Category: SPG2024

Reviewing Conditions Between the RAP and PHS

Posted in PHSnMWnABI, SPG2024 on by Kevin Thiel.

The PHS WRF will offer a unique means to compare RAP analysis and instability parameters. When observing what conditions were like in the PHS, it was noticed that the inclusion of satellite data resulted in drier conditions being observed at the lower levels across western Nebraska.

Satellite viewing of drier weather also corresponded with warmer temperatures across western Nebraska at the surface.

 

Now how does this look in comparison to various model fields in the RAP. On the bottom left are near surface dewpoints in the PHS, and on the bottom right is the RAP. Carrying forward into the simulation, the values for dewpoint were about 1-2 C below the RAP analyzed forecast. This corresponded better with surface observations within the area. Where the RAP had lower 60s lifting north, these have not been observed near surface stations at the same time. (Note color tables are different. Attempt to get this again was unsuccessful due to CAVE crash)
Here is the same post, but with the CAPE contours now shaded instead with the contours of dewpoint in Kelvin. The lack of a gradient in dewpoint conditions was more representative of the ground truth observed at different ASOS stations.

As far as the temperatures went and how it affected instability, you can also observe the RAP analyzing a cooler pocket, and it likely seems to be the result of the coarse model struggling to capture the terrain across western Nebraska.

What’s interesting is that the instability parameters are not completely different. The reason could perhaps lie in the observed data suggesting a warmer layer aloft. However, the RAP analysis did not differ significantly from the PHS data at 00z.

If you also look, the PHS also has a broader area of instability to the east compared to the RAP. This is where the PHS indicated higher moisture content, and it may be able to destabilize the region more efficiently as a result.

Finally, despite the drier air in comparison to the RAP, it indicated convective initiation about an hour earlier. Using the the forecast helicity and updrafts at 500hPa, one can see that initially pulse convection with minimal rotation should encounter an environment of increasing helicity. We shall see what comes out of this.

 

For forecast areas that may not have the benefit of features like WoF or other tools to analyze environmental conditions, looking at how differences in the satellite incorporated data and RAP mesoanalysis can help forecasters weigh environmental conditions and what they see from the RAP.

Kadic

Comparing OCTANE Day and Night Products with KSJT Convection

Posted in OCTANE Speed Sandwich, SPG2024 on by Kevin Thiel.

Wanted to make some observations comparing the day and night versions of OCTANE with convection in the KSJT forecast area. This is at about 1837Z.

 

For the most part, want to compare the speed product (left side) with the storm near Taylor County (bottom left part of the image). The day version is in the top left, and the night version is in the bottom left. There is detail in the day version that does not carry through to the night version. Of note: the anvil-top cirrus (slower motions) do not show up on the night version. Also, the magnitudes of the north and south lobes of higher speeds are muted somewhat on the night version.

Also want to note that the night version of the direction product (bottom right) shows a more significant shift in direction than the day version (top right). This is most evident with the larger shield of clouds over the top right part of the field of view, where more orange colors (about 200deg) are showing up on the northwest flank than in the day version (210deg-220deg). This is also evident somewhat on the storm in the bottom left part of the image.

It was also noted that overshooting tops in the night speed product appear as dark spots, which appears to be related simply to the IR  depiction of the storm. This is not a problem, as it draws the eye to the overshooting top / strong updraft.

–Insolation

Analyzing Clusters, Anvils Carrying Charge North, Final Checkup on LightningCast

Posted in DSS, LightningCast, SPG2024 on by Kevin Thiel.

Working on the DSS for the PGA tournament, one of the more frustrating features was how thunderstorms well outside the range of the event produced lightning. About the time one DSS image was sent, there was a lightning flash that occurred well north of the primary cluster and near a very weak area of reflectivity.

However, this has been the story for much of the day, where intense convection has been to the south and weaker cells to the north are still managing to produce lightning. Below is the probability of exceeding 10 flashes on GLM, with GLM and MRMS at -10 C to highlight how weak the convection was to the north. The fact that reflectivity was barely at 25-35 dBZ would suggest little potential for lightning.

 

Analyzing the RGB channels for lightning, one can see this evolution well. With more intense updrafts producing several flashes on GLM, they appear yellow. To the north, where it appears the anvil is carrying charge north, the flashes are very long. From a DSS perspective, this can be frustrating when communicating the potential for high impact weather when all that one gets are sprinkles and rumbles of thunder. Still, the RGB channel can be very helpful in delineating these features, but would also be a helpful means to suggest that the northern convection may not develop quite as much. The 50dBZ echo tops are intended to help highlight the stronger storms. Note how a few pixels of 50dBZ echo tops at best appear in the blue, while the larger cluster of taller storms have the younger convection. This also helped me consider parallax as well. Overall, I really like the potential for lightning characteristics divided into this RGB would be helpful in pulse convection.
And then later, the LightningCast began to behave a bit more oddly. Perhaps these situations cause it to become bouncy. Although, you can almost see these dips in the flashes on the chart as well. At this stage, I feel like I could tell the poor folks playing above par at the PGA tournament and taking forever that they can pack up their clubs and head home, because at this stage, the lightning is here to stay.
Outside of the one flash of lightning that took place over the event about when values crept upwards towards 50 percent, there was a flash. However, values had been hovering around 30-40 percent for much of the day. Values crept even higher, and yet there were no flashes nearby. It seems whatever convective debris left the region, and then the forecast became better overall.
Kadic

LightningCast Imagery Over Vis Satellite

Posted in LightningCast, SPG2024 on by Kevin Thiel.

