NUCAPS Procedures Usefulness

The NUCAPS Quick  Guide from JPSS includes a few procedures. Here I show the utility of a few of those procedures for combining GOES Satellite data and NUCAPS data.
This procedure plots 400-200mb relative humidity and GOES-16 water vapor. You can see the representation of the dry air across the northern US and the systems in the Plains & southeast.



Another procedure compares GFS, HRRR, and NAM lapse rates with the NUCAPS lapse rate info. This is a good check to see if model lapse rates are performing well or where they need to be taken with a grain of salt.



Another procedure plots 850-300mb RH and low-level water vapor. The product shows the system in the Plains and the system in the Ohio Valley. Drying is also obvious in the southern Great Lake and North Dakota.



I like the procedures provided in the JPSS Quick Guide. I am starting to understand the applicability of the NUCAPS data little bit more. These procedures are helpful in contextualizing the provided data fields.

-Atlanta Braves

Decrease in GLM lightning activity coincident with 2 inch hail report

A storm just northeast of Amarillo developed quickly along a frontal boundary, and quickly showed supercellular characteristics with mid level rotation and a 65+ dbz core reaching about 35 kft MSL. 2 inch hail was reported with this storm during this time. GLM data again shows a decrease in both Flash Extent Density (top right) and Event Density (top left) show a notable decrease in GLM lightning activity while ground based radar remains fairly unchanged, and both the IR satellite presentation (bottom right overlaid on visible imagery) and radar data (not shown) indicate the storm maintained intensity and if anything, had strengthened a bit.



-64BoggsLites

Comparing NUCAPS Modified Soundings and 18Z RAOBs

A satellite pass at around 19Z allowed us to compare NUCAPS modified soundings with 18Z RAOBs. A comparison of a NUCAPS sounding near Amarillo seemed to reasonably represent the mid and upper levels with the 18Z KAMA RAOB. The NUCAPS sounding had slightly lower freezing level and -20C and -30C heights compared with the RAOB (10.9, 19.0, and 23.2 kft vs 12.2, 20.8, and 25.4 kft, respectively). The midlevel lapse rates were comparable at around 8.0 C/km. However, the NUCAPS sounding appeared to struggle with the lower levels, not representing the subsidence inversion evident on the RAOB, and being too cool and dry at the surface (T/Td of 20/17C on the NUCAPS compared with 24/19C on the RAOB). This led to lower CAPE estimates from the NUCAPS than were observed by the RAOB.





Similar results were seen in a comparison of the 18z KLMN RAOB with a NUCAPS Modified sounding near Lamont, OK:




Ron Dayne

AllSky as a good proxy for dryline location and CI

The AllSky Layer Precipitable  Water product showed utility in identifying and tracking the dryline as it moved into the Lubbock CWA. The dryline entered the CWA at about 1930 UTC.



Coincidentally, the KLBB radar shows convection initiation around 19:30 UTC as well.



And the convection continues to develop:



The AllSky product remains a very useful tool for situational awareness and 2-D environmental familiarization.

-Atlanta Braves

Comparing the modified and unmodified NUCAPS sounding from Western Oklahoma on May 23

While waiting for any convection to develop in PA, I ventured into western Oklahoma to do a comparison of unmodified and modified NUCAPS soundings in an area under an enhacned risk of severe weather. The soundings examined were near the Texas border (point E below).



We'll first look at the visible satellite and observations at 19Z.



Notice that point E is near a WSW/ENE oriented boundary. Obs near the point show temperatures in the mid 70s, with dew points in the mid 60s. So let's take a look at the unmodified NUCAPS sounding first.



It uses a surface temperature of 63F, and a surface dew point of 50F, both more than 10 degrees below the nearby observations. These inaccurately low values give, as one would expect, no sign of instability (CAPE=0). Looking at the modified NUCAPS gives a different picture, however.


