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