Where the weather comes from and how fresh it is
4Search does not make its own forecasts. Weather brings together information from public weather services and shows each piece with its source and its age. This article lists where each part of a Weather page comes from and how to tell how fresh it is.
#Which source gives what
| What you see | Where it comes from |
|---|---|
| Forecasts, current conditions and alerts in the United States | The National Weather Service (NOAA) |
| The forecasters' discussion | The local National Weather Service office |
| Radar | NOAA's radar mosaic of the country's weather radars |
| Satellite pictures | NASA's imagery service and NOAA's GOES satellites |
| The base map on the radar | The U.S. Geological Survey's National Map |
| Air quality | AirNow, from the U.S. Environmental Protection Agency and its partners |
| Hurricanes and tropical outlooks | The National Hurricane Center |
| Normals, records and the monthly calendar | NOAA's regional climate centers |
| Forecasts outside the U.S., days 8 to 10 for U.S. places, and the UV index | MET Norway |
| Current conditions outside the U.S. | Airport reports, through NOAA's Aviation Weather Center |
| Place names | GeoNames |
| Weather news | The 4Search news index: what the press published |
The same list is in the notice at the bottom of every Weather page.
The notice at the bottom of every Weather page, with the sources and a reminder that data can lag.
#How fresh it is
Weather copies data from these sources on a schedule, so a page can be a little behind them. Most figures say how old they are:
- Current conditions: "Observed at" a station, and how many minutes ago.
- The forecast: "National Weather Service forecast updated" some hours ago, or "MET Norway forecast updated" for places elsewhere.
- Radar: a new picture about every two minutes. If the pictures are more than 25 minutes old, the map says so.
- Air quality: the reporting area, and how long ago it reported.
- Hurricanes: "Updated", how long ago the storm's figures were issued.
- The forecasters' discussion: when it was issued.
- Alerts: when each one was issued and by which office.
#Forecasts are not all alike
- For U.S. places, the first seven days are the National Weather Service's forecast, written and reviewed by forecasters. Days 8 to 10 are MET Norway's outlook, a computer model with no forecaster's review, and are tagged Extended outlook.
- Places outside the United States use MET Norway's forecast throughout, and their hourly detail covers about two and a half days.
- Climate figures for recent days are preliminary and can be corrected later.
#Common questions
Does 4Search change the forecasts?
No. Forecasts, alerts and readings are shown as the sources give them. Weather converts units and writes the forecast in words for places outside the U.S. from MET Norway's figures.
Why does Weather's forecast differ from another weather site's?
Other sites may use different sources or their own forecasts, and update at different times. Weather shows the National Weather Service's forecast for U.S. places.
Why is a reading an hour old?
Stations report at intervals, often hourly. The note under the current conditions says how old the reading is.