## Wednesday, June 13, 2012

### Capacity Reduction Fields

One of the tools that has been used to diagnose the potential impacts to air traffic is the probability of airspace capacity reduction fields produced by the NCAR Research Applications Lab.  This tool uses members of the Air Force Weather Agency ensemble to diagnose the potential reduction of airspace due to weather.  This product can be thought of as a geometry problem, with each member analyzed to determine the extent to which flow into and out of a 100-km grid box will be obstructed using a mincut technique.  The capacity reduction for each of the members are then combined to produce a field that depicts the probability of a certain amount of airspace reduction, at a certain level, and in a certain direction of flow.

Note that because this problem simply uses the geometry of the grid to determine capacity reduction, it does not take into account planned or actual traffic.
Thus, using a simple example, if the number of planes that can fly through a particular portion of airspace over an hour is 80, and the demand for this hour is only 25 aircraft, a 50% reduction of airspace capacity (in the geometric sense, as is diagnosed in these products) will not impact aviation operations through this region.

Shown here are fields of 50% reduction in airspace capacity at FL300 (30,000 ft).  This shows the proportion of AFWA members that show a blockage of at least 50% for that particular 100-km grid box.  These are computed for two directions of flow: east-to-west/west-to-east, and north-to-south/south-to-north.  To get an idea of how these fields are derived, plots of the individual members are shown below the capacity reduction fields.

The first set of images is valid at 1700, when the AFWA members are capturing the system off the Atlantic coast.  The first frame depicts the reduction in the north-south direction, with the second frame depicting the east-west capacity reduction.  Because the line is oriented southwest-to-northeast fashion, the difference between the two directions is not as pronounced.  Another contribution to this similarity is the scale at which these fields are produced.
 Probability of 50% reduction of FL300 air capacity in North-South direction at 1700 UTC.
 Probability of 50% reduction of FL300 air capacity in East-West direction at 1700 UTC.
 AFWA ensemble members showing simulated composite reflectivity >= 40 dBZ at 1700 UTC.

The next three images are valid at 2000 UTC, after several members of the AFWA are developing convection along the coastal sea breeze.  The difference between the two orientations is a bit more pronounced in this case, especially along the South Carolina coast.  The capacity reduction product indicates that the flow will face a greater (geometric) constraint in the north-south direction than in the east-west direction, which can be seen by looking at the individual solutions in the third image.   Along the Florida and Georgia Atlantic coast there is more reduction in the east-west direction due to the orientation of the convection in this region.
 Probability of 50% reduction of FL300 air capacity in North-South direction at 2000 UTC.
 Probability of 50% reduction of FL300 air capacity in East-West direction at 2000 UTC.
 AFWA ensemble members showing simulated composite reflectivity >= 40 dBZ at 2000 UTC.

## Tuesday, June 12, 2012

### Convective Initiation and NCAR's Large-Scale Convective Storms product

Week two of the Aviation Weather Testbed experiment is underway, with visitors and AWC personnel working together to produce experimental Aviation Weather Statements, examine new GOES-R data, and evaluate new high resolution ensemble forecast models.

A well known problem in convection forecasting (and perhaps, by argument, the most important) is determining the location and timing of convective initiation in the atmosphere. High resolution forecast models struggle with initiation in environments that are not strongly forced, especially in conditions where a broad area of instability exists without well-observed atmospheric structures (boundary layer convergence, etc.) So, how does a meteorologist address this problem, when faced with producing a decision support tool to help aviation traffic planners determine where storms will affect the National Airspace System? The answer is not easy, and is the reason why the Aviation Weather Testbed works with academic partners that are producing content that helps aid in determining the liklihood of convection potential.

The image below is created from NCAR's Large-Scale Convective Storms product, and depicts the liklihood that a large scale convective storm will initiate at a given location. Of concern in this image is the high probability that a convective system will initiate around 19Z near the western Pennsylvania area, which could create a significant impact to the New York region airports later in the day.

The LCS product forecasts that after initiation, the storm system will move into central Pennsylvania and West Virginia, an area in the NAS that is especially vulnerable to creating delays given the jet routes there that direct traffic to the New England region:

New tools like the LCS product are evaluated daily by AWT experiment participants, and illustrates one example of new and emerging data sets that researchers are testing and refining to help forecasters with the difficult problem of forecasting convection for the NAS.

## Friday, June 8, 2012

### AWT GOES-R Blog

Please be sure to check out the Aviation Weather Testbed GOES-R Blog.  They have a great demonstration of a variety of GOES-R proxy products in action.  Updates are also linked on the right sidebar.

### 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

## Monday, June 4, 2012

### 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.

## Sunday, June 3, 2012

### 2012 Summer Experiment Preview

The 2012 Aviation Weather Tested summer experiments starts Monday morning and runs for two weeks.  We are very excited to welcome everyone who is participating.  We again have a large group of participants including National Weather Service forecasters, airline operators, Federal Aviation Administration personnel, researchers from industry and Universities, the Air Force Weather Agency, and international visitors.

This year we will be running two desks focused on traffic flow management and the production of an Aviation Weather Statement (AWS).  This product will be generated to support the expansion of Aviation Weather Center operations into the Air Traffic Control System Command Center (ATCSCC) and will be a demonstration of operational bridging.  Two desks will be tasked with producing this product, with each desk testing a different generation mechanism.

This year the AWT will be examining a wide array of products supporting the GOES-R program and evaluating how these may be used to support aviation weather forecast, warning, and planning operations.  To support this evaluation, one desk will be dedicated to using proxy products generated from current observational platforms and simulated products generated from high-resolution numerical weather prediction models.

The fourth desk of the experiment will be tasked with an in-depth examination of operational and experimental high-resolution numerical forecast models in support of aviation operations.  One important part of this process will be to examine how the confidence in numerical forecasts is can be conveyed in automated and human-generated forecasts.  This desk will also be comparing how well objective verification metrics correspond to the subjective evaluation from a panel of forecasters, forecast users, and operators.

For more information, please visit the 2012 Spring Experiment web page.  We look forward to working with those of you in attendance during the next two weeks.