Heavy rainfall over the Hawaiian island of Kauai

April 15th, 2018 |

GOES-15 Water Vapor (6.5 µm, left) and Infrared Window (10.7 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Water Vapor (6.5 µm, left) and Infrared Window (10.7 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

A series of back-building thunderstorms produced very heavy rainfall and flash flooding (Public Information Statement | Local Storm Reports | CoCoRaHS) over the northern and eastern portion of Kauai on 14-15 April 2018. GOES-15 (GOES-West) Water Vapor (6.5 µm) and Infrared Window (10.7 µm) images (above) showed these deep convective storms, which exhibited cloud-top infrared brightness temperatures in the -60 to -70 ºC range (red to black enhancement).

Even though the JMA Himawari-8 AHI instrument provides more frequent Water Vapor and Infrared Window images (every 10 minutes, compared to every 15-30 minutes with GOES-15) at a higher spatial resolution (2-km at satellite sub-point, vs 4-km with GOES-15),  Hawai’i is located near the limb of the Himawari-8 view — so parallax was playing a major role in the apparent location of the important convective features. Note how the primary thunderstorms were displayed to the east of Kauai on the Himawari-8 images, in contrast to directly over the island on GOES-15 images.

Himawari-8 Water Vapor (6.9 µm, left) and Infrared Window (10.4 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

Himawari-8 Water Vapor (6.9 µm, left) and Infrared Window (10.4 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The MIMIC Total Precipitable Water product (above) showed that high amounts of tropical moisture were drawn northward across Hawai’i by the circulation of an upper-level trough — depicted by mid/upper-level atmospheric motion vectors — that was situated west/northwest of the islands (below).

GOES-15 Water Vapor (6.5 µm) images with mid/upper level atmospheric motion vectors [click to play animation]

GOES-15 Water Vapor (6.5 µm) images with mid/upper-level atmospheric motion vectors [click to play animation]

Super Typhoon Jelawat

March 30th, 2018 |

Himawari-8 “Red” Visible (0.64 µm) Imagery, hourly from 2200 UTC 29 March through 0800 UTC 30 March (Click to animate)

Super Typhoon Jelawat has developed in the central Pacific Ocean, to the west of Guam and the Marianas Islands. The hourly imagery, above, from Himawari-8, from 2200 UTC on 29 March through 0800 UTC on 30 March show a rapid eye development. Satellite presentation seems best at around 0500 UTC, with a well-defined eye. Subsequently, high clouds covered the eye as it became less symmetric.

Himarwari-8 AHI Band 13 (“Clean Window”, 10.41 µm) Infrared Imagery, 2300 UTC on 29 March 2018 through 0140 UTC on 30 March 2018 (Click to enlarge)

Infrared Imagery (10.41 µm) imagery, above, shows a well-defined eye shortly after 0000 UTC. Following a data outage, imagery from 1400 UTC to 1600 UTC, below, shows a central region of cold convective clouds, but no obvious eye.

Himarwari-8 AHI Band 13 (“Clean Window”, 10.41 µm) Infrared Imagery, 1420 UTC on 30 March 2018 through 1600 UTC on 30 March 2018 (Click to enlarge)

Water Vapor Infrared Imagery from Himawari, below, shows that outflow from Jelawat is well-established to the north; outflow appears to be entrained into the mid-latitude westerlies. MIMIC Total Precipitable Water for the 24 hours ending 1600 UTC on 30 March (shown underneath the water vapor infrared imagery below) also shows the entrainment of tropical moisture around Jelawat into mid-latitudes.  The Total Precipitable Water shows a band of rich moisture extending to the east-southeast of Jelawat, portending a wet period for the Marianas Islands.

Himawari-8 AHI Water Vapor Imagery, Bands 8 (6.24 µm) and 10 (7.35 µm) at 1600 UTC on 30 March 2018 (Click to enlarge)

Morphed Microwave Observations of Total Precipitable Water, 1700 UTC on 29 March 2018 to 1600 UTC on 30 March 2018 (Click to enlarge)

Morphed Storm-centered Microwave Imagery for the 24 hours ending at 0900 UTC on 30 March, 2018 (from this site), show the rapid intensification after 0000 UTC on 30 March.  (Update:  a similar animation that ends at 1900 UTC on 30 March 2018 demonstrates a rapid collapse of the eyewall convection!)

Morphed Microwave Imagery for the 24 hours ending at ~0900 UTC on 30 March 2018 (Click to enlarge)

Full-resolution Visible Imagery from AHI (Band 3, 0.64) is shown below. (Faster and slower animations are available). A rapid organization and clearing of the eye is apparent around 0400 UTC with an equally-rapid apparent subsequent obscuration.

