A strength of the Night Microphysics RGB in the tropics is that it’s pretty easy to use it in regions of mostly clear skies to diagnose wind shear, because high clouds will show up as dark red, and low cloud show up as pale pink or cyan (see this annotated image). In the animation above (from the CSPP Geosphere site), low clouds around and to the west of the Samoan Islands are moving towards the west-northwest. High clouds are moving in the same direction: Wind shear values are low. In contrast, in the northeastern part of the domain above, low clouds are (also) moving towards the west-northwest — but high clouds are moving off to the east: Wind shear values are high.

A wind shear analysis from 1200 UTC, below, taken from the SSEC/CIMSS Tropical Weather website (direct link to shear plot) confirms what the Night Microphysics RGB suggests.

View only this post Read Less

Northern California enjoyed a clear day on 23 January, and the animation above, from the CSPP Geosphere site, (click here for a direct — but not permanent — link to the animation) shows the shadow of Mount Shasta (see the still image below identifying both the mountain and the shadow) shortening over the course of the morning. Note that clouds are also present around the mountain peak as well, although this webcam screen capture from 2100 UTC (source) shows only clear skies. Also of interest in the animation above: the sloshing of the low clouds within the valleys of southern Oregon.

Click here and here for similar blog posts on the shadow of Denali. Thanks to Mike Stavish, SOO at WFO MFR for drawing our attention to this event.

View only this post Read Less

Monthly means of full disk GOES-17 brightness temperatures¹ for Bands 8, 10, and 13 have been computed from 2019 to 2021, totaling 36 months. This is an expansion of similar work that had been done for Band 13 for a single year. Band 8, centered on 6.2 µn, is sensitive to upper-level water vapor. While Band 10, centered on 7.3 µn, is sensitive to low-level water vapor. Band 13 is the clean longwave infrared window channel and observes at 10.3 µn.

Brightness temperature can be thought of as the amount energy (radiance) being reflected or emitted from Earth and measured by satellite sensors. These fields of averaged brightness temperature are useful for assisting forecasters in knowing what can be expected from satellite retrievals on monthly timescales, especially in remote Pacific regions where forecasters are heavily reliant on satellite data.

While a large amount of smoothing is expected for a monthly average, the resulting full disk fields are not homogenous. Certain patterns appear. The ITCZ is noticeable. Also, an area of warmer brightness temperature is visible west of Hawaii during winter months in the animations for Bands 8 and 10. This is likely associated with a synoptic high pressure for that region.

Reference to a Climatic Atlas created by Sadler et al. (1987) from the School of Ocean and Earth Science and Technology confirms potential for a synoptic high pressure region that is usual for that time of year. However, because the Sadler fields are derived surface measurements (temperature, pressure, wind, and stress), comparing them to GOES-17 ABI brightness temperatures is not exactly an “apples to apples” situation.

¹ Brightness temperatures are computed from radiances.

View only this post Read Less

The Community Software Processing Package (CSPP) includes Flood Detection algorithms that can be applied to VIIRS data at Direct Broadcast sites (such as at CIMSS). The daytime NOAA-20 orbit over California on 22 January 2023 overflew mostly clear skies, resulting in the True Color and False Color imagery shown above, and the diagnosed regions of floods, mainly in the Sacramento and San Joaquin River basins. Note that flooding in these two river basins can also be a result of agricultural diversions to support rice farming. So a good question is: Was the water put there intentionally — or did it flood? The modest flood signal in the Salinas River basin (south and east of Salinas) is more likely actual flooding.

These images were created using geotiff images from CSPP that were inserted into Google Earth and are courtesy Kathy Strabala, SSEC/CIMSS. VIIRS flood imagery (including imagery displayed in concert with ABI and AHI data) are also available here.

View only this post Read Less