Day 4: Afternoon Transportation Briefing

As was the case the past two days, we presented an afternoon transportation briefing in collaboration with HPC.  The focus was a Day 2 forecast, valid 00Z Feb 16th - 00Z Feb 17th.  The AWC was again responsible for forecasting the aviation threats of icing, turbulence, and IFR conditions.

Today the forecaster chose to show the evolution of conditions by drawing five graphics valid across the period, which is presented in the loop below.

Transportation briefing graphic valid 00Z Feb 16 - 00Z Feb 17.  IFR conditions are outlined by the red solid line, Icing by the green dashed line, and turbulence by the yellow dashed line.

Turbulence Guidance

This post will highlight some of the turbulence guidance being used and evaluated in the testbed during the experiment.  The valid times are 13 Feb 21Z - 14 Feb 09Z.

The first two images below are guidance that is available on our operations floor.  To get a general idea of the pattern, the 300 hPa heights, winds and isotachs are plotted.  The second image shows the Ellrod-Knox Turbulence Index for the same period, which is highlighting a region of enhanced turbulence along the east coast developing along the shear zones of the ridge.

13 Feb 12Z NAM forecast of 300 hPa heights and winds.

13 Feb 12Z NAM forecast of 300-400 hPa Ellrod-Knox Turbulence Index.

For the experiment, we have been looking at several different high-resolution forecasts of turbulence.  The first is a probabilistic forecast of turbulence from the AFWA ensemble between 25,000 and 30,000 feet.  The second is an explicit prediction of Turbulent Kinetic Energy (TKE) from the WRF-NMM run at 00Z and 12Z for the Storm Prediction Center.  Plotted is the maximum value over the previous hour in the layer between 200 and 500 hPa.

13 Feb 00Z AFWA forecast of probability of turbulence for FL250-300.

13 Feb 12Z SPC WRF-NMM forecast of hourly max TKE between 200-500 hPa.

Looking at these different solutions, all have the ribbon of turbulence along the east coast jet, but the location of the maximum differs depending on the predictor.  A loop of water vapor imagery for this period is shown below.  Overlaid on this loop are automated aircraft observations of Eddy Dissipation Rate (EDR), which are an objective measure of turbulent eddies in the atmosphere, as well as subjective Pilot Reports (PIREPs).  Toward the end of the period, a Turbulence SIGMET was issued off the New England coast.

GOES-East Water vapor imagery with EDR observations from aircraft and Turbulence SIGMETs.

Day 4 of the Winter Weather Experiment

We have a smaller group in the Testbed today, as some our external visitors have travelled back to their primary workplace.  We had participants from NTSB, Lockheed Martin, NOAA GSD, NCAR, NWS Forecast Offices, NASA, as well as our local AWC forecasters.  Lockheed presented on their briefing operations, giving the forecast and development staff here an insight into how AWC products are used to brief GA and corporate pilots.
Today, the collaboration with HPC will be focussed on Day 2 (00Z Feb 16 - 00Z Feb 17Z), due to low weather impacts to aviation operations in the Day 1 time frame.

Winter Weather Experiment Photos

We have posted a photo album with pictures from the 2013 on the Aviation Weather Center Facebook account.  If you would like to follow us, please visit the AWC Facebook Page.

Experimental Mountain Obsuration Guidance

One of the products that is being tested in the winter experiment is a probabilistic mountain obscuration product based on the Short Range Ensemble Forecasting System (SREF).  The SIERRA G-AIRMET package includes a forecast IFR conditions due to ceiling and visibility, as well as a forecast of extensive mountain obscuration.  The image below depicts
the mountainous regions for which obscuration forecasts are produced.  As you would expect the the major mountain ranges in the US are depicted, but forecasts are also produced for smaller ranges like the Black Hills and the Ozarks.

Image depicting regions of mountains

Automated guidance based on the SREF was developed, using a 40km horizontal grid.  A USGS Digital Elevation Model (DEM) with a 30-second resolution (~0.9km) was used to defined mountains on this 40km grid.  A grid box is mountainous if the elevation within the box varies by at least 1000 feet.  Mountain obscuration is determined for each SREF member.  If a forecast ceiling for a grid box is lower than the highest elevation from the DEM, that point is defined as obscured for that particular member.  Probabilities are then constructed from the percent of members that indicated obscuration at that grid point.

Below is a loop of the mountain obscuration forecast from the 09Z SREF run issued today.  Probabilities are shaded starting at 40%.  Also shown are experimental mountain obscuration G-AIRMETs issued in today's Winter Experiment.

Probability of Mountain Obscuration from the 09Z SREF forecast on 13 Feb.  Overlaid are the experimental mountain obscuration G-AIRMETs issued by the testbed forecaster.

Day 3: Afternoon Transportation Briefing

Similar to yesterday, we participated in the afternoon transportation transportation in collaboration with HPC.  In producing today's graphic, the forecaster at the experimental National Aviation Meteorologist desk collaborated with each of the area forecast desks here in the aviation weather testbed.  Again, the focus of the graphic produced by AWC was on aviation threats.  This graphic helped to supplement the precipitation focus of the HPC briefing graphic.

Day 3 of the Winter Weather Experiment

Welcome back to Day 3 of the Aviation Winter Weather Experiment! Yesterday was a successful day in the testbed with many discussions among the participants,  collaborative weather briefing with HPC, and a very informative presentaton by NTSB. Today we are expecting a continuation of great discussions on current weather events, experimental data sets, and product displays.  We will conduct another collaborative weather briefing with HPC and have a presentation by Lockheed Martin.