One option that was experimented with for viewing LightningCast data was to use an image overlay on to of visible satellite imagery. Here is an example.

 

The underlying image is GOES-E meso sector visible imagery (channel 2). The overlaid image is LightningCast East probability of 10 flashes.

To get the image to look like this, the following changes were made to the LightningCast image.

1) In “Edit colors”, fill everything up to about 3% with zero. This ensures that there is no overlay to areas where LightningCast probabilities are very low, and the underlying visible imagery shows through cleanly.

2) In “Imaging”, change the Alpha value to about 25%-30%, and select “Interpolate Image”. I also liked increasing the brightness from 50% to around 60%-65%.

The end result is a display that draws your eyes to the convection with the greatest lightning probabilities, without being as busy as the contours. You could easily overlay extra information over this image, such as GLM, ground-based lightning, or environmental parameters.

–Insolation

Tracking Storm Strength With GLM and OCTANE

Posted in GLM, OCTANE Speed Sandwich, SPG2024 on by Kevin Thiel.
The GLM RGB, combining flash extent density and minimum flash area, highlighted the intensity trend of a cell in the northeast corner of the FWD CWA. The yellows of the RGB also corresponded with the uptick of cloud top cooling signatures shown from the OCTANE product. Using these products together I was able to track the intensity of thunderstorm, which took another uptick towards the eastern border of the CWA. The GLM RGB is definitely a useful tool in reading both the characteristics of the flash length and the flash density.
The OCTANE cloud top divergence product here is overlaid atop the visible satellite imagery with the cloud top cooling product, which may look a little messy to look at at first glance. After some practice with the product I was able to learn to pick out both the cooling and the divergence in a strong convective cell. In the third image I did remove the divergence product to have a good look at the cloud top cooling and visible satelitte signatures. After going back to the combination of the two however I found it easy to read what was happening among both the divergence and cloud top cooling with both displayed. I did like having cloud top cooling displayed on top of the divergence product as the divergence product was broader spacially and it made more sense to have the smaller scale cooling signals pop up above the divergence display.

 

 

-Joaq

Analyzing Differences Between OCTANE IR and Visible Speed and Direction Products

Posted in OCTANE Speed Sandwich, SPG2024 on by Kevin Thiel.

 

 

A number of features appear differently on IR and visible based OCTANE products this afternoon. First, the divergence of cloud top motion really stand out on the IR products, especially on the southwest storm in SJT’s CWA. The dark blues on the upshear side as well as the contrast of the red and green directional colors really appear well on the IR. In comparison, the visible based OCTANE speed product still shows shows the upshear values with the divergence signal, though it is a bit more subtle than IR. However the visible product allows us to see other features, like the above anvil cirrus plume on the southwest storm. In the cluster of storms to the northeast where this kind of feature isn’t visible, the visible OCTANE product still shows the strong cloud top divergence. OCTANE direction from IR shows divergence aloft a bit better than the visible product, though the difference isn’t huge. Finally, the color table adjustments done today to the Octane Speed IR product really help make the divergence stand out. Cloud top divergence in these products has been pretty well correlated with thunderstorm severity, so the IR based product seems like it would be very useful, especially at night.

-Joaq

SCP and SHIP from PHS is struggling in AWIPS

Posted in PHSnMWnABI, SPG2024 on by Kevin Thiel.

Not sure if something is going wrong with SHiP and SCP today, and it’s not a one off. Several cycles of  the PHS are behaving strangely. Although STP and MUCAPE appear to be ingested fine.

 

 

The values on the website also appear a bit strange with strange jumping behaviors with lack of gradients. An example of the SCP is shown first, and then SHiP second.

 

 

Here are the values on the RAP Mesoanalysis.

So not entirely sure what has gotten into the PHS model.

Kadic.

Two Storms… to Collide?

Posted in GREMLIN, OCTANE Speed Sandwich, SPG2024 on by Kevin Thiel.

The storm in Reagan County, depending on the data you look at, looked like they may merge! When looking at OCTANE/Visible satellite, the cell moving out of Reagan actually seemed like it was moving fairly rapidly eastward towards the stronger cell in Tom Green County. But, when viewing radar data, it wasn’t moving quite that quickly. Interestingly, GREMLIN has been hinting that these may merge (or is this a smoothing effect?).

OCTANE

 

KMAF (left) and GREMLIN (right)

 

Forecaster Cumulus

PHS Environmental Parameters vs RAP and Radar for Warning Ops

Posted in PHSnMWnABI, SPG2024 on by Kevin Thiel.

For this case, we have a data outage for radar, so the closest radar we have to use is KMAF for WFO SJT (no MRMS data either). Was looking at the tornado probability for the storm moving out of Runnels County since the midlevel meso was strengthening. So, I took a look at the environmental parameters from PHS (namely, the SRH). It looked like the storm was ingesting 800-900 m2/s2 SRH, which is a bit high, but the idea that the storm was ingesting more SRH/modifying the environment to possibly increase the tornado potential was useful. Interestingly, the RAP from the SPC Mesoanalysis page shows an area of enhanced 0-3 km SRH (just to the NW of the storm).

PHS environment parameters at 1947Z

 

SPC Mesoanalysis 0-3 km SRH
KMAF 0.9 deg tilt indicating a very strong midlevel meso

Another thought – Perhaps having either 30 minute data or intervals (30 minute, 1 hour, 2 hour, etc.) might help from a mesoanalysis standpoint.

Forecaster Cumulus