Partly Sunny or Partly Cloudy?

Posted: November 30, 2009 in ALL TOPICS, WEATHER WORDS
Amy Freeze at Soldier Field
Amy Freeze at Soldier Field

Partly Sunny or Partly Cloudy 

Talking about the weather is not about how you look at life – the cup half empty or the cup half full?   It’s not an optimistic or a pessimistic view of how many clouds are out there… describing details of cloud is not about the forecaster’s mood!  There is a way to be clear when using Partly Sunny versus Partly Cloudy.  For current conditions, I use the terms “Partly Sunny” during the day, and “Partly Cloudy” at night… obviously it will never be Partly Sunny when describing night conditions.  The way sky conditions are described  in the National Weather Service are defined according to specific parameters.

From the National Weather Service Operations Manual, Chapter C-11 under Zone Forecast Guidelines and Procedures:
DAY                         NIGHT/DAY                       SKY                                                                                                                                                                         Cloudy                      Cloudy                                  8/8 opaque clouds
Mostly Cloudy      Mostly Cloudy                   6/8 – 7/8 opaque clouds
Partly Sunny          Partly Cloudy                    3/8 – 5/8 opaque clouds
Mostly Sunny         Mostly Clear                      1/8 – 2/8 opaque clouds
Sunny                         Clear                                     0/8 opaque* clouds* opaque means that an observer can not see through the clouds; the sun, moon , stars, and blue sky are hidden. NWS official observations make these measurements.When talking about “Partly Sunny” and “Partly Cloudy” in future or forecast terms, the definitions can be even more specific.  Instead of the sky description for “right now,” the forecast looks ahead.  To describe how long sky conditions will remain a certain way, certain definitions are used.  Partly Sunny means only part (less than half) of the time period will be sunny. In that same respect, Partly Cloudy means only part of the period will be cloudy. From least cloud cover to most cloud cover when talking about the future sky conditions, the scale is: sunny, mostly sunny, partly cloudy, partly sunny, mostly cloudy, cloudy. Mostly sunny means more sun than clouds, partly sunny means more clouds than sun, and partly cloudy generally means an equal amount of clouds and sun.Because of their “close call” definitions, “Partly Cloudy and Partly Sunny are essentially the same thing,” said David Wert, meteorologist-in-chief at the National Weather Service Office (Blacksburg.) “Both are used for conditions when the average amount of opaque cloud cover ranges from 45 percent to 75 percent. We usually use ‘partly sunny’ for daytime conditions, and ‘partly cloudy’ for nighttime conditions under these situations. It wouldn’t make too much sense to use ‘partly sunny’ for a nighttime condition.”Amy Freeze at Addison Elementary

Amy Freeze at Addison Elementary

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