Tropical Disturbances in both Hemispheres

February 19th, 2019 |

Morphed Total Precipitable Water for the 24 hours ending 0100 UTC on 19 February 2019 (Click to enlarge)

Morphed Total Precipitable Water imagery (from this site) for the 24 hours ending at 0100 UTC on 19 February 2019, above, shows two Tropical disturbances spinning on either side of the Equator. Cyclone Oma in the Southern Hemisphere was northwest of New Caledonia in the Coral Sea. A second disturbance over the north Pacific, albeit very close to the Equator, was near Pohnpei and will pass near Chuuk later this week. Interests in Micronesia should pay attention to this area of disturbed weather.

Himawari-8 Clean Window imagery (10.41 µm) (courtesy JMA), below, shows the better organization of Oma in contrast to the more disorganized nature of the tropical wave over Pohnpei.

Himawari-8 AHI Clean Window (10.41 µm) Infrared Imagery, 1400 UTC 18 February – 0230 UTC 19 February 2019 (Click to play animated gif)

Refer to the CIMSS Tropical Webpage (Link) for more information on Oma. The National Weather Service on Guam is issuing statements on the tropical system in Micronesia. (From 0245 UTC on 19 February 2019, for example) (Update: This is now Tropical Depression 02W; a projected path as of 1200 UTC on 19 February is here. The current forecast has this storm achieving typhoon status late Wednesday).

First GEOKOMPSAT-2A imagery (in stereo view with Himawari-8)

February 4th, 2019 |

Himawari-8 (left) and GEO-KOMPSAT-2A (right) Full Disk Imagery, 0310 UTC on 26 January 2019 (Click to enlarge)

The Korean Meteorological Administration (KMA) has released its first true-color image created with data from the AMI sensor on the GEOKOMPSAT-2A (GK2A) satellite that was launched in late 2018.   This first image from GK2A is experimental and preliminary, just like the initial images from Himawari-8,  -9, GOES-16 and GOES-17 were preliminary:  all newly-launched satellites go through a check-out period during which radiometric and geometric calibration work is ongoing.  That is what is happening with the  GK2A satellite now.  Despite the preliminary nature of the GK2A imagery, however, it can be paired with Himawari-8 imagery to create stereoscopic views of the Earth — in true color!   To view the image pair in three dimensions, cross your eyes until three circles appear, and focus on the circle in the middle;  it should appear then as a sphere.

(Image pair courtesy Bodo Zeschke, Australian Bureau of Meteorology ;  Himawari image courtesy JMA ; GK2A image courtesy KMA and Dr. Hyesook Park. GEOKOMPSAT-2A is also known as Chollian-2a)

PyroCumulonimbus cloud in Australia

January 25th, 2019 |


Himawari-8 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.7 µm, middle) and Infrared Window (10.3 µm, bottom) images [click to play to animation | MP4]

JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.3 µm) images (above) showed the development of a pyroCumulonimbus (pyroCb) cloud from a bushfire that was burning in the eucalypt forests of eastern Victoria, Australia on 25 January 2019. A rapid-scan “Target” sector was positioned over the region beginning at 0522 UTC, providing images every 2.5 minutes (instead of the routine 10-minute interval). Cloud-top infrared brightness temperatures became colder than -40ºC (the threshold for pyroCb classification) after 0230 UTC, and eventually cooled to around -55ºC (orange enhancement). This temperature roughly corresponded to an altitude around 12 km, according to nearby Melbourne rawinsonde data (plot | text).

A closer view of Himawari-8 “Red” Visible (0.64 µm) and Shortwave Infrared (3.7 µm) images (below) revealed the rapid southeastward run of the fire, as shown by the growth of the “hot spot” (black to red pixels) on Shortwave Infrared images. The darker gray appearance of the pyroCb cloud is due to the presence of smaller ice crystals at the cloud top — these smaller ice crystals are more efficient reflectors of incoming solar radiation, making the cloud tops appear warmer than those of conventional cumulonimbus. Vigorous updrafts driven by the intense heat of the fire limit the in-cloud residence time for ice crystal growth, which leads to smaller particles being ejected at the pyroCb cloud top.

Himawari-8 "Red" Visible (0.64 µm, left) and Shortwave Infrared (3.7 µm, right) images [click to play to animation | MP4]

Himawari-8 “Red” Visible (0.64 µm, left) and Shortwave Infrared (3.7 µm, right) images [click to play to animation | MP4]

In a comparison of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP (at 0311 UTC) and NOAA-20 (at 0501 UTC) images viewed using RealEarth (below), cloud-top infrared brightness temperatures were in the -55 to -58ºC range (darker shades of orange).

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP (0311 UTC) and NOAA-20 (0501 UTC) images [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP (0311 UTC) and NOAA-20 (0501 UTC) images [click to enlarge]

Stereoscopic views of a small storm over the North Pacific Ocean

January 16th, 2019 |

Himawari-8 AHI and GOES-17 ABI Band 13 (10.41 µm and 10.35 µm, respectively) at 0400 UTC on 16 January 2019 (Click to enlarge)

GOES-17 Data in this post are preliminary and non-operational.

The toggle above shows clean window imagery from the Advanced Himawari Imager (Band 13, 10.41 µm) on Himawari-8 (data courtesy JMA) and clean window imagery from the Advanced Baseline Imager (ABI, Band 13, 10.3 µm) on GOES-17 (GOES-17 data are non-operational). There is a small developing storm between the Hawai’ian Islands and Alaska that is resolved by both satellites.  The storm is in between the two satellites and therefore ideal for stereoscopic views created from Visible 0.64 µm imagery (Band 3 for AHI, Band 2 for GOES-17).  That is shown below.  Thirty-minute timesteps are used because GOES-17 scans a full disk every 15 minutes (in Mode 3 that is currently operational; Mode 6, if used, scans a Full Disk every 10 minutes; and Mode 4, continuous Full Disk, the highest data rate for the GOES-R series, scans a Full Disk every 5 minutes). Himawari scans a Full Disk every 10 minutes. The three-dimensional representation facilitates the identification of warm conveyor belts associated with this developing storm. (This link shows the same animation but with the imagery flipped so it can be viewed in Google Daydream).

GOES-17 non-operational Visible (0.64 µm) imagery (left) and Himawari-8 Visible (0.64 µm) imagery (right), every half-hour from 2000 UTC on 15 January to 0400 UTC on 16 January (Click to animate)

Thanks to Mary Ellen Craddock, Northrop-Grumman, for the reminder that stereo imagery is possible with GOES-17 and Himawari.  (It should be even better with Himawari-8 and South Korea’s GEOKOMPSAT-2A!)