In the modified sounding, the surface temp is 69, and the dew point is 65, which is much closer to the observed surface obs. This changes your surface-based CAPE to 2055 J/kg, vs. 0 from the unmodified. It also has a sharper low level inversion, which one wood expect based on the stratus deck in place.
To "verify", let's look at the SPC mesoanalysis.



Sure enough, the mesoanalysis shows CAPE at around 2000 J/kg.   Clearly, this is another case where the modified NUCAPS sounding is a noticeable improvement over the unmodified sounding.

Thorcaster

AllSkyLAP Resolves Dry Mid-Level Layer

An eastward moving plume of moisture and instability was clearly depicted in the GOES16-Merged GFS AllSkyLAP products.  Estimated MLCAPE in the lower left panel is similar to the SPC mesoanlaysis data.  Into central Pennsylvania, values were in the 500-700 J/kg range.  So certainly on the low end for severe weather potential in the State College CWA based on instability alone.  However, one interesting feature caught my eye in the 700-300mb AllSky PWAT analysis -- a west-to-east band of low values advecting through Indiana and Ohio into western PA. This mid-level drying is attendant to the eastern periphery of an EML that originated over the southwest U.S.  A plume of warmer 700mb temperatures in the RAP analysis matches up well with this dry band of mid-level air.  With the chance for scattered convection later today in central PA, the influx of a dry mid-level layer may aid in the production of strong convective winds/downbursts. -Roy

GLM Observations in the Tx Panhandle

A supercell moving northward along the dryline over the Texas Panhandle region underwent a split over the last 20 minutes or so. Preceding the split, there was a notable decrease in 5 minute GLM Flash Extend Density and Event Density.  After the split, there were to notable maxes in both of these products. However, in the GLM Minimum Flash Area, this trend was not observed due to the more coarse resolution of the product. Better resolution may have helped identify both updraft regions within the 2 storms after the split. Additionally, a downward trend was noted in 5 Event Density and Flash Extent Density despite no real change in the ENTLN lightning activity. A loop of GLM data and IR/Vis depicting  this storm split is below.



-64BoggsLites

Comparisons of NUCAPS and Model Data Lapse Rates...

So, it can be refreshing to see when NUCAPS data agree with model data, but I'm often more interested in those cases where there are differences, and potentially important differences.  Notice in the images below the comparisons between NUCAPS 850-500 mb lapse rates and various model data.

Image 1. 850-500 mb lapse rates from NUCAPS (upper left), HRRR (upper right), GFS (lower left), and NAM40 (lower right), valid ~18 UTC 23 May 2019

Notice the relatively large differences that stretch SW to NE from central W VA into New England.  Taking a look at nearby radar imagery, it's clear why this area had significantly lower lapse rate values in the NUCAPS data than the models; a line of showers and thunderstorms were present along this path of lower values that was displayed in the NUCAPS gridded data (Image 2).

Image 2.  850-500 mb lapse rates from NUCAPS (upper left), HRRR (upper right), GFS (lower left), and NAM40 (lower right), along with 0.5 Refl from the KCCX radar, valid ~18 UTC 23 May 2019

Of course, the NUCAPS retrievals certainly would have been affected by this area of denser clouds and precipitation.  Nevertheless, lapse rates would be affected (lowered) by the convection in those locations, which is depicted in the NUCAPS data only.  So, the lack of this feature in the models would then affect their forecast in this region going forward.  It will be interesting to see the NUCAPS forecast data in this type of scenario.  In fact, one of the forecasters here is taking a look.

-Kris W

Examining the NUCAPS FCST of CAPE

Below is a loop of the NUCAPS CAPE forecast for the afternoon across the CTP CWA.



Unfortunately, the product is very blocky, and makes it hard to use, especially since some of the missing data is in the time and place where high impact weather may occur. It's clear that it is trying to show some elevated CAPE moving across central Pennsylvania, but the values are very suspect to me given the missing chunks of information.

Thorcaster

Using Modified NUCAPS to help examine air mass downstream

The air mass in the CTP CWA has been modified somewhat based on earlier convection. Here's a NUCAPS sounding from central PA (note that it was yellow, meaning it IR retrieval failed due to clouds, but the microwave was successful).



Notice the low level CAP, as well as the modest mid level lapse rates of 6.1 C/km. To get an idea of the air mass characteristics, I looked at a couple of NUCAPS soundings further to the west. The first was west of Pittsburgh along the PA/OH border.



The mid level lapse rates were the same as further east, but the warmer temps and higher dew points were supporting non-zero SBCAPE values. There was still some CIN, however, and the MLCAPE was a paltry 23 J/kg.
Moving further west, I examined a NUCAPS soudning in central Ohio, potentially indicative of the air mass that would move into the CWA later in the day due to the mean westerly flow at mid and upper levels.



There was a noticeable difference in the mid level lapse rates, with a more significant value of 7.1 C/km.  Also notice the DCAPE was in excess of 1000 J/kg, compared to values of 500-600 J/kg further east. This would indicate that there will be at least a threat of severe winds with convection that develops later in the day in the CTP CWA despite the early in the day convection that modified the air mass during.

Thorcaster

TX Panhandle AllSky CAPE

A moderate risk for severe weather across portions of the Texas Panhandle today. Some convection is already on going along and north of a nearly stationary front stretched from the northern Panhandle into Kansas. Despite the cloud debris, the All Sky layer CAPE product still looks to be doing an acceptable job of analyzing the degree of instability present in the area. 18z values near Amarillo match well with the 18z special sounding at KAMA with values generally between 1600-2000 J/kg. The blotchiness of the all sky product between clear/cloud cover is a bit distracting, but the difference in values is a small enough magnitude that it does not compromise the forecaster's ability to use the product.



Dave Grohl

Examining environment using All Sky Lap PW

Covering the CTP (State College) area today. Initial convection has moved through, but models are suggesting redevelopment later in the afternoon along a front.  The help see changes in the atmospheric moisture, I've captured an animation of a 4 panel AllSkyLAP PW.



For reference, the upper left is the total column PW, the upper right is 1-0.9 sigma, the lower left is 0.9-0.7 sigma, and the lower right is 0.7-0.3 sigma.  What stands out to me surging eastward of lower values of the upper-most layer (0.7-0.3) towards the CWA, while the lowest layer (1-0.9) is remaining mainly unchanged. This suggests that the drying above the 0.7 sigma level (approximately 600-700 mb for CTP) may lead to increased values of DCAPE later this afternoon, so that any storms that do manage to initiate could have a threat of severe winds.

Thorcaster

Jefferson City tornado

A violent tornado hit the capital of Missouri last night at around 11:20pm local time. ProbTor showed rapid increases as well as some large fluctuations in probability prior to and during the tornado. After leaving Jefferson City, the storm continued to be warned and ProbTor again increased to probabilities ≥ 60% for about an hour; no reports of any kind were recorded during this time, however. You can see the archived time series of probabilities and predictors here.

Figure 1: Time series of ProbSevere products with NWS warnings and LSRs.

Figure 2: ProbSevere with MRMS MergedRef and NWS warnings in AWIPS2

GLM ENTLN comparison

Comparing GLM flash extent density and GLM event density to ground based ENTLN data along the Kansas/Missouri border region, there is a notable minimum in GLM data with a couple of the large clusters of ground based lightning clusters, while the other ground based lightning clusters seem to correlate relatively well with GLM data. Very strange indeed



-64BoggsLites

Lightning Jump in GLM FED, but not Earth Networks data

Storms continue just after 7pm near the Oklahoma/Texas border. A currently severe-warned storm saw a substantial and rapid increase in lightning activity observed by the GLM Flash Extent Density product. However, the ground based lightning network did not follow the same trend and remained fairly steady. The ground based data is more reasonable considering the storm did not experience any sort of significant strengthening during this time period. Earlier discussions with lightning detection experts suggested the low GLM FED count may be due to the location of lightning within the storm updraft region, which could impact how well GLM can sense it. That is difficult for the typical operational meteorologist to consider in real-time since it goes well beyond current training, and leads to decreased forecast confidence in the lightning data.



