Researchers at the National Environmental Satellite and Information Service (NESDIS) have recently wrapped up development of the latest iteration of their Snowfall Rate (SFR) product to aid WFOs in situational awareness of snowfall events and snowfall forecasting. The developers within NESDIS have teamed up with SPoRT, utilizing SPoRT’s unique transition, training, and evaluation capabilities to deliver the SFR products to several WFOs in the CONUS and Alaska. During the evaluation period this winter, I will be evaluating the SFR and merged SFR products for use mainly here in the Tennessee Valley (provided the atmosphere obliges), but I will also be looking at the product CONUS-wide (and perhaps AK too, as the opportunity affords).
The SFR products are being delivered in two main versions: a merged snowfall rate product (merged polar-orbiter and radar data) and a product that contains only data from polar orbiters. Through collaboration with researchers and forecasters (especially at the Boulder NWS office), SPoRT is including SFR data with liquid to snow ratios of 10:1, 18:1, and 35:1. These data are being ported in AWIPS II workstations at the NWS offices. In the merged product, the polar swath data are complimented with NSSL’s Multi-Radar/Multi-Sensor (MRMS) precipitation data, and update much more frequently (every 10 minutes). Swaths containing polar orbiter data of course come in as associated polar orbiter swaths cross a region, with updates from about every 30 minutes to as long as ~4-5 hours over any location.
A look at the products the past several days has brought the opportunity for some initial evaluation. So far, the SFR product looks rather promising. Here’s a quick look at the product as a snowstorm was ongoing yesterday evening (Dec 15th) across the northern/central Rockies and the Northern Plains. The loop below (Image 1) shows data from 0110Z through 0410Z 16 Dec 2015.
Image 1. NESDIS Merged Snowfall Rate Product (showing 10:1 liquid to snow ratio) 0110Z to 0410Z 16 Dec 2015
The loop above shows the Merged Snowfall Rate product (displaying 10:1 liquid to snow ratio). Most of what you see is the MRMS precipitation during the loop. At the end of the loop however, you will notice a sudden expansion of the apparent snowfall over the region as an insertion of snowfall rate derived from a polar orbiter swath is incorporated into the product. So, let’s take a closer look at that single image containing the polar orbiter data (Image 2).
Image 2. NESDIS Merged Snowfall Rate product (10:1 ratio) with polar orbiter data insertion, 0410Z 16 Dec 2015
In the image above, you will notice that MRMS data remain and replace satellite retrievals where these data are available. That is, the MRMS data take precedence over the satellite data in the merged SFR product. However, data are inserted for locations where snowfall is detected by satellite instruments and radar (MRMS) data are not available. For large areas of Wyoming and Colorado, where radar coverage is certainly more limited, notice that the insertion of polar-orbiter data allowed for a more thorough and proper analysis of locations likely experiencing snowfall. Many of the surface observations (in yellow) likewise corroborate the snow that was occurring, particularly for locations in Wyoming, where coverage from radar data alone was very lacking. However, there are some surface observations that do not corroborate where the SFR product is indicating snowfall. Multiple reasons for this apparent discrepancy may exist, but it’s important to remember that the polar orbiting satellite instruments are detecting snowfall in the clouds. Some of this snowfall may not be reaching the surface due to sublimation aloft. Also, the snowfall could be very light and patchy in some instances with detection issues at some of the automated ground observation sites.
Now, let’s take a quick look at the polar orbiting data alone (Image 3).
Image 3. NESDIS SFR product (liquid to snow ratio 10:1) 0345 UTC 16 Dec 2015
The resolution of the polar orbiting data still allowed for the detection of banded structures across parts of the Dakotas that were evident in the MRMS data.
Further evaluations and posts about this product will be forthcoming as we progress through the winter. Perhaps I’ll have the chance at some point to evaluate the product here in the Tennessee Valley…that is, if the current mild Eastern U.S. pattern changes.