Tuesday, February 19, 2013

Low Level WInd Shear Probabilities

We are evaluating two ensemble forecasts of low level wind shear (LLWS). LLWS is one of the hazards that are forecast as part of our turbulence package.  Both the AFWA and SREF have been post-processed to produce a probabilistic forecast of low level (0-2000 feet AGL) greater than 30kts.

09Z SREF run on 19 Feb, LLWS probabilities between 21Z Feb 19 - 09Z Feb 21.
12Z AFWA run on 19 Feb, LLWS probabilities between 21Z Feb 19 - 09Z Feb 21.

Visualization of Turbulence Layers

The AWC produces the Graphical Turbulence Guidance as part of its suite of automated supplemental aviation forecast products.  A forecast of eddy dissipation rate is produced at 21 different horizontal flight levels, and is typically visualized either on these 21 flight levels or as a composite, which is the maximum value in the atmospheric column.
15 GTG forecast from 19 Feb, valid at 21Z.  Loop starts at the bottom of the atmosphere and shows the EDR values at each vertical level between FL100 and FL450.
15 GTG forecast from 19 Feb, valid at 21Z.  This composite chart shows the maximum value between FL100 and FL450.
Only viewing the GTG product in this manner necessitates an analysis of each of the vertical levels to ascertain the vertical characteristics of where the turbulence is forecast.  Since turbulence forecasts at the AWC are issued for high-level and low-level turbulence, which are split at 18,000 ft MSL.  Shown below are the probability of moderate or greater (MOG) turbulence above, and below FL180, respectively.  Probability in this application is defined as the percent of layers with MOG turb.
Probability of Moderate or Greater Turbulence above FL180. The probability is defined as the percentage of layers that have moderate or greater.
Probability of Moderate or Greater Turbulence below FL180.  The probability is defined as the percentage of layers that have moderate or greater.
An additional visualization that is being tested is the base and tops of moderate turbulence.  This is computed using a top-down (bottom-up) search for the first level of moderate or greater turbulence.  Un-shaded portions of these plots are regions where forecast turbulence does not reach a moderate intensity.  This can provide a quick view of the vertical extent of turbulence, although there may be layers between the tops and bases that do not reach a moderate intensity.
Bases of Moderate or Greater Turbulence.

Tops of Moderate or Greater Turbulence.

Pattern Recognition in Turbulence Guidance

Part of forecasting the weather is being able to recognize patterns in meteorological features.  Below is an image from the today's 06Z issuance of the Global Graphical Turbulence Guidance produced by NCAR.  Any experienced forecaster will immediately recognize this as Sad Turbulence.
Sad Turbulence

Week 2 of the Winter Weather Experiement

After the 3-day President's Day weekend, we are kicking off the second week of the Winter Experiment today.  Visitors from the National Center for Atmospheric Research,  NWS Office of Science and Technology, the Japan Meteorological Agency are in attendance this week and we have a couple of presentations and round-table discussions lined up for the afternoons throughout the week.

Friday, February 15, 2013

Day 5: Afternoon Transportation Briefing

The forecaster for today's collaborative briefing with HPC decided to break up the briefing into hazard and again show the separate valid times.  The forecast period was 00Z Feb 16 - 00Z Feb 17.  The three hazard graphics are shown below.

This will be the last collaborative briefing with HPC, since their Winter Experiment ends today.
IFR Forecast for 00Z Feb 16 - 00Z Feb 17.
Turbulence Forecast for 00Z Feb 16 - 00Z Feb 17.
Icing Forecast for 00Z Feb 16 - 00Z Feb 17.

Day 5 of the Winter Weather Experiment

Today marks the midway point of the first Aviation Weather Testbed Winter Experiment.  NCAR presented recent developments in their icing research to the experiment participants and other AWC staff.  As with the other days, we reviewed the forecasts produced the previous day.  We primarily focused on the turbulence the National Airspace System (NAS) experienced yesterday.

Since Monday next week is President's Day,  the testbed will be full again on Tuesday and will continue through next Friday.

