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Advected Layered Precipitable Water

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The Advected Layered Precipitable Water (ALPW) product generates an hourly, four-layer blended precipitable water map derived from five polar-orbiting satellites: Metop-B, Metop-C, SNPP, NOAA-20 (N20), and NOAA-21 (N21). Designed for atmospheric monitoring and weather analysis, the product features a 16 km spatial resolution mapped onto a global Cylindrical Equidistant (CE) projection, with measurements reported in millimeters (mm).

ALPW Global

Hourly Imagery by Pressure Layer

05/27/2026 All times UTC
Hour 300-500 mb 500-700 mb 700-850 mb Surface-850 mb
Loading ALPW image data�

Global animation frame preview

ALPW animation frame for 300-500 mb layer 300-500 mb
ALPW animation frame for 500-700 mb layer 500-700 mb
ALPW animation frame for 700-850 mb layer 700-850 mb
ALPW animation frame for surface-850 mb layer Surface-850 mb

About Advected Layered Precipitable Water

ALPW isolates water vapor content across four distinct atmospheric pressure layers: surface to 850 mb, 850 mb to 700 mb, 700 mb to 500 mb and 500 mb to 300 mb. Delivered hourly in NetCDF4 format fully compatible with AWIPS-2 systems, the dataset is structured as global floating-point arrays spanning 1,251 rows by 2,501 columns in a Cylindrical Equidistant (CE) projection. Layer precipitable water (LPW) values are derived from Microwave Integrated Retrieval System (MiRS) soundings and can be visualized in either millimeters (mm) or inches based on operational forecasting preferences.