Hurricane Force low off the US East Coast

April 2nd, 2019 |

GOES-16 "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a cluster of deep convection just to the north of the center of a rapidly-intensifying midlatitude cyclone (surface analyses) off the coast of North Carolina on 02 April 2019. In addition, convection was later seen developing along the north-south cloud band marking the leading edge of the cyclone’s cold front. The rapid deepening of this hurricane force low easily met the criteria of a bomb cyclone — its central pressure dropped 20 hPa in just 12 hours (from 1004 hPa at 18 UTC on 02 April to 984 hPa at 06 UTC on 03 April).

The primary convective cluster began to exhibit a large amount of lightning after 1830 UTC, as seen in plots of GOES-16 GLM Groups (below). To the east of this intensifying convection, one ship report at 18 UTC included winds from the east at 50 knots — in addition, a moderate to heavy shower of hail was being reported and their surface visibility was restricted to 1.25 miles (18 UTC surface analysis).

GOES-16 "Red" Visible (0.64 µm) images, with GLM Groups and surface wind gusts plotted in red [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with GLM Groups and surface wind gusts plotted in red [click to play animation | MP4

There were several factors pointing to the development of a sting jet with this storm, as discussed here and here. GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below) revealed distinct areas of warming/drying (darker shades of yellow to orange) that possibly highlighted rapidly-descending air associated with a sting jet (for example, on the 1946 UTC images).

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play animation | MP4]

After 23 UTC, GOES-16 “Clean” Infrared Window (10.3 µm) images (below) portrayed the formation of a large eye-like feature indicative of a warm seclusion (00 UTC surface analysis). Lightning activity remained very high during that time.

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play animation | MP4]


A comparison between 1-km resolution Terra MODIS Infrared Window (11.0 µm) imagery at 0237 UTC with an Aqua MODIS Sea Surface Temperature product at 1755 UTC on the following afternoon (below) showed that the storm intensified and formed the large eye-like feature over the northern portion of the axis of warmest Gulf Stream water (where SST values were in the 70-76ºF range).

Terra and Aqua MODIS Infrared Window (11.0 µm) images from 0237 UTC and 0649 UTC, along with the Aqua MODIS Sea Surface Temperature product at 1755 UTC [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image at 0237 UTC, along with the 1755 UTC Aqua MODIS Sea Surface Temperature product [click to enlarge]

With a nighttime overpass of the NOAA-20 satellite at 0651 UTC, the eye-like feature was apparent in VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below). Although the Moon was in the Waning Crescent phase (at only 8% of Full), that illumination with the aid of airglow was sufficient to provide a useful “visible image at night” using the Day/Night Band; a streak of bright pixels was due to intense lightning activity within a line of thunderstorms just ahead of the cold front. Note: the NOAA-20 images are incorrectly labeled as Suomi NPP.

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

NOAA-20 VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images, with an overlay of the 06 UTC surface analysis [click to enlarge]

Mode 6 is now the default scanning strategy of both GOES-16 and GOES-17

April 2nd, 2019 |

GOES-16 Cloud Top Temperature, 1345-1620 UTC on 2 April 2019 during Mode 3 Scanning (Click to enlarge). Mode 6 scanning with 10-minute full disk imagery started at 1600 UTC.

The most common scanning strategy for GOES-R satellites since GOES-16 became operational has been “Flex” Mode, Mode 3: During each 15 minutes, 1 full disk, 3 CONUS and 30 Mesoscale scans are achieved (Link showing Mode 3 Scanning. This YouTube Video shows Mode 3 Scanning with two adjacent mesoscale sectors). (Mode 4 — continuous 5-minute full disk imagery — has been implemented as well, as noted here).

In early 2014, before launch, researchers at NOAA’s Advanced Satellite Products Branch and CIMSS in Madison, Wisconsin suggested that some of the time where the ABI wasn’t scanning (The white space in this graphic) could be used to provide larger CONUS (or PACUS) scans. This didn’t happen, in part because it changed the dimensions of an ABI sector. However, in August 2014, an email exchange with the lead ABI instrument designer from Harris Corporation led to the concept of using the extra time instead to increase the cadence of full disk imaging from every 15 minutes to every 10 minutes in the “flex” mode. (Click to see a ‘Time-time’ chart of Mode 6 for GOES-16, and for GOES-17;  You might notice that GOES-16 and GOES-17 have slightly different Mode 6 scanning strategies.  Mode-6M for GOES-17 differs because of the timings of different calibration looks meant to mitigate errors associated with the faulty Loop Heat Pipe (link 1, link 2, link 3). Changes were need to in the ground system to support this new scan mode, and those changes are now operational.

The change to 10-minute full disk imagery matches the scanning of JMA’s AHI imager (and it will match the next generation EUMETSAT imager as well). It also gives the finer time resolution in the full disk domains for monitoring convection, fires, volcanic ash plumes, turbulence, etc., in regions outside CONUS and PACUS scans. In particular, Alaska region of the National Weather Service receives full-resolution Alaska sectors created from the full-disk imagery, and those sectors will now switch from a 15-minute cadence to a 10-minute cadence.  All of Central and South America will now also have imagery every 10 minutes!

This page at the goes-r.gov website has more information on scanning strategies. You can also find more information about scanning schedules and scan sectors here.

Many Baseline Products will also adopt the 10-minute cadence.  For example, compare the GOES-16 Baseline Cloud Top Temperature imagery above, from April 2, with Mode 6 scanning and 10-minute temporal resolution at the end of the animation, with the GOES-16 Baseline Cloud Top Temperature with Mode 3 and 15-minute temporal resolution below from April 1. (An animation with Mode 6 scanning at the end showing Band 13 “Clean Window” 10.3 µm imagery is here).

GOES-16 Cloud Top Temperature, 1400-1645 UTC on 1 April 2019 during Mode 3 Scanning (Click to enlarge)

Additional Full Disk animations covering a 6-hour period — 3 hours before/after the 1600 UTC Mode 6 activation time — are available from GOES-17 (Visible | Water Vapor) and GOES-16 (Visible | Water Vapor).