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EZTip No. 4 - Cloud depiction on the EZRoute Profile

The EZWxBrief progressive app provides the capability to see a depiction of clouds on the EZRoute Profile and EZAirport Meteogram views. For ease of discussion, both of these views utilize the same technique in how the presence or absence of clouds are determined. But in this EZTip, we'll only utilize the EZRoute Profile view.


First and foremost, determining the presence of clouds along a proposed route of flight is incredibly difficult if not fundamentally impossible. So a probabilistic approach using numerical weather prediction models is required. Many of the heavyweight aviation apps on the market that also employ a route profile view will determine if clouds exist by utilizing a rudimentary relativity humidity scheme. In general, this is a horrible approach to determine the presence of absence of clouds and is unreliable especially for cold clouds (clouds at temperatures below -12°C). EZWxBrief, on the other hand, utilizes what is referred to as "cloud fractions" that are taken from several forecast models to determine the presence or absence of clouds along the proposed route.


Without getting into the weeds of the very complex algorithm employed by EZWxBrief, here's a high level view of how it is done. Once each hour, the EZWxBrief data server pulls a fresh new version of the numerical weather prediction data from several high resolution models. When a user activates a route, it will do a georeferenced lookup and pull all necessary model data that is within a 50 mile corridor along the route (25 miles on each side). Essentially, at the departure airport and every 5 km along the route up to the destination airport, it attempts to find at most four primary cloud layers aloft using a cloud fractions scheme. It may find no cloud layers or up to four layers.

Using the cloud fractions scheme mentioned above along with the icing and ceiling algorithm (for consistency) it determines if the sky is clear or if there is indeed some cloud coverage up to 50,000 feet. If there are no cloud layers found, the sky is shown to be clear above that point. If there's a single cloud layer, then it will determine the cloud coverage (few, scattered, broken or overcast) and depth and plot that on the route profile as a white or gray rectangle at that location and altitude in the main viewport. White is used for broken or overcast and gray is for few or scattered cloud coverage. Taller rectang