Full-Resolution Himawari-8 “Red” Visible (0.64 µm) Imagery, hourly from 0000 UTC 30 March through 0850 UTC 30 March (Click to animate)

GCOM overflew the storm at around 1610 UTC on 30 March, and the toggle below shows the 36.5 and 89.0 Ghz imagery over the storm (the same enhancement is used in each image).  The 36.5 Ghz imagery suggests a very asymmetric storm.  Eyewall convection in the 89 Ghz imagery is not robust. (These data were downloaded at the Direct Broadcast antenna on Guam and are courtesy Kathy Strabala, SSEC/CIMSS)

GCOM AMSR-2 36.5 and 89.0 GHz imagery over Jelawat, 1604 UTC on 30 March 2018 (Click to enlarge)

NOAA-20 and Suomi NPP also both overflew Jelawat around 1600 UTC on 30 March. The toggles below show NOAA-20 and then Suomi NPP Day Night Band visible imagery. and Infrared 11.45 Imagery, at 1549 and 1639 UTC. (Imagery courtesy William Straka, SSEC/CIMSS)  In contrast to the Visible and Infrared imagery from Himawari earlier in the day (at top), an eye is not present.  (Note that NOAA-20 data are provisional, non-operational, and undergoing testing still.)

VIIRS Infrared Imagery (11.45 µm) from NOAA-20 (1549 UTC) and Suomi NPP (1639 UTC) on 30 March 2018 (Click to enlarge)

VIIRS Day Night Band Visible Imagery (0.70 µm) from NOAA-20 (1549 UTC) and Suomi NPP (1639 UTC) on 30 March 2018 (Click to enlarge)

Suomi NPP also overflew the storm on 29 March 2018, at 0421 UTC. This was before Jelawat’s rapid intensification. The toggle below again uses data from the Direct Broadcast antenna on Guam and shows VIIRS visible (0.64 µm) and infrared (11.45 µm) imagery, MIRS products (Total Precipitable Water and Rain Rate) derived from data from the ATMS microwave sounder on Suomi NPP, and individual microwave channels from ATMS: 31, 88, 165 and 183 Ghz.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) Imagery, MIRS Total Precipitable Water and Rain Rate, and individual Suomi NPP ATMS Channels: 31, 88, 165 and 183 GHz, all at 0421 UTC on 29 March 2018 (Click to enlarge)

Interests in the Marianas Islands should closely monitor the progress and evolution of this storm. This site and this site both have information on the system.

Cyclone Marcus west of Australia and south of Java

March 22nd, 2018 |

Himawari-8 AHI Band 13 (10.4 µm) infrared imagery, 0900-1540 UTC on 22 March 2018 (Click to animate)

NOAA-20 Imagery shown in this post is Non-Operational and preliminary and undergoing testing.

Himawari-8 captured the slow southward progress of Cyclone Marcus along 105 E Longitude between 0900 and 1540 UTC, as shown above.  During those six hours, the storm presentation suggested weakening, with a reduction in the central dense overcast and a warming of the eye.

Earlier, on 21 March at around 1800 UTC, the storm was at Category 5 Intensity on the Saffir-Simpson scale, and showed excellent presentation in the Day Night Band imagery, despite the lack of lunar illumination, and in the infrared (Click here for a toggle between the 0.70 µm Day Night Band Visible imagery and the 11.45 µm infrared imagery from Suomi NPP).  Significant Mesospheric Gravity Waves are apparent in all three images, the first (1710 UTC 21 March) and last (1850 UTC 21 March) from NOAA-20, and the middle (1800 UTC 21 March) from Suomi NPP.  (The waves are most prominent in the 1710 UTC Image from NOAA-20) The figure shows how Suomi NPP and NOAA-20 data can be used to create animations. A similar animation with Infrared Imagery (1710, 1800, and 1850 UTC) is below. (Suomi NPP and NOAA-20 Imagery courtesy Will Straka, CIMSS).

VIIRS Day Night Band Visible (0.70 µm) Imagery at 1710 UTC (from NOAA-20), 1800 UTC (from Suomi NPP), and from 1850 UTC (from NOAA-20) (Click to enlarge)

VIIRS Day Infrared (11.45 µm) Imagery at 1710 UTC (from NOAA-20), 1800 UTC (from Suomi NPP), and from 1850 UTC (from NOAA-20) (Click to enlarge)

Morphed microwave imagery for the 48 hours ending at about 1300 UTC on 22 March (from this site) show the evolution of the strong convection surrounding Marcus.  Eyewall convection has diminished on 22 March.

