FAAO 7900.5 PDF

FAA Form , Directive Feedback Information, is available for this Well, they might have that corrected when the Z is released. Find the most up-to-date version of FAA at Engineering Find the most up-to-date version of FO JO D at Engineering

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In a February 7 article “A likely record, but experts will get back to us” Frank Roylance wrote:. Those rules say the observer must allow snow to fall on an official ‘snow board’ for six hours, then wipe it clear and repeat the procedure every six hours until the snow ends.

This statement is inaccurate and misleading in that it gives the impression that the weather observers contractors at Baltimore-Washington Thurgood Marshall Airport did not accurately perform their job in measuring snowfall.

The weather observers at BWI have a combined experience on the job of well over years of service with some of the individual observers having worked more than 30 years in the field.

These workers know well the correct procedures to follow regarding snow measurement and followed them during the time period in question.

Our company employs the weather observers at BWI. The guidance is provided in the FAA publication The relevant paragraph states:.

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There is no further guidance given in the FAA manual In fact, the FAA manual Therefore, one can fwao as many times as needed during a six-hour period, provided the totals for all snowfall during the period are given.

Moreover, the FAA requires observers to keep track of the snow increasing every hour and requires hourly measurements.

The weather observers use panels of wood or plastic called snow boards on which snow accumulates to do their measurements. Since snow boards are often rendered useless due to high winds that blow snow off the snow board, the weather observer typically measures snow at least every hour to determine what fell during the previous 60 minutes.

The FAA manual These procedures were followed at BWI. In fact even the NWS in its snow training program declares that during windy conditions snow must be measured more often to compensate for wind loss.

Sun mischaracterizes snow measurement protocol

It is therefore inaccurate to claim that in every instance the NWS policy states that snow must be measured only every six hours. During the dates of the storm over February 5 and 6, BWI reported a snow depth of 24 inches.

7090.5 their geographic proximity, the snow they reported to have fallen at each location seem to coincide. IAD had 20 inches of snowfall and had a snow depth of 21 inches of snow on the ground after the storm. They had 1 inch of snow on the ground before the storm, a net gain of 20 inches.

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Where to find US airport weather Service Levels? – Aviation Stack Exchange

The totals at IAD which indicate that they added 20 inches of snow depth for 20 inches of snowfall seem much more consistent than the NWS Sterling that reported 32 inches of snowfall but only an increase of snow depth of 21 inches. It is therefore odd that the NWS would also accuse the weather observers at IAD of providing erroneous snow fall measurements during that storm because they were measuring the snowfall more often than once every six hours because the NWS snow training guidance states that hourly snow measurements fazo erroneously increase the estimated snowfall, not decrease them.

In a February 7 article “A likely record, but experts will get back to us” Frank Roylance wrote: The relevant paragraph states: