Region
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Are the next 3 months likely to be unusually wet or dry?

This map shows the likelihood that total 3-month precipitation will be unusually high or low.

What do I do next?

If you see a colour over your region, possible responses include:

See the "More Information" tab for details on the forecast.

Explanation

Colors over the map correspond to how confident we can be in the forecast that the total amount of rainfall over the three-month forecast period will be either below normal (i.e., unusually dry, indicated by shades of orange and brown) or above normal (i.e., unusually wet, indicated by shades of blue) for the given area and time of year. Below-normal and above-normal rainfall typically each occur about once every three years (i.e., with a probability of 33%), and so shaded areas indicate increased risks of an unusually wet or dry season. Areas with higher confidence levels have darker shades (see color bar above).

This forecast shows only the likelihood of 3-month accumulated rainfall (or snow) being unusually high or low, and does not indicate chances of individual heavy rainfall events. The forecasts apply over large areas only, and should not be used to forecast local conditions, or as a flood forecast.

How to use this interactive map

Switch to another map: Select the dropdown menu at the top of the page, to the right of the blue “Forecasts” heading.

Return to the menu page: Click the blue link called “Forecasts” at the top left corner of the page.

Zoom in to a region:
Method 1: Pick a region from the list:

  1. Select the dropdown menu at the top of the page, titled “Region”
  2. Click on the region of interest, and the map will automatically refresh.

Method 2: Click-and-drag:

  1. Click the left mouse button at the upper-left corner of the region to which you would like to zoom.
  2. While holding down the button, drag the mouse to the lower-right corner of the region to which you would like to zoom.
  3. Release the left mouse button. The map will redraw automatically.

Zoom out to the global map:

  1. Move your mouse over the map, until you see three icons appear in the upper left corner.
  2. Click the icon of the magnifying glass.
  3. The map will redraw automatically. Note that the map cannot display areas outside of the latitudes initially shown on the interface (about 66.25S – 76.25N).

Change the date of the forecast: Forecasts are labeled by the month they were issued. You can find this label by moving your mouse over the map until you see a text box appear at the top with the date inside.

  1. To step forward or back by one month, click the corresponding buttons to the left or right of the text box, and the map will automatically refresh.
  2. To manually change the forecast issue date, type your date of interest into the text box. This must follow the format: “Jan 2008”. Then, press “enter” or click the “refresh” icon in the top left corner of the map.
  3. To produce an animation of these maps over a series of dates, type the date range into the text box. This must follow the format: “start date” followed by “to” followed by “end date”. For example “Jan 2008 to Dec 2008”.

Change the lead time of the forecast: Every month, a seasonal forecast is issued for the next three months; for example, in January, a forecast is issued for February-April (the default), which has a “lead time” of 1 month. A forecast issued in January for March-May has a lead time of 2 months, and April-June has a lead time of 3 months, because April is 3 months later than January.

  1. To change the lead time, move your mouse over the map until you see a text box appear with the date inside.
  2. To step forward or back by one month lead time, click the corresponding buttons to the left or right of the text box, and the map will automatically refresh.
  3. To manually change the lead time, type a number from 1 to 4 into the text box. Then, press “enter” or click the “refresh” (insert pic here) icon in the top left corner of the map.

Dataset Documentation

IRI Seasonal Precipitation Forecast
Data Dominant tercile probabilities for seasonal (3-month) precipitation for the four overlapping lead times from the IRI Net Assessment Forecast, issued every month at 2.5° lat/lon resolution
Data Source International Research Institute for Climate and Society, Net Assessment Forecasts, Map Room Forecast page, Data Library entry

Help

Contact help@iri.columbia.edu with any technical questions or problems with this Map Room, for example, the forecasts not displaying or updating properly.