Sampling Total PW gridded NUCAPS with contours overlaid on top, we see that the values are unrealistically high (over 3 inches). The 18 UTC soundings from the Twin Cities offices shows PWATs only around 1.30” which confirms this is incorrect. Also, the contours are in centimeters, not inches which is what the images. I plotted the NUCAPS sounding points to see if the points were “yellow” but it looks like the points were unavailable at this time step.

From this time step, the gridded NUCAPS matched up very well with the special 18 UTC soundings and the total PW values are realistic and make sense given the environment. Also the NUCAP points are all green which solidifies that the satellite was able to obtain a good sample.

– Fear the Shear

Comparison of a modified 18z NUCAPS sounding in far southern MN suggested a fairly accurate temperature profile (surface temperatures in southern MN were warmer than up at MSP.). NUCAPS did miss a pronounced dry layer around 700 mb, while it was too dry higher up especially around 500mb.

We also noticed some erroneous gridded NUCAPS precipitable water data round 16z across the Midwest (values of 3 to 4 inches). These looked more reasonable with the pass at 18z.

There was also 120 to 150% 850mb and 925mb RH.

The only satellite pass around that time was Metop-A. While the soundings were yellow, they generally were ok and didn’t match the gridded data.

– Barry Allen

Noticed some issues with the modified NUCAPS soundings in the FSD area.  In some of the cases where the odd errors in the soundings.  Not sure what caused them or why they showed up but here are some examples.

Note the odd look of the temperature trace in the mid levels (note the sharp increase in temp just above 700mb).  This was noticed in a number of the neighboring dots.  This error seemed to get better the further away you got from this location.  We were hoping this would improve when the second pass came overhead later at 20Z.  Below is an example of this error from the second pass.

As can be seen from the image above, the second pass still had this error (note the sudden change in the temperature trace at about 600mb).  After looking at the conditions in the area, several questions as to why this was occurring came up.  It appeared the surface temperatures were rather reasonable and the atmospheric conditions were also close to what the sounding may be trying to depict.  There was some thought the modified NUCAPS may be having difficulty with the moisture trace rather than the temperature trace.

It was also noted that when using the “pop up skew-T” function it would not see this error.  It was discovered the reason for this is the “pop up skew-T” function would not see the modified soundings that Nsharp would display.  

Why this was occurring I really could not tell.  One of the PIs indicated the algorithm may not be handling the moisture trace well.  It was also noticed the surface wind fetch was coming from the southwest and that is coming off the sandhills of Nebraska.  This is a very wet area and is perpetually wet.  Is it possible that some localized moisture advection was not accounted for?  Can’t say for sure but mention it here to indicate what could be going one.  

-Strato-Dragon

I was pleasantly surprised to see that when multiple sources of NUCAPS data were displayed at the same time that I could sample, via the pop up Skew-T and moving the mouse across the sounding swath, all sets of NUCAPS data and that it wasn’t dependent on which source of NUCAPS was ‘editable’.

However, depending on WHICH source of NUCAPS soundings was indicated as ‘Editable’ (in this case, the METOP-A – in blue), only those soundings could be opened in the NsharpEditor. Not necessarily a big deal but it is something that some folks may need to have explained to them.

Additionally, I have found the pop up Skew-T doesn’t always work. Often, it seems that when the NUCAPS data is more than an hour old or so, moving the mouse across the soundings results in no changes in the pop up readout. Is this related to the ‘age’ of the NUCAPS data or a bug with the pop up Skew-T?

Similarly, a new pass of data came in and I was unable to get updated readouts from the pop up Skew-T, therefore I ‘unloaded the “Radar Popup SkewT” (green legend, above), turned off sampling, then went back through the process of Volume > Popup Skew-T, turning on Sampling (right click), and sample cloud heights from NUCAPS (top of right click menu) and was able to then sample the NUCAPS.

– Guillermo