AT
300 Aviation Infrastructure
AT
300 Aviation Infrastructure
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Weather Prediction Models(Click on each model to link to current predictions) The AVN model
was developed primarily to aid in forecasting for aviation. The AVN gives short
range forecasts like the NGM and ETA models do, but it also forecasts well into
the medium range with forecasts every 6 hours out to 72 hours into the future.
The resolution of the AVN model is about 100 km, which is not as good as the NGM
or ETA models, but it still provides valuable insight into the future state of
the atmosphere. The AVN also tends to perform better than the other models in
certain weather situations, such as a strong low pressure area near the East
Coast of the USA. The AVN also has its own set of statistical equations that use
the AVN model output. The output from the AVN statistical equations is known as
AVN MOS. The model is run twice a day. The NGM is a short range model that forecasts variables such as
temperature at various levels of the atmosphere, amount of precipitation,
position of upper level toughs and ridges, and the position of surface high and
low pressure areas. In the nested grid model and others like it, the atmosphere
is divided into squares, or a grid, for various levels of the atmosphere. Grids
with smaller squares are "nested" inside larger ones for areas
forecasters are particularly interested in, such as North America. The smaller
the grids, the more calculations that have to be made and the bigger the
computer needed. The resolution of the NGM is about 80 kilometers. The NGM
produces forecasts every 6 hours from 0 hours to 48 hours into the future. It is
run twice a day. The ETA model is a newer model, which is very similar to the NGM model
and forecasts the same atmospheric variables. Two versions of the ETA are in
use; one with a resolution of 48 km, and the other 29 km. The grid box is much
smaller than in the NGM. This allows the ETA to give a more detailed forecast
over the USA. The ETA model was named after the ETA coordinate system, which is
a mathematical coordinate system that takes into account topographical features
such as mountains. As a result of using this coordinate system and the higher
resolution, the ETA model has a much more accurate picture of the terrain across
the USA. MOS equations have also been developed for the ETA model output. The
output from these equations is known as ETA MOS. According to Dr. Ronald
McPherson, Director of NCEP, the ETA model has outperformed all the other models
in forecasting amounts of precipitation. This noted improvement is very
important and useful for many applications such as hydrology and flood
forecasts. This model is run twice a day and looks out to 48 hours. The Rapid Update
Cycle (RUC) is an operational atmospheric prediction system comprising primarily
of a numerical forecast model and an analysis system to initialize that model.
MAPS is the research counterpart to the RUC. The RUC has been developed to serve
users needing short-range weather forecasts, including those in the US aviation
community. The MRF is one of the main models forecasters use for the medium range
time period beyond 48 hours into the future. The MRF model forecasts for the
entire northern hemisphere, unlike the national models, which only forecast for
North America. The resolution of the MRF model is about 150 km, which is far
less than the national models. The MRF is primarily used for the medium range
time period from 84 to 240 hours into the future. The MRF has its own set of
Model Output Statistics (MOS) equations known as MRF MOS. It is run once a day
in the evenings. European
Center for Medium range Weather Forecasting (ECMWF) ECMWF predicts the
behavior of the atmosphere in the medium-range up to ten days ahead. In this
time the future state of the atmosphere at any point can be influenced by
phenomena at very distant geographical locations. Many applications of
medium-range forecasting, for example ship routing, or pollution dispersion, are
not confined to limited areas of the globe. Therefore the whole atmosphere must
be included in the model - a model for medium-range forecasting must be global
and must describe the atmosphere from the earth's surface to a height of 30 km. UK
Meteorological Model (UKMET) The UKMET is one of the main models forecasters use for the medium range time period beyond 48 hours into the future. Forecasters use two European models to forecast in the medium range time period. One of two European models, this one, known as the UKMET model, was developed in the United Kingdom. The UKMET has a resolution of 75 kilometers, which is better than the MRF resolution of 150 km. The model also gives forecasts for the entire northern hemisphere like the MRF. The UKMET is run twice a day. A combination of the AVN, NGM and ETA averaged together. |
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