One of the products demonstrated at this year’s HWT is synthetic water vapor transmittance (WVT) imagery. The product, a ratio of 0.91 μm to 0.86 μm reflectances, is based on the existence of water vapor absorption at 0.91 μm. Dividing by 0.86 μm helps to highlight the water vapor signature. As NOAA does not yet operate a satellite channel at 0.91 μm, synthetic imagery is created for HWT from the High-Resolution Rapid Refresh model run through the Community Radiative Transfer Model. However, EUMETSAT’s latest geostationary satellite, Meteosat-12, does contain 0.91 μm and 0.86 μm channels on its Flexible Combined Imager (FCI), and is used to augment the synthetic imagery during HWT.
Figure 1 shows an FCI WVT loop over northeastern Africa and the Arabian Peninsula from 12 May 2026. The darker regions are indicative of higher amounts of total precipitable water (TPW). Noteworthy regions of higher TPW can be seen along the west and south coasts of Saudi Arabia and Yemen as moisture moves onshore from the Red Sea and the Gulf of Aden. The greater moisture along and equatorward of the Sahel is also very apparent. The high spatial and temporal resolution afforded by the satellite imagery allows for very accurate monitoring of water vapor during the day in clear regions.
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