The Direct Broadcast Processing System (DBPS) at SSEC/CIMSS now has a website (http://erb-dbps.ssec.wisc.edu/browser/MADISON/) that serves up VIIRS imagery and products that become available very quickly. As I type this at 2011 UTC, for example, NOAA-21 data from the 1937 UTC overpass is available. The animation below shows 3 different true-color scenes (produced with polar2grid) over the midwestern United States. The greening of Spring has reached into southern Illinois, but snow-cover is still widespread over the Upper Peninsula of Michigan and much of Canada. Lakes in Minnesota still have ice cover, but those in Wisconsin are clear of ice.

Imagery from a variety of VIIRS channels, including the Day Night Band, are routinely produced. Satellites providing imagery also include Metop-B and Metop-C, NOAA-18 and NOAA-19, GCOM-W1 and Aqua. Microwave imagery is available, at 36.5 and 89 GHz (both horizontal and vertical polarities) as shown in the toggle below. In addition, level 2 products from MIRS can be accessed (Total Precipitable Water, Rain Rate, and microwave brightness temperatures at 31, 89, 157, 165, 183 and 191 GHz!)

Perhaps you noticed the clear skies over the Great Lakes above and asked yourself: “I fancy a swim; I wonder what the Lake Surface Temperatures are?” AWIPS-ready tiles produced at CIMSS (by polar2grid) and displayed in AWIPS, below, show the answer. Lake Superior and most of Lake Huron have surface temperatures in the mid-30s (^oF); Lake Michigan is a bit warmer, closer to 40^oF, except along the far southern shore, where waters are just a bit warmer. Only western Lake Erie is uniformly “warm” with temperatures in the upper-40s to around 50. Enjoy your swim there. Lake Surface Temperatures are not yet at the DBPS site, but their implementation is planned.

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VIIRS imagery is also available at the eosdb url: https://ftp.ssec.wisc.edu/pub/eosdb/; the latency at that site is not as quick as at the DBPS site because the DBPS site incorporates only data from the Direct Broadcast antenna at CIMSS, whereas the eosdb site incorporates data from other Direct Broadcast sites, and it waits (typically up to 30 minutes) until those data are present before processing. Imagery at the eosdb site covers larger regions at the expense of latency. The NOAA-20 true-color imagery below, for example, includes information over South America that did not originate from the Madison downlink. This image of NOAA-20 orbits over North American on 16 April (source) includes a (very large) circle from which the CIMSS Direct Broadcast antenna can acquire data, but you’ll note it does not extend into South America.

DBPS websites are available for other Direct Broadcast antennas as well, as noted in this blog post.

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Target Sector (2.5-minute interval) JMA Himawari-9 AHI Red Visible (0.64 µm) and Clean Infrared Window (10.4 µm) images (above) showed Cyclone Errol as it was rapidly intensifying off the northern coast of Western Australia on 15-16 April 2025. About 2 hours after the end of the above animation, Errol peaked at 140 kts — Category 5 intensity — at 1200 UTC (SATCON). Errol exhibited a pinhole eye during the time period shown — a feature frequently observed with rapidly-intensifying tropical cyclones. Cloud-top infrared brightness temperatures in the eyewall region of Errol were in the -80s C (shades of violet to purple).

A NOAA-20 VIIRS Day/Night Band image valid at 0503 UTC (below) provided a higher-resolution view of the 10-mile diameter pinhole eye.

A Sentinel-1A Synthetic Aperture Radar (SAR) image (source) at 1610 UTC (below) sensed a maximum radial wind velocity of 124.8 knots in the northeast quadrant of Errol.

Factors favoring Errol’s rapid intensification included very warm water that the storm was traversing, and an environment of low deep-layer wind shear (below). Sea Surface Temperature and Wind Shear images were sourced from the CIMSS Tropical Cyclones site.

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Instrument issues at the weather station in Pago Pago (related to Hydrogen generation) means that balloon launches occur only once every other day, at 0000 UTC on odd days. The sounding for 15 April/0000 UTC (1 PM Samoa Standard time on 14 April) is shown below.

Two different JPSS satellites overflew the Samoan Islands just after 0000 UTC on 15 April 2025, and two profiles were created just west of Tutuila, as shown below.

The toggle below compares the two NUCAPS soundings shown in the image above to the 0000 UTC rawinsonde from Pago Pago. There is, overall, agreement, although (of course), the NUCAPS soundings are very much smoother.

