Federated States of Micronesia

Chuuk State:  Rainfall was abundant throughout Chuuk State during the 1st Quarter of 2011, with some large month-to-month and island-to-island variations. There was a north-south gradient of rainfall across Chuuk State, with islands located further south (e.g., the southern Mortlocks) receiving the most rainfall (upwards of 40 inches) during the 3-month period, and islands further to the north (e.g., Fananu) receiving the least (just over 25 inches). During March, some locations (e.g., Nama and Ta) received over 20 inches of rain. At this time of year, 20 inches of rain in one month is unusual. In the time series of rainfall at Chuuk WSO extending from 1956 to 2007, there were only two occurrences of 20 inches or more of monthly rainfall during any January, February or March. In addition, there were only 12 occurrences of monthly rainfall over 15 inches, or 7.5% of all 1st Quarter months in the period 1956 to 2007. At its latitude, most of the islands of Chuuk State have a short dry season, with the average monthly rainfall during February and March falling below 10 inches. During the years that follow El Niño, the short dry season in Chuuk State is prolonged and much drier. During times of waning La Niña (the current scenario), or during the onset of El Niño, it tends to be wet throughout Chuuk State.

Chuuk State Rainfall Summary 1st Quarter 2011

Climate Outlook: Conditions at Chuuk State are anticipated to continue to be wetter than normal. This is supported by long-range computer forecasts, and the known typical behavior of the weather and climate of Chuuk State when La Niña wanes during the spring and becomes ENSO-neutral by the summer.

For the next five months (April 2011 through August 2011), there is a low risk chance (1-in-15, or 7%) of a tropical storm within the boundaries of Chuuk State. It is more likely that the depression stages of developing tropical cyclones will form in Chuuk State (bringing abundant rain), and then pass to the northwest before becoming numbered or named cyclones. Later in the year (September through December), the risk of a tropical storm or typhoon occurring within the boundaries of Chuuk State will be higher (possibly 10-15%). In any case, these named cyclones, or their precursors, will bring at least one or two episodes of heavy rain and gusty westerly winds across Chuuk State from September through December.

Predictions for Chuuk State from April 2011 through March 2012 are as follows:

Forecast rainfall quantities represent BEST ESTIMATES given the probabalistic forecast for each particular season and station.

source: UOG-WERI