SNPP NUCAPS vs Experimental NUCAPS over Eastern Seaboard

NUCAPS soundings for New Jersey, Delaware, eastern Maryland, and the rest of New England became available around 19:30z for the 17z observation (technically approximately 1730z). The vast majority of our CWA (Philly/Mt. Holly) remains socked in with strato-cumulus. I chose to look up stream across southern Delaware and far eastern Maryland for sites that offered minor data quality issues. I chose a point near KSBY or Salisbury, MD and looked at several other points.

Here is the 17z sounding from NUCAPS.

The surface conditions on this sounding were off from surface conditions observed at KSBY at 17z. KSBY had an observation of 94/76, while the NUCAPS sounding started at 83/69.

I made these adjustments as well as some modifications to the boundary layer points to make it more realistic, this improved it's instability calculations.

Here is the 17z initialized RAP sounding for the same latitude and longitude as the NUCAPS sounding above. Comparing the two, the mixed layer and surface based CAPE calculations are now more similar.

 
The SNPP NUCAPS has trouble resolving the boundary layer, this is a known issue. Therefore, my first move was to modify it using the surface observation as a starting point. With that said, after working with the SNPP NUCAPS, my co-worker, GOB, loaded up the Experimental NUCAPS sounding which became available around 20z.

 The Experimental NUCAPS did much better resolving the surface conditions, with a surface observation of about 95/75. It's Instability values are bit more, especially the 3800 J/Kg of mixed layer CAPE. This is likely due to the sharp dew point increase off the surface through 900 mb. With modification, Instability values were closer to the RAP/HRRR/3km NAM soundings.

In short, the experimental NUCAPS soundings were more representative of the environment than the SNPP NUCAPS, primarily due to their better representation of the surface/boundary layer.

However, the timeliness of the soundings remains an issue, 1.5 to 2 hours after the observation. If this can be resolved, these could be better used by forecasters. With that said, it still took upwards of 15 to 30 minutes to interrogate the validity of the soundings, comparing surface observations and mesoscale guidance. I still worry this could be sticking point for forecasters, the level of work put in to quality control may not be worth the effort, especially in a faced changing convective environment.

If I had to chose between the two suites of guidance, I would lean toward the Experimental NUCAPS.

Dale Doback