At 1200 UTC, no rawinsonde was launched. But NUCAPS profiles were available at around 1200 and 1300 UTC as shown in the animations below.

If you compare the 0000 UTC NUCAPS profiles to those sensed around 1200-1300 UTC, what changes do you see, and how might those changes have been sensed by a rawinsonde if it had been launched. The later profiles all show dryer conditions at mid-latitudes (precipitable water values have dropped by about 0.4″). Temperatures above 700 mb are very similar in the two profiles, but the later profile is a bit cooler between the surface and 850 mb

The information change in the 12h between NUCAPS profiles (note also that there was a NUCAPS profile at around 0900 UTC!) can help you decide what a full-resolution sounding (made by a radiosonde) might have looked like.

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Thursday 17 April is the 125th anniversary of the beginning of American Sovereignty over American Samoa. Part of the celebration includes the Fautasi, a regatta that depends on weather. What tools are available to help forecast in the long-term and in the short-term? The animation above (from the CSPP Geosphere site) shows the Night Microphysics RGB during the early morning of 14 April, and periodic convection is occurring. The low clouds — white and pink against the blue background — are occasionally spawning deeper convection that is a deep red in the RGB. These convective towers are short-lived. This kind of information might be useful in the short-term for diagnosing where precipitation is occurring the night before the regatta.

MIMIC Total Precipitable Water fields, above, show the Samoan Islands along the southern edge of deeper moisture that is the South Pacific Convergence Zone between the islands and the Equator. Animations such as these can help a forecaster anticipate the approach (or retreat) of deep moisture that could support heavy rains.

The GOES-18 Clear-Air estimates of Total Precipitable Water, below, similarly show a gradient just south of the Samoan Islands, with values dropping from over 2″ over American Samoa (the purple enhancement) to about 1.5″ to the south (the yellow enhancement).

The green points above show where Legacy Profiles exist, and the animation below highlights the profile very close to Pago Pago in the center of Tutuila. The low-level stability in the sounding and mid-level dry air are consistent with the occasional convective development (and quick dissipation) observed in the Night Microphysics imagery above.

LightningCast probabilities (available at this site) can be used in the short term for Decision Support for outdoor activities. The animation below shows probability fields for the overnight hours, 1200-1500 UTC on 14 April 2025, matching the animations above. Probabilities with these showers to not become large, and GLM lightning observations are not present.

GREMLIN fields (1000-1500 UTC) that estimate radar returns are shown below (from here). Hit-or-miss showers are diagnosed.

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What can be used for winds and waves? Two PacIOOS buoys exist around American Samoa, and both are producing data. The plots below show that higher waves 7-7.5 feet, are at the Auunu buoy to the east. Waves are closer to 6 feet at King Poloa. At both locations, waves are approaching from the southeast, and the King Poloa site is somewhat in the lee of Tutuila. Altimetric wave heights are also available (link) — but at present the observations at that website are not up to date.

Scatterometry data gives sea-surface winds; strong winds near the Samoan Islands might build higher waves. Those data are available here, but as with the wave heights at that site, they are not up to date today. Scatterometry data are available at this osisaf website, however. ASCAT winds from MetopC (over the Samoan Islands) and from MetopB (to the east, i.e., upstream of the Samoan Islands) show values between 15 and 20 knots.

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Update, 15 April 2025: Today I noticed a feature (at the CSPP Geosphere site) in the Night Microphysics RGB that was moving over American Samoa, i.e., that hazy lighter blue, highlighted here. What does this feature in the RGB represent?

To answer that, I first loaded up the Band 7 (shortwave IR, 3.9 µm) infrared imagery, and one noteworthy feature is the lack of cloud development in/around that feature. This suggests the RGB image is detecting a region of dry air; it might show up in the RGB because the Split Window Difference — that highlights moisture differences in the atmosphere — is part of the Night Microphysics RGB.

The inset Split Window Difference field (source) has a darker smudge signifying dryer air in the same region as the lighter region in the RGB.

Of course, there are GOES-18 level 2 products that can help reveal the answer. The Total Precipitable Water field overlain on top of the Band 7 imagery, below, shows a distinct dry patch (TPW of less than 1.25″!) right where the feature in the RGB appears.

MIMIC Total Precipitable Water fields at about the same time (1400 UTC/15 April) show the dry patch as well.

For more information on the weather around Pago Pago, refer to the National Weather Service website and/or the Facebook page of the Pago Pago office.

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