Mode 6 Testing with GOES-17

September 25th, 2018 |

GOES-17 11.2 µm (Infrared Window Channel) Full Disk Images, 0915 – 1510 UTC on 25 September. Note the cadence change at 1300 UTC: every 15 minutes before 1300 UTC, every ten minutes after (Click to animate)


GOES-17 imagery shown here is preliminary and non-operational.

The default scanning strategy for the Advanced Baseline Imager on GOES-16 is Mode 3, also known as Flex Mode.  In Mode 3, there are 2 Mesoscale Sectors scanned every minute, a CONUS sector scanned every 5 minutes, and a Full Disk image scanned every 15 minutes.  GOES-17 is undergoing Mode 6 scanning, starting today, and proceeding into early October.  In Mode 6, there will continue to be two Mesoscale sectors scanned every minute, and a CONUS sector scanned every 5 minutes.  However, Full Disk imagery will be scanned every 10 minutes, rather than every 15.  6 Full Disk images each hour would align GOES-17 (and GOES-16, when and if this becomes operational) with default Full Disk imagery scanning on Himawari.

The animation of Full-Disk imagery above, showing Band 14 (11.2 µm), the window channel, on GOES-17, shows that Mode 6 scanning — every 10 minutes — started at 1300 UTC on 25 September.  Prior to that time, Mode 3 scanning — every 15 minutes — was occurring. GOES-16 Scanning remains Mode 3.

Added: Simultaneous GOES-16/GOES-17 Mode 4 (Continuous Full Disk — the highest data rate from the ABI) testing is planned for 1 October 2018.

Alaska: a thunderstorm, single digits and a volcano

September 25th, 2018 |

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images (above) captured an unusually late thunderstorm that produced small hail at Anchorage PANC (surface observations) on 24 September 2018. The coldest cloud-top infrared brightness temperature was -53.8ºC, which was colder than the -46.3ºC tropopause temperature on the 00 UTC Anchorage sounding. This particular thunderstorm (Anchorage averages only 1-2 per year) even featured a wall cloud:



In far northeastern Alaska, snow cover across the North Slope and Brooks Range was evident in a sequence of Suomi NPP VIIRS Visible (0.64 µm) images (below). Since there were also areas of low cloud present (both north and south of the primary snow cover), the VIIRS Shortwave Infrared (3.74 µm) images could be used to discriminate between these low clouds — whose supercooled water droplets were effective reflectors of solar radiation, making then appear warmer or darker gray — and the cloud-free areas of snow cover.

Sequence of 4 Suomi NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]

Sequence of 4 Suomi NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]

The presence of this snow cover aided strong nighttime radiational cooling as a ridge of high pressure moved over the North Slope (surface analyses), and on the following morning temperatures dropped as low as 4ºF (the temperature later reached 3ºF at Toolik Lake):

Finally, along the Alaska Peninsula, Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images revealed the bright glow and hot thermal signature of the ongoing eruption of Mount Veniaminof at 1204 UTC and 1344 UTC (below).

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 1204 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 1204 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 1344 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 1344 UTC [click to enlarge]

Coincidentally, on this day GOES-17 began a test of Mode 6 operation which performs a Full Disk scan every 10 minutes. Although the Alaska Peninsula was on the extreme northwest limb of the Full Disk scan, Veniaminof’s thermal anomaly or “hot spot” (darker black pixels) could still be detected and monitored at 10 minute intervals using Shortwave Infrared (3.9 µm) imagery (below). However, an increase in layered cloud cover southeast of that area later in the day (in tandem with the extreme satellite view angle) eventually masked the warm thermal signature — a more direct view from overhead with Suomi NPP VIIRS still showed a very hot volcano summit (96.9ºC) at 2156 UTC.

GOES-17 Shortwave Infrared (3.74 µm) images [click to play animation | MP4]

GOES-17 Shortwave Infrared (3.74 µm) images [click to play animation | MP4]

Since there were no significant ash emissions from Mount Veniaminof on this day, no volcanic signature was evident on GOES-17 “Red” Visible (0.64 µm) imagery (below).

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

West Pacific Super Typhoon Trami

September 24th, 2018 |

Himawari-8 Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed Typhoon Trami at Category 4 intensity during the 23-24 September 2018 period. The typhoon was going through an eyewall replacement cycle during this time — as seen on the MIMIC-TC product — which halted the period of rapid intensification that began early on 23 September (ADT | SATCON). Note the significant trochoidal motion (wobble) of the storm during the first half of the animation.

With the arrival of daylight late on 24 September UTC (25 September local time), the satellite presentation of then Category 5 Trami was quite striking, with surface mesovorticies within the large eye seen on both Visible and Infrared rapid-scan (2.5-minute interval) images (below). The deep-layer mean steering flow was also very light, allowing the forward motion of Trami to slow considerably.

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.4 µm, right) images [click to play animation | MP4]

Trami was in an environment characterized by low values of deep-layer wind shear, as shown in an animation of Himawari-8 Infrared Window (10.4 µm) images from the CIMSS Tropical Ctclones site (below).

Himawari-8 Infrared Window (10.4 µm) images, with deep-layer wind shear analysis at 00 UTC [click to enlarge]

Himawari-8 Infrared Window (10.4 µm) images, with deep-layer wind shear analysis at 00 UTC [click to enlarge]

After nightfall on 25 September, and overpass of NOAA-20 provided VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images of Trami at 1634 UTC (below; courtesy of William Straka, CIMSS). Due to the very slow motion of the typhoon, strong winds had induced upwelling of cooler water from below the ocean surface — which in turn brought a gradual weakening of the storm to a Category 4 intensity. Ample illumination from a Full Moon demonstrated the “visible image at night” capability of the Day/Night Band.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]


Though the eye had become more cloud-filled, distinct surface mesovortices were still present — captured in stunning detail by an astronaut on the International Space Station:


Land breeze convergence cloud band in Lake Michigan

September 23rd, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface and buoy reports [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow cloud band that had developed in Lake Michigan in response to land breeze induced convergence on the morning of 23 September 2018. With inland temperatures cooling overnight into the 30s and 40s F (the coldest in both Wisconsin and Michigan was 29ªF) and lake water temperatures of 64ºF (at the North Michigan buoy 45002) to 69ºF (at the South Michigan buoy 45007), a well-defined nocturnal land breeze was established along the western and eastern shorelines of the lake.

Nighttime VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC (below) showed that the cloud band had not yet formed at those times.

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

The Terra and Aqua MODIS Sea Surface Temperature product (below) confirmed that mid-lake water temperatures were generally in the middle to upper 60s F (green to light yellow enhancement) across the entire length of Lake Michigan.

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

An examination of the MODIS SST product with overlays of RTMA surface winds (below) showed that there was no clear signature in the model wind field of enhanced convergence either before or after the mid-lake cloud band had formed.

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

However, an overpass of the Metop-A satellite at 1559 UTC provided ASCAT surface scatterometer winds that did a better job than the RTMA at highlighting the mid-lake convergence that was helping to sustain the cloud band (below). This example underscores the value that satellite-derived winds can have over even high resolution models.

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]