SPoRT is planning an assessment of Total Lightning products with several existing and new collaborators from WFOs, CWSUs, and National Centers, ranging in locations from southern Florida to New Mexico and Colorado. From May 15 – July 15, 2014 operational forecasters will evaluate the application of total lightning to support severe storm, public safety, and aviation weather warning responsibilities. To prepare, SPoRT is holding tele-training sessions with collaborators during the week of April 21 and has provided users several training modules as well as a Total Lightning Quick Guide. These can be found via SPoRT’s Training Page and on the NOAA LMS. Experience with total lightning data will prepare users for the GOES-R GLM as well as provide feedback from operations to researchers regarding the types of products users desire.
Archive for the ‘Training’ Category
During the weekend of Mar 02-03 2014, several weather features moved northeast across the area. The precipitation started out as rain across West Virginia with some freezing rain, sleet and snow across portions of southeast Ohio. Colder air began to filter into the region and as it did, the precipitation changed from rain to freezing rain to sleet and finally to snow. By 603 AM, the precipitation had turned to snow across all of West Virginia, but for portions of the extreme southeast counties.
I have attached two images from around 6 AM on Mar 3rd. The first image showed the radar data from KRLX at 603 am while the second image was the 607 am SFR product and 6 AM surface observations. When comparing these images, the “best” SFR signal for heavy snow was located along a line where the precipitation transitioned from freezing rain to snow. The heaviest signal in the SFR images was actually located over Mingo County where a total of 8 inches of snow was reported from the storm.
Freezing rain was falling across portions of extreme southeast West Virginia. Bluefield WV (KBLF) is located southeast of the “SFR” heaviest snow signal in an area where the SFR product is not showing anything. The SFR product did a great job across that area as the 6 AM KBLF observation indicated freezing rain was falling at that time.
SPoRT continues to work with select NWS WFOs in evaluating the NESDIS SFR product.
One thing to take into consideration when using data from “whisk-broom” instruments on polar-orbiting satellites, such as the Advanced Microwave Sounding Unit (AMSU) used to generate the SFR product, is that data at the edge of the swath (i.e. limb) may provide misleading or erroneous observations. As the instrument scans farther from nadir, it is looking through more of the atmosphere, creating both a bigger observation field of view (i.e., larger pixel) and having the signal attenuated by more atmospheric constituents (e.g., in-cloud and falling snow). As a result, when interpreting the SFR product, it is important to look for the extent of the swath (outlined in gray in the product in AWIPS) to determine whether the observed SFR is going to be limited by these limb effects.
Let’s take a look at an example over the NY Tri-State area for the post Super Bowl snow event. In the first image, from Metop-A valid at 1458 UTC, there is a large area of snowfall across the area. The heaviest SFRs appear to be around 1.2-1.5 in/hr (when multiplying the liquid equivalent by 10) across central and southern New Jersey. However, an hour later (see second image from Metop-B valid at 1554 UTC), the shape of the heaviest SFR has expanded north and west and there are now readings over 2.0 +in/hr. Other areas that had a SFR of less than 0.5 in/hr in the 1458 UTC image, appear to have a SFR of around 1.0 in/hr just an hour later, which is a large jump in intensity.
While it is certainly possible that the snow evolved and intensified in less than an hour, it is more likely that instrument limb effects are likely to blame for the larger SFRs in the second image. Make sure to check that swath edge when using polar-orbiting satellite data!
SPoRT continues to work with select NWS WFOs in evaluating the NESDIS SFR product.
A rare winter storm impacted much of the deep South Tuesday morning and afternoon. Areas of Central and Northeastern Alabama only received a couple of inches of snow, but this was enough to cause major headaches as roadways iced over resulting in highways across Alabama and Georgia being shut down, stranding thousands of motorists. Most reports from late Tuesday morning indicated that the worse of the winter weather was falling south of Cullman, AL, through Birmingham, AL to Montgomery, AL and then eastward into areas like Fort Payne, AL. I-65 north of Birmingham and I-20 east of Birmingham were particularly troublesome in the state of Alabama.
The AWIPS image below depicts the SFR product in AWIPS with overlaid interstate highways. This image was taken from the AMSU on Metop-B at 1618 UTC (10:18 local Alabama time) right about the time when the heaviest snow was impacting the state. The SFR Product indicates liquid water equivalent precipitation rates between 0.04 and 0.08 in/hr, which if you multiply by a factor of 10 to get the solid snowfall rate equates to around 0.4 and 0.8 in/hr. Snowfall totals across this region were generally in the 1-3 inch range, so the rates that were detected by the product were consistent with what actually fell.
On Jan 26 2014, an upper level shortwave caused an area of light snow across Ohio, western Pennsylvania and the northern counties of West Virginia. Surface temperatures were quite cold with readings generally in the teens. Even at these cold temperatures, the SFR product did indicate snowfall across the far northern counties of our forecast area.
The maximum snowfall rates indicated on the 1605 UTC product was about 0.3 to 0.4 inches per hour. Based on reports, these numbers appear to be representative of what actually was occurring.
While this is just one case, the SFR product appears to work reasonably well at temperatures below 22 DegF.
