High pressure and mild temperatures over the western Atlantic and adjacent Gulf waters early on 26 February 2025 (here is the 1200 UTC surface analysis) meant NOAA-20 VIIRS data could provide near-complete views of sea- (and lake-) surface temperatures. The above image was captured from the RealEarth website. The warm waters (mid-70s ^oF) of the Gulf Stream off the North Carolina coast are in very close proximity to cold (mid-40s ^oF). Direct Broadcast data processed into AWIPS-ready VIIRS tiles are available from CIMSS and an example swath is shown below.

A zoomed-in view over the Outer Banks of North Carolina, below, shows the strength of the SST gradient, from very warm to much colder in less than 40 miles.

The SSTs over the northern part of the South Atlantic bight, shown below, include filaments of colder water extending from the shelf waters out into the open ocean.

NOAA-20 True-Color imagery, below, from the VIIRS Today website, shows filaments of turbid water that suggest a link between the observed cold filaments above and cold fresher water from the Continent. (Note also the smoke plumes over the southeastern US!)

View only this post Read Less

5-minute CONUS Sector GOES-16 (GOES-East) Visible and Infrared images (above) displayed a thunderstorm that was moving southeast from Aberdeen (KABR) to Watertown (KATY) in northeastern South Dakota on 24 February 2025. While overall GLM-detected lightning activity was relatively modest, periodic increases in Flash Extent Density (orange to red pixels) were evident.

A Special Weather Statement was issued for this thunderstorm at 2058 UTC (below), advising on its potential to produce 50 mph winds and nickel-size hail. Note the slight northwest displacement of the Flash Extent Density pixels, compared to the thunderstorm overshooting top as seen in GOES-16 Visible and Infrared imagery — this is because the commonly-used Gridded GLM products (such as Flash Extent Density, Minimum Flash Area and Total Optical Energy) are not corrected for parallax. With this particular low-topped storm, the magnitude of GOES-16 parallax correction would be about 15 km (9 miles) to the southeast.

GOES-19 (Preliminary/Non-operational) Visible and Infrared images (below) included a red “T” denoting the location of a brief tornado that occurred at 2211 UTC, southeast of Watertown (NWS Aberdeen | SPC Storm Reports).

_________

LightningCast probabilities (source), below, from 2042 – 2232 UTC, showed high probabilities confined to the storm that produced the tornado; those probabilities diminished quickly after the tornado occurred.

View only this post Read Less

Hazardous weather conditions associated with winter storms and flooding can be seen throughout the northwestern continental United States due to the presence of an atmospheric river brining significant amounts of moisture from the eastern Pacific to the North American shore. Alerts include winter storm warnings in western Washington and flood warnings, watches, and advisories in northern Idaho and western Montana. Flood conditions are already primed by temperatures exceeding freezing in this part of the United States thus ensuring that meltwater is significant and surfaces are saturated.

Atmospheric rivers are long, narrow bands of enhanced moisture transport. Depending on their strength, they can provide positive impacts like bringing desperately needed rain to regions of drought or fire. However, they can also have negative impacts by creating flooding, mudslides, and other hazardous conditions. Satellites, of course, are an excellent tool for diagnosing the position and strength of atmospheric rivers. The water vapor imagery from geostationary satellites provides a simple way to identify where the rivers are and how quickly they are flowing. In this example from AWIPS, the 6.19 micron brightness temperature shows a band of enhanced water vapor content streaming in from the Pacific toward the west coast of the continental US. It’s even possible to see the river helping to feed the development of an offshore extratropical cyclone that is approaching the Oregon coast.

The river is even more easily seen in the Morphed Infrared Microwave Imagery at CIMSS (MIMIC) total precipitable water (TPW) product. Since microwave sounders are currently only present aboard polar-orbiting platforms, derived products often contain gaps between overpasses. MIMIC takes the snapshot view of a TPW swath and uses numerical weather prediction winds to move the observed field in space so that it can be matched to and blended with adjacent TPW swaths. This creates a near-seamless view of the global TPW field at an hourly temporal resolution. In this case, MIMIC clearly identifies the position of the river and its origin from the warm, moist air near Hawaii. Real time imagery from MIMIC is available here.

As noted above, the impact of all this moisture as it hits shore can be significant. One impact is local streamflow rates. The following image shows the past month of stream observations from the Palouse River near the Idaho/Washington border. The river swelled to nearly triple its depth in the last 48 hours, and has reached a level that is by far the greatest it has experienced in the last year. Numerous similar examples can be seen on the USGS streamflow gauge site.

View only this post Read Less

10-minute Full Disk scan True Color RGB images from GOES-18 (GOES-West), GOES-17, GOES-19 (Preliminary/Non-operational) and GOES-16 (GOES-East) created using Geo2Grid (above) showed the slow drift of nearshore ice and the more rapid motion of lake effect clouds across southern Lake Michigan on 18th February 2025.

The respective satellite locations over the Equator at that time were: GOES-18 (137.0 W longitude), GOES-17 (104.4 W longitude), GOES-19 (89.5 W longitude) and GOES-16 (75.2 W longitude). GOES-17 had been temporarily brought out of storage and was drifting slowly from 12th-15th February 2025, approximately 0.3 degrees of longitude in total. All GOES-17 ABI imagery during this “Longitude Test” were resampled to the nominal 105 W location (the final GOES-17 image during this test period was at 1540 UTC on 18th February). GOES-17 products were analyzed for any potential impacts that this shift in longitude might cause. The overall goal of the Longitude Test was to determine what product impacts (if any) there might be when GOES-16 (currently operational as GOES-East) is moved to 75.5 W in March 2025, ahead of GOES-19’s arrival (GOES-19 is then scheduled to become operational as GOES-East on 4th April). This also tested our ability to track a GOES-R series satellite as it moved (and still receive quality data).

GOES-16 Visible images (below) included plots of surface wind/temperature/weather. Winds were generally light, and early morning temperatures across southeast Wisconsin and northeast Illinois were around -10 F away from the lake and around -5 F along the lakeshore. Air temperatures were much warmer beneath the lake effect clouds that were moving inland across northern Indiana and western Michigan (with some sites reporting light snow).

A GOES-16 Visible image with plots of Metop ASCAT winds (below) depicted speeds of 15-25 knots over Lake Michigan at 1508 UTC.

View only this post Read Less