Chilly Weather Provides an Opportunity to Utilize HMT-Southeast Pilot Study Observational Tools

The HMT-Southeast Pilot Study (HMT-SEPS) is a field project intended to be the first step in examining various scientific questions across the Southeast with a goal to define a long term HMT-SE research agenda. The HMT-SEPS project will largely focus on quantitative precipitation estimation (QPE) in western portions of North Carolina with some observational resources placed or supported in central and eastern North Carolina. As we head into the cool season, we wanted to note the utility that some of the observational tools, which include profilers and vertically pointing radars, will have during winter precipitation events.  Real-time access to the products from the various observational platforms is available on the web at: http://www.esrl.noaa.gov/psd/data/obs/datadisplay/index.php?ProjectID=7

During the overnight hours of 23 October 2013, a large shield of rain associated with an area of low pressure was shifting east across the eastern Carolinas.  The rain ended at around 08 UTC in New Bern NC, where several HMT-SEPS observational platforms are located. The precipitation was just rain at the surface with temperature in the upper 50s. The image below is the “Snow Level Plot” product from the New Bern, NC (ewc) 3GHz Precipitation Profiling radar from around 20 UTC on 22 October to 20 UTC on 24 October.  This product shows the vertical radial velocity in meters per second with the most recent observation shown to the left in the image. A change in velocity is noted by the transition from the cooler yellow and blue colors to the warmer red and orange colors. This transition is indicative of a change in the fall velocity from slower speeds associated with snow to a faster rate associated with rain which has a faster fall velocity than snow. The black dots indicate the snow level identified via the radar-based algorithm (the snow level can be interpreted as similar to the melting level). Note that the average snow level determined by the algorithm at 23 UTC was 11,476 feet which was very close to the freezing level (RADAT) reported from the KMHX radiosonde which was released shortly after 23 UTC about 24 miles (40km) to the southeast and indicated a freezing level of 11,800 feet.

new.bern.snow.level

On the evening of 24 October, a weak disturbance moved across the southern Appalachains and produced an area of light rain and snow showers across western NC  between 00 and 03 UTC on 25 October. Surface temperatures generally ranged in the lower to mid 40s in the Piedmont but dropped into the lower and mid 30s across the higher elevations of the mountains.  The “Wind Snow Level Plot” product from the Marion, NC (mro) 915 MHz Wind Profiler and Radio Acoustic Sounding System is shown below.

mario.snow.level

At this time the “Wind Snow Level Plot” showed the light rain and snow showers that moved across western NC. The profiler also showed a drop in the algorithm identified “snow level” or “melting level” with the heights falling into the 3000-4000 foot range where some minor snow accumulations were observed including up to a half inch at Beech Mountain.

pns.20131025

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