Dave Grohl

-82 C Overshooting Top Precedes FED Lightning Jump

GOES-16 10.3 um IR channel in the lower right panel captured an exceptionally cold overshooting top at -82 C.  This occurred toward the beginning of the animation at 2311Z in far northern Oklahoma (south of Coffeyville, KS) and preceded a large jump in the flash extend density (upper left).  The minimum flash area did not change much during this loop, so it may be advantageous for this component of GLM to have a higher spatial resolution than what is currently used. The GLM RGB product (upper right) merges the flash extent density, minimum flash area, and 10.3 um cloud top temperatures.  A group of bright cyan and white pixels helped highlight where all three of the aforementioned components were maximized.  In addition to a substantial increase in the flash extent density 5-10 min following the -82 C cloud top temp., ENTLN ground based lightning flash counts doubled during the same time. 

Although the environmental conditions already supported warning on this storm prior to the overshooting top (OT), seeing the FED and ground based lighting double, likely  in response to the intense OT, may push a forecaster to upgrade the severity of the warning (larger hail, higher winds etc.) -Roy

AllSky Layer CAPE Depicts Favorable Area for Additional CI

Additional convection was possible over southwest OK and/or northern Texas early this evening. AllSky product depicted a concentrated area of enhanced CAPE just south of the Red River, which is where the most robust CI took place right around 6pm.



Dave Grohl

GLM Predicting Strengthening Updrafts

A loop of GLM products, particularly the Flash Extent Density and the Minimum Flash (top left and bottom right, respectively), appear to have depicted strengthening updrafts in the Tulsa area. In particular, notice the uptick in Flash Extent Density going from Creek to Osage Counties, as well as the area over northwestern Rogers County. The increases in FED coincided with low areas of Minimum Flash Area.



The MRMS -20C Reflectivity product shows the strengthening updrafts over the same time frame:



The GLM products increased confidence in a decision to issue two SVRs.

Ron Dayne

Prob Severe Very Helpful Today

The Prob Severe Product has been very good for guidance today. See an example below.



Notice I have used an alternative color scale for the Prob Severe, but every cell with a Prob Severe of 80%+ (in black) was placed under some kind of warning. The prob severe was not the only tool used in the warning decision making process (as usual), but it was very effective in confirming the decision process using the base data.

Thorcaster

Verification of NUCAPS vs. Modified NUCAPS

NUCAPS data points from a polar orbiting NOAA-20 pass matched up with clear skies.  The following NUCAPS profiles were from the extreme southwest part of Missouri.



Unmodified NUCAPS profile from southwest Missouri, well south of Springfield.  Surface dewpoint was estimated at 57-58 F.  MUCAPE only up to 600 J/kg, with MLCAPE of 500 J/kg.



Modified NUCAPS data points from a NOAA-20 pass. Note data void through central Missouri....??? :(



Modified NUCAPS profile in same location as the unmodified sounding.  Surface dewpoint was estimated at 67-68 F.   High MUCAPE up to 3500 J/kg, with MLCAPE at 2900 J/kg.



Observed sounding from Springfield, MO at 18Z.  MUCAPE is 2500 J/kg, mixed layer down to 1000 J/kg.  The surface dewpoint was about the same as that of the modified NUCAPS. But the difference in MU/MLCAPE is significant.  I think the modified NUCAPS added value over the unmodified. Unfortunately, it seems a little overdone.  With that said, the instability probably increased between the observed sounding time of 18Z and the satellite pass near 1920Z.  An MUCAPE closer to 3000 J/kg is probably not too far off -- maybe by ~500 J/kg. -Roy

