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.

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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.

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The University of Wisconsin-Madison Space Science and Engineering Center owns and operates a network of low-earth orbiting direct broadcast satellite antennas around the United States, and provides software support for partner institutions with similar antenna systems. Last week, a new version of the web interface hosted by each antenna’s on-site direct broadcast processing system was rolled out to improve the experience of browsing the wide array of satellite imagery and derived products available. Products displayed are automatically generated utilizing a collection of CSPP (Community Satellite Processing Package) software, including Polar2Grid, for designated fixed sectors and tropical cyclones within view of satellite overpasses from a given antenna, with a typical latency of 5 – 15 minutes after an overpass ends.

The new browser pages are available at the following locations:

• Honolulu, HI (located at Honolulu Community College): http://soest-hcc1.hcc.hawaii.edu/browser/
• Miami, FL (located at the NOAA Atlantic Oceanographic and Meteorological Laboratory): https://dbps.aoml.noaa.gov/browser
• Mayagüez, PR (located at the University of Puerto Rico at Mayagüez): http://dbps.ece.uprm.edu/browser/
• Hampton, VA (owned by Hampton University): http://dbps.cas.hamptonu.edu/browser/

National Weather Service Pacific Region users also have internal access to similar product browser sites featuring data from SSEC’s antenna located at NWS Guam and NOAA’s antenna at the Inouye Regional Center on Ford Island, Hawaii. These pages are lightweight and perform well on desktop and mobile browsers.

To use the page, you’ll first have to select a location to view. Each site has at least one static sector centered over the antenna location, and if there are tropical storms in the region, additional locations will be listed on this first screen:

After selecting a location, you can now select which products you’d like to view on the left sidebar. Currently, a selection of Level 1 visible and infrared imagery from VIIRS, MODIS, and AVHRR, plus Level 1 microwave imagery from AMSR-2 is shown in the browser, along with Level 2 microwave products from MiRS (ATMS and AMSU/MHS). The full list is broken down first by level, then product name. By default, similar products from multiple satellite constellations are grouped together, and when possible, similar product nicknames to those used for GOES ABI are used. For example, clicking the down arrow next to True Color (red circle below) reveals that the EOS and JPSS constellations provide this product, and clicking the down arrow next to JPSS (green circle below) reveals that True Color products are available from S-NPP, NOAA-20, and NOAA-21. By default, all will be toggled on when the True Color product is loaded, but you can click any of the names to remove them from the listing if you wish.

Selecting products will open a thumbnail listing on the right side of the page with the selected images from the last week in reverse chronological order. When you click on a specific product thumbnail, it will go full screen. If you wish to download the image that you are currently viewing, there is a download button in the upper right. Also on this screen, you can use the keyboard’s arrow keys or the on-screen arrows to go backwards and forwards in time through the products that you selected. This allows you to make an impromptu animation or image toggle of your choosing, as shown below:

Future plans include rolling out a version of this site to a dedicated test processing server located on the campus of the University of Wisconsin-Madison, including additional products of interest, and making it easier to know when upcoming satellite overpasses are expected. And finally, a big thanks to SSEC software developer Geoff Yoerger for his efforts creating this new image browser functionality!

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The dominant story in the continental United States on February 18 is the significant winter weather that is impacting nearly every state east of the Rocky Mountains. A glance at this morning’s National Weather Service alert map shows a continuous band of cold weather warnings from the Canadian border down to central Texas, with a fierce winter storm stretching from Kansas to the Atlantic Ocean. NWS forecasters are reporting that they are camping out in their offices in order to ensure continuity of coverage so that the public they serve can remain safe and aware of these dangerous conditions.

Overnight lows in the upper midwest were particularly cold, with temperatures below -30 F in parts of the Dakotas (the coldest minimum temperature was -45 F at Antelope Creek ND). These extremely cold temperatures are often associated with notable temperature inversions above the surface. As surface temperatures cool overnight, the strong infrared emissivity of snow enhances the radiative cooling. However, as air is a poor conductor of heat, temperatures aloft remain relatively unaffected. This is particularly clear in the 1200 UTC balloon launched from Bismarck, North Dakota. Note how the surface temperature (-36.3 C) is barely warmer than the temperature at 500 mb (-37.7 C). The sounding also notes that the lifting condensation level (LCL) of around 890 mb is substantially warmer than the surface.

When cloud temperatures are the same or warmer than surface temperatures, it can be challenging to interpret infrared satellite imagery. For example, here is the GOES-16 ABI Band 13 image from 1150 UTC as displayed using the enhanced infrared color scale.

Looking at the northern shore of Michigan’s upper peninsula and the western shore of the lower peninsula, it appears that the banded structures of lake effect snows are present in the shades of blues. Therefore it is reasonable to assume that a lake effect event is ongoing in that region of the image, but given that the temperatures of the clouds are basically the same as the underlying surface, it’s not obvious. But discerning what is happening in the Dakotas and Minnesota is far more difficult. Are there large stratiform clouds present, or are the surface temperatures so cold that they have cloud-like temperatures? This is where products like the night microphysics RGB can be very useful.

Normally, the noisy orange regions seen in the upper midwest and northern great plains indicate high, thick, very cold clouds. The speckles appear when brightness temperatures are less than -30 C due to noise in the 3.9 micron channel at extreme cold temperatures. However, there are clues in here that we’re actually looking at clear skies in those orange regions. Let’s zoom in on northern Minnesota.

Here, it is clear that the lakes, most notably Upper and Lower Red Lake in the center of the image, are differently colored than the surrounding regions. The greener tinge is a result of reduced influence of the 12.4-10.4 micron difference and enhanced influence of the 10.4-3.9 micron difference. This likely is surface ice which means this region is clear. Therefore, the orange regions in the RGB product indicate that skies are basically clear in Minnesota and North Dakota, with some cloud coverage in southern and western South Dakota showing up as darker reds. The lake effect snows are much more clearly visible as yellow in the RGB compared to the IR image where they are basically the same temperature as the surface. Since the RBG recipe uses the 3.9 micron channel as an ingredient, this product shouldn’t be used for interpretation much after 1200 UTC this time of year as the sun is about to rise and solar reflectance at 3.9 will dominate over emission.

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