Communicating Impact

An important part of producing a forecast for the public is communicating the impacts that the weather will have.  As part of the HPC afternoon transportation briefing, the impact graphics produced by HPC and AWC forecasters is critiqued by human factors researchers.  They provide feedback on how well the graphics communicated impacts important to emergency managers and air traffic decision makers.

One of the pieces of feedback offered by these communication experts on yesterday's graphic was that when multiple regions of Instrument Flight Rules (IFR) were depicted, it was somewhat difficult to tell which side of the red line was supposed to be IFR.  This was especially the case when these regions were close to each other.  The first image below is the original briefing graphic, where the "IFR" label was placed on the side of the red contours where IFR was expected.  Adding a shading to the appropriate side of the contour reduced confusion and provides higher "glance value" and communicated this information more quickly.

Original briefing graphic.
Updated briefing graphic with shading indicating regions where IFR was forecast.

Thursday, February 14, 2013

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.

Wednesday, February 13, 2013

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.

Tuesday, February 12, 2013

Day 2: Afternoon Transportation Briefing

As part of the first week of the 2013 Winter Weather Experiment, the Aviation Weather Testbed is working with the HPC Winter Experiment to produce a collaborative transportation briefing.
In addition to collaboration with the HPC, this forecast was also produced with collaborations involving NWS WFO forecasters and the experimental Global Graphics forecasting desk that is part of the experiment.

One of the AWC National Aviation Meteorologists (stationed at the FAA System Command Center) is participating in the HPC Experiment this week and is focusing on communicating precipitation types and timing.  The graphic below was produced by an AWC forecaster in Kansas City and focuses on the icing, turbulence, and IFR conditions associated with a system that is forecast to impact the east coast on Feb 14-15.
Transportation briefing graphic valid 14 Feb 00Z - 15 Feb 00Z.  Depiction of IFR, icing, turbulence, and wind threats associated with forecast cyclone.

One of the automated tools that is available to forecasters and air traffic planners is the Aviation Winter Weather Dashboard.  The dashboard translates winter weather as forecast by the SREF into terminal impacts based on how well the airport can handle certain winter weather events.  Below is a snapshot of the dashboard showing terminal impacts in the northeast as forecast by the 09Z SREF on 12 February.

Aviation Winter Weather Dashboard showing terminals in the Northeast.  Forecast from the 09Z SREF on 12 Feb.

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.

IFR Verification

As a follow-up to yesterday's post concerning probabilistic flight rule prediction, here are some quick verification images.  For the C&V prediction, the forecast period is 21Z - 09Z.

Each image contains the METAR observations of flight category overlaid on the gridded data set.  The first gridded data set is an analysis of observed ceiling and visibility conditions, the National Ceiling and Visibility Analysis (NCVA).  Hourly data is show along with the METARs that went into this analysis.

NCVA Field and METAR flight category for 21Z 11 Feb - 09Z 12 Feb.
The primary forecast concern in this area was the lifting of the ceilings, bringing terminals out of IFR conditions.  The dataset shown below is the GFS-LAMP IFR conditions.  Regions shaded in green are where the 18Z GFS-LAMP run from 11 Feb is predicting IFR conditions.  It clears the IFR conditions fairly well in PA/NJ/NY/CT, but keeps DL/MD/VA in IFR conditions too long.

11 Feb 18Z GFS-LAMP forecast valid same period as NCVA.
Additionally, the SREF and AFWA probability of flight category as highlighted in yesterday's post is show below.  The SREF is the 09Z run from Feb 11, and the AFWA is the 00Z run from the same day.  Only the MVFR and IFR conditions are shown in each of these products. The SREF forecast does not seem to discriminate well between MVFR and IFR conditions (all or nothing) and clears the IFR conditions along the northeast coast fairly well.  The AFWA forecast tends to clear the IFR conditions to quickly along the northeast coast.

