Why your smartphone says it’s sunny Tuesday, when it’s not | Latest Headlines:

It’s 1:00 pm Thursday and if you look at your generic phone app, you’ll see that it was “mostly sunny” or “fair” in the region.

This is, obviously, incorrect. In fact, this is one of the many reasons why a living, breathing, in-person Meteorologist will always have been needed to explain and forecast the weather.

Your weather app or website (which we hope is ours even though it, too, is saying it is sunny) is correct, but not truthful. To show you the light (or, dimness), we need to do a little digging into the way observations are coded. That means, a dive into: The Federal Meteorological Handbook No. 1.







Clouds are overhead South Jersey on June 7, with white, blue and green colors on top of the state. So, why does our smartphone say it is sunny?


Joe Martucci:



Most airports around the country have a weather station. These weather stations report on a variety of factors like temperatures, winds, dew point, rainfall and sky cover. These are then put into a code, called METAR, short for Meteorological Terminal Aviation Routine Weather Report. The code is used to help shorten what would otherwise be large amounts of information.

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However, weather stations come in all shapes and sizes. Most stations are automated with larger airports having their own weather observer on site. For the most part, you will not notice the difference. All report temperatures, dew points, winds and rainfall the same. There are two main exceptions, though.

Automated stations do not measure the snow that is falling (that is topic for another story), places with weather observers do. When it comes to sky cover, both automated and staffed stations report it. Many times, it is with something called a celiometer, which uses a laser to help measure height. However, they do so differently.

Let us go back to: The Federal Meteorological Handbook No. 1. The book has the answer. To quote,

“Automated stations shall have the ability to evaluate sky condition from the surface to at least 12,000 feet. Observers at manual stations shall evaluate all clouds visible; the 12,000 foot restriction shall not apply.”

Put another way, manual stations must record all layers that are present, up to where it becomes overcast. Automatic stations only records clouds up to 12,000 feet.







Sky Clear:

According to the Federal Meteorological Handbook No. 1, stations that do not have a human observer present, like Atlantic City International Airport does on Tuesday, will use CLR when no clouds are present * below * 12,000 feet. At Philadelphia International Airport, which does have an observer present, he / she is reporting a cloudy sky, but at 16,000 feet, above the threshold used. Therefore, South Jersey is “clear”.


Joe Martucci:



Philadelphia International Airport has a staffed weather observer there nearly 24/7. Atlantic City International Airport does not have one, though air traffic control can alter the observations in extreme events. Like Thursday, and most days, the automatic obversions were used.

So, if you went on say, the National Weather Service website, where your app or website receives the data from and typed in Philadelphia, you would see this.







PHL.JPG:


National Weather Service:


On the other hand if you went to AC Airport, or anywhere near the airport, you would see this.







ACY.JPG:


National Weather Service:


A mostly cloudy layer of clouds 21,000 and 28,000 feet high in Philadelphia at the 11:54 am observation. Your phone in Philadelphia accurately says it’s cloudy, while those in southeastern New Jersey say it’s fairly sunny.

So, because there is no weather observer at ACY Wednesday, tens of thousands of people scratch their heads wondering why the current conditions are wrong. It is not the National Weather Service’s fault.

Turns out, you just need to ask a Meteorologist to find out the truth.

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