How to reconcile hourly vs. daily probability of precipitation in the forecast?

Asked by: Chelsea Perry

How is precipitation forecast calculated?

occurring at any one spot in the area covered by the forecast. One simple equation used among meteorologists is P = C x A, or the probability of precipitation equals the meteorologist’s confidence that it will rain, times the percentage of the area that is expected to get rainfall.

How do you interpret precipitation probabilities?

If a forecast for a given county says that there is a 40% chance of rain this afternoon, then there is a 40% chance of rain at any point in the county from noon to 6 p.m. local time.

How accurate is weather forecast hourly?

The Short Answer:



A seven-day forecast can accurately predict the weather about 80 percent of the time and a five-day forecast can accurately predict the weather approximately 90 percent of the time. However, a 10-day—or longer—forecast is only right about half the time.

How is probability used in weather forecasting?

A probability forecast includes a numerical expression of uncertainty about the quantity or event being forecast. Ideally, all elements (temperature, wind, precipitation, etc.) of a weather forecast would include information that accurately quantifies the inherent uncertainty.

How is precipitation percentage calculated?

Confidence multiplied by the percentage of the area forecasted equals the “percentage of precipitation.” So if there’s a 100% confidence that 30% of the area will see rain, then it’s a 30% chance [(1 x 0.3)100 = PoPs].

How is weather forecast calculated?

The official formula from the National Oceanic and Atmospheric Administration is: PoP = C x A, where C is the confidence percentage and A is the percentage of the area with precipitation. Put your percentages into this official formula. Multiply your confidence times the area estimate.

What does 80% chance of rain mean?

An “80% chance of rain” means that there is an 80% chance that rain will fall somewhere within the forecasted area. Rain refers to 0.01 inch or more.

What does percentage of rain mean in forecast?

The rain percentage on your weather app refers to the chance you will experience a measurable amount of precipitation (0.01”) in the given period. Meteorologists determine the Probability of Precipitation by multiplying their forecasting confidence in rain occurring with the expected areal coverage of rain.

What does 60% chance rain mean?

If they say 60% chance of rain, 60% of their area will experience rain at some point during the forecast period. The forecaster will often mention which interpretation they adhere to. Keep in mind, PoP only refers to the chance of precipitation, NOT how much rain you will get.

What is the most accurate weather forecast?

AccuWeather gathers the best and most comprehensive weather data to deliver forecasts with Superior Accuracy. Forecasts are pinpointed for every location on Earth and extend further ahead than any other source.

Which weather model is most accurate?

Types of Weather Models



The ECMWF is generally considered the most accurate, just slightly so, than the American system. However, they do provide access to weather predictions worldwide. The most accurate model, on average, is the European model.

What factors would make it difficult to make an accurate weather prediction?

Well, their ability to predict the weather is limited by three factors: the amount of available data; the time available to analyze it; and. the complexity of weather events.

What does 30% precipitation mean?

This is called the “probability of precipitation” and is sometimes abbreviated as POP. It is expressed in a percentage. So, if there’s a 30% chance of rain, what does that mean? It means where you are, the odds of you seeing rain is 30%.

What does a 20% chance of rain mean?

A forecast of a 20 percent chance of rain means the forecaster believes there is a one in five chance (20 percent) that measurable rain will occur in the time period covered by the forecast.

What does 30% chance of rain mean on weather app?

(NEXSTAR) – You turn on the local news in the morning or open your phone’s weather app and you see there’s a 30% chance of rain in the forecast. You (quite reasonably) take that to mean there’s a 30% probability it will rain where you live and a 70% probability it won’t rain.

What does 80% chance of rain mean?

An “80% chance of rain” means that there is an 80% chance that rain will fall somewhere within the forecasted area. Rain refers to 0.01 inch or more.

What does 60% chance rain mean?

If they say 60% chance of rain, 60% of their area will experience rain at some point during the forecast period. The forecaster will often mention which interpretation they adhere to. Keep in mind, PoP only refers to the chance of precipitation, NOT how much rain you will get.

What does a 30% chance of rain mean?

It is expressed in a percentage. So, if there’s a 30% chance of rain, what does that mean? It means where you are, the odds of you seeing rain is 30%. Think of it as if someone were to say, “my schedule is busy, so there’s only about a 30% chance I might make it to the baseball game.”

Does 40% chance of rain mean it will rain?

Instead, it means a certain percentage of the forecasted area will definitely see rain—so if you see a 40% chance, it means 40% of the forecasted area will see rainfall.

What does 50% chance of rain actually mean?

A 50 percent chance of rain means there is a 50 percent chance for any one spot in the forecast area to get wet during the forecast period.

What does a 20% chance of rain mean?

A forecast of a 20 percent chance of rain means the forecaster believes there is a one in five chance (20 percent) that measurable rain will occur in the time period covered by the forecast.