The 2020 Summer Experiment Has Gone Virtual!

Like so many other things in 2020, the Summer Experiment has gone virtual! While we sure do miss seeing and interacting with our partners and stakeholders in the testbed, we are excited to be able to keep the tradition going by continuing to evaluate and evolve products for the aviation community!

In order to facilitate an evaluation in the virtual realm, we are focusing on one product with a more targeted participant list. In keeping with one of the themes from recent experiments, we're focusing on convection in the next-day planning regime. For that reason our targeted participants include forecasters from the various Center Weather Service Units (CWSU) which are co-located within the FAA's Air Route Traffic Control Centers (ARTCC). These forecasters often collaborate with Aviation Weather Center (AWC) forecasters on the Traffic Flow Management Convective Forecast (TCF) creation and have a breadth of knowledge on how convection impacts planning in the National Airspace System (NAS). 

Map of CWSU coverage areas over the contiguous United States.

While we have looked at the idea of impact graphics for utilization in longer term planning for the NAS, this time we are bringing in probabilistic information to address uncertainty and start to better understand how this information can best be used in the planning environment.  For this evaluation, we are utilizing convective allowing ensemble guidance to diagnose the probability of convection exceeding TCF criteria. 

An example of the TCF Probability graphic highlighting the probability of sparse coverage of convection

Guidance imagery, depicting the probability of exceeding sparse and medium coverage TCF thresholds, will be automatically generated from two different model sources twice per day, in the early morning and early afternoon. Evaluation of the guidance by participants will help us meet the following goals

• Assess the usefulness of 24 hour summary information of TCF focused threats
• Identify optimal ways to provide, interpret, and communicate probabilistic convective information
• Assess the skillfulness of convection allowing ensemble systems for aviation focused convective forecasts

To help facilitate gathering feedback from our participants, we are once again partnering with the FAA's Aviation Weather Demonstration and Evaluation (AWDE) Services group.  Throughout the week they will help us assess the usability and utility of this product from the user's perspective via one-on-one interviews and a questionnaire. We will also have two large group discussions during which additional stakeholders will be invited to provide their perspective and input. 

Stay tuned for early results and key takeaways from the experiment!

Icing prediction using Mixing Ratios

Several of the products that we are looking at for this experiment use mixing ratios to predict regions of icing.  Both the AFWA and SREF ensembles use mixing ratio from each of the members to predict where icing will occur.

The AFWA takes a worst-case approach for explicit prediction of super-cooled liquid.  Shown below is the ensemble maximum SLD mixing ratio (shaded) with the lowest freezing level from the ensemble contoured over the top.  PIREPs for lgt-mod icing or greater have been overlaid on this forecast.'

11 Feb 00Z AFWA forecast of worst case of SLD mixing ratio and lowest freezing level height.  PIREPs are for lgt-mod icing, or greater.

Post-processing on the SREF takes a slightly different approach, looking at cloud water mixing ratio between 0 and -25 C in each member, and produces a probability that icing will occur.  PIREPs of lgt-mod icing or greater are also shown in this loop.

11 Feb 09Z SREF probability of icing.  PIREPs are for lgt-mod icing, or greater.

Convection in the Northeast.

The first week of this year's summer experiment is almost completed.  The week has certainly gone by quickly.  Today the high-resolution model evaluation and verification desk had a bit more time to put together a quick post. 

We were focused primarily on the timing and location of convection impacting the northeast.  One of the products used for this diagnostic was the probability of a lightning strike. The image below is a loop from 12Z-06Z centered over the northeast.  The field is the probability of a lightning strike within 20 nautical miles of a grid point, as calculated from the AFWA mesoscale ensemble prediction system.  This product indicated a significant lightning threat moving through Nova Scotia and Maine during this time.

AFWA probability of a lightning strike, 12Z-06Z.

Similar to the previous post, we took a look at spaghetti diagrams of the Air Force Weather Agency ensemble and the Storm Scale Ensemble of opportunity. Both ensembles indicated that the threat would primarily be cellular in nature.  The AFWA ensemble progressed the system more quickly and further east than did the SSEO.  Upon investigating the initial conditions for these ensembles, it was determined that this was likely due to the fact that all of the SSEO members were initialized off the 00Z operational NAM, while the AFWA members were initialized from 12Z and 18Z global model runs from the previous day which had the surface trough further east in earlier model runs.

The AFWA ensemble also developed more cellular convection southward, stretching across Pennsylvania. To get an idea of the potential impacts these solutions have on aviation operations, the top 25 jet routes have been plotted in each of these figures.  The AFWA solution then indicates more constraints to aviation traffic flow.

AFWA paintball plot of areas of simulated composite reflectivity >= 40 dBZ

SSEO paintball plot of areas of simulated composite reflectivity >= 40 dBZ

Convective Timing

This morning's analysis of the high-resolution ensemble models focused on the ongoing convection in the southeastern US.  One of the questions asked was when would convection clear out of the Atlanta, GA area.  One of the tools used were spaghetti/paintball plots showing the location of each of the individual members of the ensembles.  These graphics allow a quick visual of the solutions presented by the various ensemble members.

Spaghetti plot of AFWA ensemble members with composite reflectivity >= 40 dBZ, valid 17Z.

Spaghetti plot of SSEO ensemble members with composite reflectivity >= 40 dBZ, valid 17Z.

In general, more spread was observed in the AFWA ensemble than in the SSEO.  Timing was fairly good, with the location of leading edge of convection depicted in the same general area in southeast Georgia.

Radar and aircraft observations valid at 17Z.