Forecasting the weather for the New Mexico television market is difficult. The large size of the region (almost all of New Mexico and parts of Arizona and Colorado), as well as the varied terrain provide a great challenge. According to Nielsen Media Research, more than 600,000 TV-watching homes are included in this large viewing area. But for one 9-day event, even more eyes turn to the television stations to get the weather forecast. The International Albuquerque Balloon Fiesta draws nearly 750,000 people to the state and city each year. The largest ballooning event in the world attracts 700 balloons, balloon pilots and balloon enthusiasts from around the world. During that time the main focus is on weather at sunrise. Will the balloons be able to launch? Also, where do the tourists and New Mexicans need to go to see the balloons? These are additional challenges for those forecasting the weather during the Fiesta, held in early October. The accuracy of weather forecasts during this time can affect the safety of the balloonists, the tourists length of stay in the state and the money the Fiesta brings in. The one thing everyone wants to hear is that the famous ‘Albuquerque Box’ will be working every morning.
The Albuquerque Box is a weather phenomenon where the lowest winds are moving in one direction and the higher level winds are moving in another. More specifically, in a perfect example of the Albuquerque Box, the high winds are from the south while the low winds are from the north. This is beneficial to ballooning because then the balloon can take off and land in almost exactly the same spot. Balloon pilots do not have a way to steer their hot air balloons. While they can control where the balloon flies vertically (by heating the air in the balloon to go higher), they rely on the wind to determine their direction. The Albuquerque Box allows pilots to better control where they fly and where they land. Since the winds are blowing from the north in the lower levels, pilots rise just a little and fly towards the south. Then they can ascend higher by lighting the burner and warming the air inside the balloon envelope, catch the winds from the south and fly back to where they took off, to land. When the Albuquerque Box is working, tourists can then stay in one spot and watch the balloon launch, drift away, then drift back and land all from the same location.
Albuquerque’s location is crucial to even the possibility of the Box forming. The city sits in the Rio Grande Valley between the Sandia Mountains and the West Mesa. The Albuquerque Box is “essentially a valley wind pattern that develops under certain ‘stable’ conditions.” Temperature, wind and moisture all factor into creating this unique weather situation. Temperature is important because cooler air is more dense than warm air and the air that is more dense sinks below the less dense air. Albuquerque is in a desert so there is usually a large difference between daytime highs and daytime lows. The earth always emits longwave radiation but during the day, solar radiation warms the earth bringing in more energy than is lost, creating a net energy gain. Radiational cooling causes the air near the ground to cool off at night and since, at night there is no solar radiation, there is a net energy loss. This causes the air to cool off at night.
Cool air is more dense than warm air. In Albuquerque, the cooler air moves down the side of the Sandia Mountains and gathers in the valley, creating a shallow layer of cool air no more than a few hundred feet in depth. In the early morning as the sun comes up, this wind generally flows southward down the Rio Grande Valley because then the wind is also flowing from a higher elevation in the north to a lower elevation in the south. This forms the lower level wind for the Albuquerque Box.
Meanwhile, the air above will be warmer. This temperature situation, necessary for the formation of the Albuquerque Box is known as a temperature inversion. A temperature inversion is when there is a layer of the atmosphere where temperature increases with height. As a weather forecaster that is something to look for when predicting if the Albuquerque Box will come into play during Balloon Fiesta. Be sure to look at the temperature changes with height in the atmosphere. The warmer air above is less dense and can move in another direction than the lower level air.
Again, a perfect Albuquerque Box will have the higher wind moving in the opposite direction, meaning it would be a south wind blowing towards the north. So the forecaster must look at the change in wind direction with height. This is known as vertical directional shear, defines as significant change of wind direction with height. Often, weather forecasters may look at upper level wind direction for the development of severe storms or tornados. Even then, forecasters don’t usually mention the direction of the higher winds in their television broadcast or go into it in great detail, probably because they believe the average viewer doesn’t care, especially if there is not a threat of severe weather. But forecasting for balloon pilots is different. These pilots care very much about the change in wind direction with height and many balloon enthusiasts understand how this will affect the balloon flights and the formation of the Albuquerque Box. The vertical directional shear should be a large part of every Balloon Fiesta forecast.
Moisture can also affect whether the Albuquerque Box will ever develop. Moist air is less dense than dry air at the same temperature. Relative humidity is a measure of how close the air is to saturation while dewpoint is a measure of the quantity of moisture in the air. Forecasting during Balloon Fiesta means watching the humidity and the dewpoint. The higher the humidity or the higher the dewpoint, the more moisture is in the air and the less dense that air will be. The moist air can disrupt the temperature inversion and cause the Box never to develop or to fall apart quickly.
In order for the Albuquerque Box to form, these weather conditions must all happen at the same time. In fact, this combination of temperature inversion, vertical directional shear and lack of moisture doesn’t happen too often. According to one source, “a local study found that on average the ‘box’ circulation occurs 30 percent of the time in early October.” This means for the nine-day Balloon Fiesta, the Albuquerque Box will probably be working only about three of those days. It’s important to remember even on those days when the Box is in effect, it doesn’t last long. Once the sun comes up, the solar radiation starts heating the ground and also the air. The same increase in temperature that allows Balloon Fiesta tourists to remove their jackets, starts to break down the temperature inversion and effectively ruin the Albuquerque Box. That’s why forecasters during Balloon Fiesta also must keep in mind when the sun will come up and how quickly the temperature will warm. Balloon pilots plan their launch so they can ride the Albuquerque Box before it dissolves.
Forecasting in Albuquerque during Balloon Fiesta means focusing on certain weather conditions. The forecaster must try to determine whether the Albuquerque Box will form each morning of the 9-day event. They need to look for a temperature inversion with cooler air at the surface and warmer air above. They also need to look for vertical directional shear, or a change in wind direction with height. Preferably the wind at the surface will be a north wind with higher winds from the south. The third condition to look for is a lack of moisture. Lower dewpoints and lower humidity levels will increase the chance that the Albuquerque Box will develop. Forecaster, as well as balloon pilots and enthusiasts, need to keep in mind that this combination does not happen often to create the Albuquerque Box.
Forecasting whether the Albuquerque Box will occur or not is extremely important to balloon pilots, tourists and the entire business community that depends on a successful Balloon Fiesta to bring money to the area. Pilots plan their balloon flights based on the forecasts and the Fiesta organizers plan the entire event (whether to allow balloons to launch, how to do it safely, etc.) based on those forecasts. This is a difficult event to forecast because even when it does happen, it doesn’t last for very long. Also, it is such a specialized event to the Albuquerque area and especially important during this 9-day event, there doesn’t appear to be all that much research or expert opinion about it. But for that short time in this growing city, knowing whether the Albuquerque Box will form is crucial and there is a way to better forecast for it. Focusing on the most important pieces of information will lead to the highest level of accuracy. Be sure to study temperature and wind changes with height, moisture and the time of sun rise. Forecasting isn’t a perfect science but by knowing the important elements that will lead to the formation of the Albuquerque Box, a forecaster can increase their chances of getting it right.
Appendix & Endnotes
Example of the lower winds blowing down the valley and a chart showing the
temperature inversion and vertical directional shear needed to create the Albuquerque
Box. Both are from http://www.srh.noaa.gov/abq/feature/abq-box.htm.