GLM flash rate, size, and RGB with IR

Loop on 22 May 2019, 21:36-22:06 UTC, showing a combined view of ABI Ch 1610.3 micron IR and GLM minimum flash area and flash extent density (top left). Other panels show the individual channels that contribute: FED (red), AFA (green) and IR (blue)

This pair of supercells near Tulsa, OK illustrates how flash rate and flash area information can complement one another. High flash rates and small flashes usually go together in a small updraft. However, at 2145 UTC the flash rate is much higher in the southern storm at the same time its minimum flash size is larger, with the opposite pattern in the northern storm. The northern storm was tornadic at this time. Shortly thereafter, the large flash rates decreased in the southern cell, and the average flash size became smaller, while cloud top brightness temperatures rapidly cooled and the extent of the anvil spread. The southern cell would soon go on to produce its own tornado.

The RGB panel in the top left combines the flash information together with the ABI 10.3 thermal infrared data: the coldest cloud tops and small flashes lead to a bright cyan color, and high flash rates push the colors further toward white. Early on the northern cell exhibits cyan colors while the southern cell is green and burgundy. Later, the southern cell becomes more cyan, while the northern cell takes on a more green hue.

Apparently, the jump in flash rate in the southern cell was an indicator of a strengthening updraft and the development of a mesocyclone. The drop in flash rate and minimum flash size might have been due to (1) a shift to small flashes that didn't make as much light, (2) extinction of light by an increasingly ice-rich, optically thick cloud, or (3) other instrument artifacts. While the explanation is less than clear-cut, synthesis of multiple sources of information improves the ability to understand the observations.

-deeplycloudy

ProbTor/ProbSevere Impressive Performance

There were 2 adjacent supercells heading into the Tulsa CWA and ProbSevere kept them as  separate objects (correctly) despite their proximity. This is a great sign. Additionally, the ProbTor product effectively differentiated between a tight couplet (north, 70% ProbTor) and a weaker couplet (south, 34% ProbTor).



This case shows the ability of ProbSevere to differentiate storms with distinct features despite close proximity. It also shows that ProbTor is doing what we think it should based on velocity features. -Atlanta Braves

NUCAPS availability maps

Working the SGF CWA this afternoon, I wasn't able to use the modified NUCAPS soundings, as there was a gap in the availability coverage right over that area. Below are maps of the modified sounding availability vs the reduced latency availability.




-64BoggsLites

ProbSevere handles intensifying storm well

The best storm so far went up in the far NE part of the OUN CWA and the ProbSevere model handled it well:



Note the lightning jump that occurs shortly after 21Z as well.



This is a nice supercell case! -Atlanta Braves

Comparison of NUCAPS modified and unmodified soundings at 19Z on 5/22

This post is going to compare the significant differences between the modified and unmodified NUCAPS sounding near Tulsa, OK at 19Z on May 22.



First a look at the unmodified sounding.  It actually shows a small temperature inversion near the surface in the boundary layer, with a surface temperature of 75, and a surface dew point of 61. This resulted in a computed surface-based CAPE of 362 J/kg, and a mixed layer CAPE of 148 J/kg. Now let's look at the NUCAPS sounding modified for the 19Z observed surface temp and dew point.



the modified NUCAPS soudning used the surface temp of 78 and surface dew point of 69. This caused a very large difference in the surface-based CAPE, with a value of 2277 J/kg (about 7X the unmodified).   The MLCAPE also more than doubled to 328 J/kg. Interestingly, the All Sky CAPE (which is designed to match the MLCAPE more closely then the SBCAPE) at the same time in the same area gave an estimate of  1627 J/kg (not shown). That would indicate that both the modified and unmodified versions significantly underestimated the instability, but the modified gave forecasters a much better idea of the potential based on the much higher SBCAPE.

I also noticed that the mixing process the modified NUCAPS used for the surface observation produces a rather unrealistic near surface profile. I think an improvement in the mixing scheme could improve the use of the modified NUCAPS soundings further. Despite that, the current modified does give a better indication of the convective potential in this case.

Thorcaster