HALL REPORT: Precipitable water – a forecasting variable

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ALEXANDRIA, La. (KALB) - Weather Forecasters and Meteorologists look at a lot of variables when putting together their daily forecasts. One of these variables is the precipitable water value.

This variable indicates the amount of moisture that is above a certain point. To make it clear here, it does NOT indicate how much it will rain, but rather, how much moisture is in the air.

Here’s an example: if you have a 1-inch precipitable water value, this value does not indicate it will rain 1 inch. It indicates that the overall moisture above a certain location is condensed would be 1 inch.

The Gulf of Mexico is a significant weather player across Louisiana as moisture gets transported in significant amounts, leading to increased values of overall precipitable water. This value gives a forecaster an idea of the amount of moisture that is in the air. Higher values of precipitable water show greater availability of moisture to make rainfall if precipitation develops in your area or region. Increased values of precipitable water occur in air that has a higher average dewpoint through the depth of the troposphere. (Louisiana for example).

Here’s a general guide for interpreting the precipitable water values:
Values of 0.50 inches or less mean very low moisture content, 0.50 to 1.25 inches means low moisture content, 1.25 to 1.75 inches means moderate moisture content, 1.75 to 2 inches means high moisture content, 2 inches or higher means very high moisture content.

To sum up, this variable does NOT indicate how much it will rain but rather how much moisture is in the air at a certain location.

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