Another feature of both of these forecast is the forecast areas of IFR around the Great Lakes region that did not verify.  MVFR conditions were observed in MI and NWRN OH.  In the SREF this area is especially overdone and we are again seeing the issues that the SREF has discriminating between MFVR and IFR conditions.  The are in the AFWA is also overdone, with IFR conditions forecast in PA where only MVFR was observed.

11 Feb 09Z SREF forecast valid same period as NCVA.
11 Feb 00Z AFWA forecast valid same period as NCVA.

Day 2 of the Winter Weather Experiment

Good morning and welcome to Day 2 of the 2013 Aviation Winter Weather Experiment. We have a few new faces in the room today. Visitors from NTSB and the local WFO joined our other visitors from AFWA, NCAR, GSD, NASA, and Lockheed Martin.

We have already had a busy morning of assessment and verification of yesterday's model and human forecasts. Check out the IFR Verification blog for additional information. Additionally, morning weather briefings set the stage for today's hazards and focus regions. The ceiling and visibility desk forecasters are looking in the Pacific Northwest for low ceilings and will focus on the South from the Houston and Fort Worth regions shifting towards Memphis and Atlanta as the day progresses.  The turbulence desk will focus along the east coast/Atlantic seaboard with low level wind shear presenting a problem along the GA and SC coast and low turbulence over PA. Forecasters will also keep an eye over soutwest Texas where lowel level turbulence will likely be a hazard today. Finally, the icing desk will be focusing on developing storm over the central plains and icing hazards in the NE from West VA northeastward up to Maine.

Monday, February 11, 2013

Ensemble Prediction of Flight Rules

One of the things being explored in the Winter Weather Experiment is the use of mesoscale and high-resolution ensembles for prediction of ceiling and visibility.  The two primary ensembles being explored for this purpose are the Short Range Ensemble Forecasting (SREF) System and the Air Force Weather Agency (AFWA) mesoscale ensemble.

The SREF is composed of 21 ensemble members with post-processed output on a ~16km horizontal resolution, while the AFWA ensemble has 10 members run at a ~4km horizontal resolution.  Each individual member is obtained by the Aviation Weather Center where we perform additional analysis that is not done in the basic ensemble post-processing.

Each of the individual member solutions contains a prediction of ceiling and visibility, for which ensemble statistics are computed.  Additionally, the flight rule category is computed for each ensemble member, from which the probability of the flight category can be determined.

These probabilities for the time period between 21Z Feb 11 - 09Z Feb 12 are shown for the AFWA and the SREF below.  Note that these probabilities are not calibrated and weight each of the ensemble members equally.  Both the weighting of the members and the calibration will need to be explored in order to improve the reliability of these forecasts (see: Reliability and Resolution). 
Probability of Flight Rules as predicted by the 00Z AFWA from 11 Feb 2013.  Valid 21Z 11 Feb - 09Z Feb 12.  MVFR, IFR, and LIFR conditions are shaded in blue, red, and yellow, respectively, shaded starting at 40%.
Probability of Flight Rules as predicted by the 03Z SREF from 11 Feb 2013.  Valid 21Z 11 Feb - 09Z Feb 12.  MVFR, IFR, and LIFR conditions are shaded in blue, red, and yellow, respectively, shaded starting at 40%.

2013 Winter Weather Experiment Kick-Off

Good morning! The 2013 Aviation Winter Weather Experiment has officially started. With visitors from NCAR, AFWA, Lockheed Martin and AWC forecasters, we have a full testbed! Forecasters will use a wide range of operational and experimental products as guidance when issuing their products. Cutting-edge GOES-R products, high-resolution deterministic models and ensembles, assessment tools, and displays are being debuted in the testbed over the next couple of weeks for the forecasters to evaluate and provide feedback for the developers.  Please come see us in the testbed if you can or check back here for more information.

Thursday, February 7, 2013

Winter Weather Experiment

The first ever Aviation Winter Weather Experiment will kick-off on Monday, February 11th at 8:00 am in the Aviation Weather Testbed! Please visit the 2013 Winter Weather Experiment webpage for information on data sets, displays, and tools that will be utilized during the experiment.