use work, the edges can be quite jagged and coarse looking. Also, had to compare MSAS dewpoints in F while the dewpoint depression in the gridded product was in Celsisus (image below).
4. Comparing Data sources
*One very valuable tool in NUCAPS its high vertical resolution. I was able to select a pressure level of interest to see, in this case, dewpoint depressions across the southern CWA. When compared to surfaces obs & MSAS analysis the gridded 925mb NUCAPS data, I found the same pattern of large dewpoint depressions to the south. This also reinforced my concern for continued outflow winds due to dry sub-cloud layer.
Forecaster: Tahoe
PROBSEVERE won't help with gust front
There was a measured gust of 67 mph and some tree damage in the area.
Justin Seiglaff explained that the gust front was detached from "the body" that was outlined, and therefore not included in ProbSevere.
That makes perfect sense, but forecasters looking at ProbSevere should be aware of that.
Davis Nolan
WKRN Meteorologist
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