WINDS

sample windrose

All meteorologists, but especially Air Quality Meteorologists, are interested in wind direction information at a given location. One tool that meteorologists use to provide a visual depiction of wind direction frequency at a given location is called a windrose because it displays wind information and sometimes it looks like a rose. It is most common to display windroses using the direction the wind came from. Most often windroses are displayed from 16 directions. However, to reduce bias created within windrose creation software, ME DEP Meteorologists are now using 36 direction windroses. As always each spoke provides information about wind speed as well. All windroses presented on subsequent pages provide this level of detail. If you are not familiar with windroses please go to our windrose how to page.

Within the field of Air Quality Meteorology it is accepted that during the course of 5 years most weather events expected to occur at a location will have occurred. So a data set of 5 consecutive years of wind speed and direction will display the general trend of winds at that site. Even though the windrose at one site may be created from a different 5 year span than another, each site's windrose should be a good representation of overall winds and can be compared to each other to learn how winds differ from one location to another.

It is important to note that surface topography and geography influence winds. Windroses from valley sites will show that the valley walls channel the wind. So, in a section of valley that runs north-south one will see that the north and south directions are fairly frequent. Windroses in a north-south valley will not be representative of an east-west valley nor of a nearby plain. Sites which are located near the coast often display sea and land breezes.

Therefore, windroses are ‘site specific' and should not be used to depict winds in a different location unless great care has been taken to review the two sites and all factors effecting winds are roughly equal. Likewise a windrose should not be used for a larger area or region unless the whole region is affected by the same topography and geography as the specific site. It is advisable to consult a meteorologist before deciding whether or not a windrose from one location would be an accurate representation of winds at another location.

Maine DEP maintains a number of monitoring stations around the state collecting air pollution data and some also collect meteorological data (DEP MET), mainly wind direction and speed. At DEP MET sites, wind data is collected continuously and a minute average is tabulated. An hourly average is calculated from that hour's 60 one minute averages*. This hourly data can be viewed in near-real time at Air Quality Monitoring. On a regular basis this data is checked for quality (QA) and archived.

In addition, during the 1980's and 1990's, there were a number of locations around the state where various industries were required to collect quality meteorological data using the same procedure as described above for the DEP. Since operating meteorological towers to such exacting standards is quite costly, once a location had 5 years of good high quality data that site was allowed to be shutdown. QA'd data from both DEP and industry sites was prepared for input into software which creates the windroses displayed on subsequent pages.

Since windroses from a number of locations are provided on these pages, one can find how winds vary across the state. Click on the site name listed below to view windroses for that site. Each site's web page will also give a brief description of the site, a map and the windrose.

Maine map

Each monitoring site listed below has a web page with a little information about the site, a map of the area and a windrose. These pages are slow to open because the images are large so you can view the details.

Links to sites:

Windrose speeds are in knots. 1 knot = 1.2 mph = 0.5 meters/second.

* IMPORTANT NOTE ABOUT WIND DATA COLLECTION METHODS: The way the National Weather Service (NWS) reports winds is different from the way DEP reports winds. Wind direction information on NWS sites is a ‘snapshot' of a moment in time rather than an hourly average. You can view the NWS current winds by following these steps:

Go to either Gray NWS or Caribou NWS depending on which part of the state concerns you.
Click on the map for the location you are interested in.
The resulting page displays the forecast for that location. On the right, part-way down the page, you will see the most current hour of weather data from the nearest NWS monitor to that location
Links to view data from other nearby NWS monitors or a 3 day history of hourly weather from that monitor are displayed under the current weather data.

meterology

WINDS