An Examination and Verification of Forecasts Containing "Heavy Rain" Issued by WFO Gray, Maine: 2014–19

Each year during the warm season, WFO Gray, ME issues many forecasts containing the phrase “heavy rain,” or similar phrasings. However, the inclusion of “heavy rain” is left to the forecasters’ discretion and may not accurately reflect the conditions across the entire forecast area. In addition, there is no specific definition used by the National Weather Service to characterize “heavy rain.” In order to identify such “heavy rain forecast days”, a database for 5 warm seasons (May 1 – September 30) from 2014 – 2019 was developed to examine the usage of “heavy rain” and phrases similar (i.e. “torrential rain”) in both the Hazardous Weather Outlooks and in the Zone Forecasts for the Gray, ME County Warning Area (CWA). This database is then used to verify the occurrence of such events for these days using a working definition of “heavy rain” that will be developed from a combination of literature review and analysis of local precipitation trends. Preliminary results show that “heavy rain forecast days” are most common in July, with a third of all such days occurring in that month. August has the next highest amount of “heavy rain forecast days” with roughly a quarter of all occurrences. This trend is present in both the analysis of the Hazardous Weather Outlooks and in the Zone Forecasts.