Morphed Microwave imagery centered on Cyclone Marcus for the 48 hours ending 1300 UTC on 22 March 2018 (Click to enlarge)

Added: Suomi NPP and NOAA-20 also observe the atmosphere at Microwave wavelengths using ATMS (The Advanced Technology Microwave Sounder). This toggle (created using McIDAS-V and data from the NOAA CLASS system) shows the 31 and 88 Ghz observations with the 11.45 VIIRS observations of the eye of Marcus at 1757 UTC on 21 March. The same brightness temperature enhancement is used for each image. Note that each observation shows a slightly different center location for the storm.

Transitory Solar Reflectance in GOES-R Series Imagery

March 5th, 2018 |

GOES-16 Visible (0.64 µm) animation, 1637-1732 UTC on 5 March 2018 (Click to enlarge)

Animations of GOES-16 Visible, near-Infrared and shortwave Infrared over North America shortly before the Vernal Equinox, and shortly after the Autumnal Equinox, (that is, when the Sun is overhead in the Southern Hemisphere) show bright spots that propagate quickly from west to east (these features were first noted by Frank Alsheimer of the National Weather Service). The animation above shows the visible imagery (0.64 µm) over the Continental United States on 5 March 2018 (Click here for a slower animation speed). Brightening over regions between 30 and 40 N between 1637 UTC and 1732 UTC is apparent. The animation below of the shortwave infrared (3.9 µm) shows slight warming (Click here for a slower animation), as might be expected with reflected solar energy. The brightening is also apparent in the Band 4 “Cirrus”  (1.37 µm) — in fact, a closer look at southern Colorado reveals the bright signature of sunlight reflecting off solar panels at the Alamosa Solar Generating Facility (Google maps).

GOES-16 Shortwave Infrared (3.9 µm) animation, 1637-1732 UTC on 5 March 2018 (Click to enlarge)

The increased reflectance can cause the ABI Clear Sky Mask to mis-characterize clear regions as cloudy (See the animation below; click here for a slower animation). Thus, Cloud properties (Cloud-top Height, Temperature, Pressure, etc.) can be identified in clear regions.

GOES-16 Clear Sky Mask (White: Clouds ; Black : No Clouds) from 1637 UTC – 1732 UTC on 5 March 2018 (Click to enlarge)

The bright spots in the visible, and warms spots in the shortwave infrared, occur when the Earth’s surface, the GOES Satellite and the Sun are aligned on one line. If you were within the bright spot with a powerful telescope trained on the Sun, you would see the GOES Satellite transecting the solar disk. The location of these bright spots changes with season: they appear in the Northern Hemisphere shortly before the (Northern Hemisphere) vernal equinox and shortly after the (Northern Hemisphere) autumnal equinox. Similarly, they appear in the Southern Hemisphere shortly before the (Southern Hemisphere) vernal equinox and shortly after the (Southern Hemisphere) autumnal equinox. On the Equinox, the bright spots are centered on the Equator.

This animation (courtesy Daniel Lindsey, NOAA/CIRA and Steve Miller, CIRA) shows where the reflection disk moves during the days around the Northern Hemisphere Autumnal Equinox; a similar animation for the Northern Hemisphere vernal equinox would show a disk starting at the North Pole and moving southward with time.

The animation below (from this link that is used for calibration exercises), shows the difference in reflectance (Bands 1-6) or Brightness Temperature (Bands 7-16) between 1657 and 1652 UTC on 3 and 5 March 2018. Two things are apparent: The centroid of the largest difference in solar reflectance has moved southward in those two days, as expected; the effect of this solar backscatter is most obvious in the visible, near-infrared and shortwave infrared channels (that is, bands 1-7 on the ABI).  The effect is most pronounced in clear skies.

Time Difference in each of the 16 ABI Channels (1657 – 1652 UTC) on 3 and on 5 March 2018 (Click to enlarge)

This reflectance feature is also detectable in legacy GOES Imagery. However, the great improvements in detection and calibration in the GOES-R Series ABI (and AHI on Himawari-8 and Himawari-9) and the better temporal resolution with the GOES-R Series allows for better visualization of the effect.

The feature also shows up in “True Color” Imagery, shown below (from this site). Geocolor imagery (shown here), from CIRA, also shows the brightening.

CIMSS Natural True Color Animation ending 1757 UTC on 5 March 2018 (Click to enlarge)

Thanks to Daniel Lindsey and Tim Schmit, NOAA/ASPB, Steve Miller, CIRA and Mat Gunshor, CIMSS, for contributions to this blog post.