On Jan 25 2014, a mid-level shortwave moved across the region generating light to moderate snow. I have included screen captures of the 1118 UTC regional radar mosaic and surface observations…along with a 1120 UTC Snowfall Rate Product and surface observations.
It looks like the SFR product did not detect all of the snow that was falling around 11 UTC. But the misses can generally be described as either (1) the surface temperatures being too cold or (2) the probabilistic model, that is part of the calulations, indicating probabilities that were too low to determine if there was snow.
Once you know all of the details on how the product is calculated, I think this product did a good job at detailing where the snowfall was occurring.
The highest snowfall rates indicated by this image was around 0.3 to 0.5 inches which seems to be representative of what was occurring.
SPoRT is conducting an assessment of RGB imagery for Aviation and Cloud Analysis with Alaska WFO partners. A 17 minute training module for high-latitude application of nighttime RGBs with an Alaska example was created by SPoRT to support this assessment (see SPoRT training page to download or launch module). The Juneau WFO provided feedback for 1/24/14. Here is a part of their feedback regarding the value of the Nighttime Microphysics RGB imagery from MODIS and VIIRS and an example image from AWIPS/D2d.
WFO Juneau feedback:
“… the microphysics image was very helpful in picking out where the fog and low clouds were in the complex terrain that is the SE panhandle. most of the fog this morning was confined to the narrower valleys and channels while the wider channels were mostly clear. This is possibly due to higher winds still present in the wider channels limiting fog formation there. It also showed little or no fog and low clouds out in the gulf. The microphysics image was very helpful with figuring out fog for zone and marine forecasts. It also helped out with the TAFs with seeing if there were any higher clouds layers above the fog layer.”
When I examined the 1522 UTC SFR product, I noticed there was an absence of snow across our forecast area. Radar and surface observations indicated that light to moderate snow was continuing across most of our counties.
Per the Quick Guide, I checked the surface observations to see if the temperatures were about 22 DegF or colder. The temperatures across our northern and western counties were actually 22 DegF or colder. So the SFR product was behaving as it should across those counties.
However, the temperatures across the remainder of our region were above 22 DegF. The snow is definitely not lake effect as the current snow was still related to a shortwave which had pushed to our east.
What could be causing the lack of indicated snow across the portions of our area that still had surface temnperatures above 22 DegF?
I have attached a screen capture of the SFR product from 1024 UTC on 1/21/14. The label on the image is wrong. It states the units of the product are in/hr. But they are actually mm/hr.
During this time, we were having widespread light to moderate snow as an upper level disturbance moved across our forecast area. Reports around 2 inches of snow were common around the time of the product. We had received reports of snow coming down around an inch per hour. The maximum SFR detected in the product was 1.6 mm/hr…or 0.06 in/hr. Using a ratio of 15:1 yields a maximum snowfall rate around 0.9 inches per hour.
While we had several surface observations from which we could estimate precipitation rates, our WSR-88D was not operating correctly. The legacy precipitation were okay. But the Dual Pol precipitation products were not totally reliable due to equipment issues. So the additional information from the SFR product should have helped estimate the precipitation rates.
A well defined TROWAL feature that set up over the high plains from eastern NM into western TX and KS on December 21, 2013 was captured very well by the NESDIS snowfall rate product. A composite radar reflectivity loop in the first image below summarizes the overall evolution of this feature between 12 UTC on December 21st and 00 UTC on the 22nd (click image to loop and enlarge). Initially temperatures were too warm for snow across much of the area however as a potent cold front shifted south over the region rain changed over to snow. In the area of greatest instability the snow became heavy at times from near Tucumcari, NM (KTCC) to Dalhart, TX (KDHT).
The following series of images compare hourly precipitation reports at several sites across western TX and KS with the NESDIS snowfall rate product. The first image was captured at 2040UTC and the AWIPS cursor readout at KDUX (Dumas, TX) is shown. Note the observation is reporting an hourly precipitation accumulation of 0.05 (P0005) with moderate snowfall and a visibility of 1/2SM. The cursor readout comparison with the QPE product is 0.0544 in/hr. The following sample point valid for KPYX (Perryton, TX) is reporting a visibility of 1/4SM however no weather or precipitation is available since it is only an AWOS. However, the QPE product is sampling a precipitation rate of 0.1064 in/hr which converting with a simple 10:1 snow ratio would equate to heavy snow at 1″ per hour. The next image was captured at 2236UTC and the cursor readout at KDDC (Dodge City, KS) is shown. Note the observation is reporting an hourly precipitation accumulation of 0.07 (P0007) with moderate snowfall and a visibility of 1/2SM. The QPE comparison in the readout shows a rate of 0.092 in/hr. These values are exceptionally representative of the current conditions and the latency is less than 30 minutes.
After the storm system pulled out of the region the Snow-Cloud RGB product provided a stellar view of this mesoscale band of snowfall. Modifying temperatures over the following days significantly eroded snowpack in most areas except where the heaviest snow fell. Local storm reports obtained from the Iowa State website indicated between 6 and 11 inches of snow impacted the area within the central axis of the TROWAL feature.