The 2017 Summer Experiment at the Aviation Weather Testbed has begun, it’s focus centered on mock ups of the operational Traffic Flow Management (TFM) Convective Forecast desk (TCF), and on the Digital Aviation Services ceiling and visibility effort. Yesterday was a spin up day, allowing forecasters to peruse various new datasets as they explored the mock desks.

While the tropics were not in the overall experiment plan, it was difficult not to turn the attention southward to Franklin, particularly when new Geostationary Lightning Mapper (GLM) data was available.  The GLM data is optical, meaning that the concept of detecting lightning is much different from typical terrestrial networks. Therefore, developers at the AWC have been exploring various methods of displaying this data as a grid. Below is an example of the GLM groups, a ten minute average estimated every two minutes.

GLM group lightning density associated with Franklin on August 7th – a ten minute average ever two minutes. THIS DATA IS PRELIMINARY AND NON-OPERATIONAL!

Participants also were able to look at groups as an energy density, also averaged over ten minutes every two.

GLM group energy associated with Franklin on August 7th – ten minute average every two minutes. THIS DATA IS PRELIMINARY AND NON-OPERATIONAL!

These grids were designed for the AWC’s N-AWIPS systems, both created on an eighth of a degree grid over the entirety of the GOES-16 domain. When zoomed in, the grid points are noted to be pretty coarse. However, these particular displays were designed with AWC tropical and global forecasters in mind, folks whose perspective is broader. In their eyes, this coarse resolution isn’t a big issue. For others, such as TCF and Convective SIGMET, it may be that a similar display with higher resolution will need to be created. Additionally, gridded plots of the group energy density are also being added to the selection for later in the experiment.

Why gridded plots? As mentioned, GLM is an optical sensor, collecting lightning data in a very different manner than ground based networks… i.e. point data from that optical sensor does not equate to point data taken from a ground-based sensor calibrated to pick up a specific frequency. Therefore, it is important for forecasters to examine data with a different perspective than they have with other lightning data in the past in order to glean it’s value. For that reason, AWC has started the exploration with grids.

Over the next two weeks, we plan to take a cautious approach, keeping the known data quality issues in mind while collecting feedback and exposing forecasters to this new exciting data.

Squinting into blowing dust rivals trying to see through a lake-effect snow squall. However, unlike snow, this particular phenomenon is nearly invisible to radar and satellite alike. So the question is, how do we see and forecast for something so obvious to the naked eye and yet so invisible to our traditional instrumentation? This is a question that AWC forecasters at the FA desks face on various occasion and is what makes blowing dust SIGMETs so difficult to issue. One such occasion occurred this past Wednesday, April 8^th. A strong upper level system was positioned over the Southwest U.S. and the associated upper level jet had surface winds in the afternoon gusting to 30+ mph, particularly across New Mexico (Figure 1).

Figure 1. 20140408 1800 UTC GOES-W visible imagery and surface obs. Winds were 20-30 mph, with 30 mph+ gusts.

The forecaster working the FA desk was expecting these winds to result in blowing dust and at the beginning of shift requested to use the VIIRS/MODIS dust enhancement (provided by CIRA) to try and better identify any areas of dust that would arise. With approval for a temporary transition of the product to operations, the tool was able to be utilized in this case. By 1800 UTC winds had begun to pick up and radar reflectivity from Albuquerque showed some weak echoes indicating perhaps some dust being lofted. However, surface observations for the next couple of hours remained clear.

At 1940 UTC the first useable MODIS pass arrived, shown below in Figure 2. While it showed some weaker indications of dust in the Four Corners area, the majority of New Mexico remained clear.

Figure 2. 20150408 1940 UTC MODIS dust enhancement over the Southwest. Note the pale yellows in the Four Corners area

Additionally, the forecaster took a look at GOES sounder dust enhancement imagery available on the web. Though a coarser resolution, the weak indications of dust in the Four Corners were noticeable in this imagery as well (Figure 3).

Figure 3. 20150408 1802 UTC GOES sounder dust imagery. Note the yellows in the Four Corners area.

Though there may have been some lofted dust, the few weak radar echoes and overall clear surface observations indicated that it was not widespread or thick enough to warrant the need for a SIGMET. The FA forecaster was collaborating with ZAB (Albuquerque CWSU) during the afternoon hours and passed on the link (http://rammb.cira.colostate.edu/ramsdis/online/goes-r_proving_ground.asp) to both versions of the dust enhancement imagery. As the satellite-derived imagery seemed to be supporting their original assessment and lacked any strong dust signals, a final decision was made not to issue the SIGMET.

Although this ended up as a null case, it still shows the value of the satellite-derived imagery as a decision support tool at the AWC. As previously mentioned, dust is very difficult to pick up on any traditional imagery. However, the VIIRS/MODIS dust enhancement is able to bring this invisible hazard into view and provides additional and valuable situational awareness for blowing dust SIGMETs.

Yesterday I asked one of my forecasters if they were especially busy out on the floor given Sandy’s progress through the Northeast. He began to say yes, but then paused, laughed, and said instead, “Not really. I mean, there’s nobody flying out there right now.” His statement was quite true, as yesterday at 4 pm, the number of cancelled flights had grown to more than 19,500, with more expected as the NY area airports are still expecting limited operations. LGA in particular will remain closed until further notice due to flooding and damage on the tarmac and runways. The photo below (courtesy of CBS News) captured the standing water at the airport yesterday afternoon.

121030 Aerial view of flooding at LaGuardia (courtesy of CBS News)

As the afternoon was oddly quiet here yesterday, I took the chance to view Sandy through some of the GOES-R products at my disposal. Below is a loop of ACHA Cloud Top Heights from 121029 1745 UTC – 121030 0755 UTC (click for animation), in which the transition of Sandy from tropical to post-tropical can easily be seen. Tropical characteristics, a more banded appearance shown by the higher cloud tops (blue shades) wrapped around the eye of the storm, slowly transitioned into the more comma-like shape of a post-tropical system and more uniform cloud top heights (green shades) as the dry stratospheric air was wrapped in.

121029 1745 UTC – 121030 0755 UTC ACHA Cloud Top Heights