The extratropical transition of Typhoon Merbok

September 16th, 2022 |
Airmass RGB imagery from Himawari-8, 1800 UTC 10 September – 2100 UTC 16 September 2022

Typhoon Merbok became a very strong extratropical storm as it moved through the Bering Sea on 15 – 16 September. The animation above shows the development (in the eastern third of the domain) of the tropical cyclone and, starting later in the day on 14 September, its subsequent interaction and merger with a mid-latitude system that moves out over the Pacific Ocean from Asia. The deep red/orange region in the Himawari-8 airmass RGB is associated with strong descent in association with an intrusion of stratospheric air with higher potential vorticity. The potential vorticity structure of this system is discussed in more detail by Prof. Jon Martin (UW Department of Atmospheric and Oceanic Sciences) here at that Department’s weekly Weather Watch (starting at 44 minutes).

Himawari-8 data in this animation is courtesy JMA. Note in the animation the persistence of Typhoon Nanmadol. That typhoon has generated significant swell and the National Weather Service in Guam issued High Surf Advisories from Guam to Saipan. Also, the daily appearance of Keep-Out Zones (see a previous blog post on this subject; here is a NESDIS/OSPO site on the topic) is apparent on the western and eastern limbs of the globe.

Back in 2014, Typhoon Nuri also evolved into a very strong Bering Sea extratropical cyclone — albeit much later in the year! (Link)

ProbSevere LightningCast Probabilities for Guam

September 15th, 2022 |
RealEarth display of Himawari-8 Band 13 (10.4 µm) infrared imagery and LightningCast Probability contours, 1320 – 1420 UTC on 15 September 2022 (Click to enlarge)

At the request of the National Weather Service forecast office in Guam (where the National Weather Service’s day begins), CIMSS is computing a small region of LightningCast Probabilities that uses Himawari-8 data. The Guam forecast office issues a lightning ‘advisory’ if lightning is possible or occurring within 20 mi of the Guam Airport, and a lightning ‘warning’ if lightning is possible/occurring within 5 mi of the airport. LightningCast probabilities will help in this task. Forecasters will be evaluating its performance in the coming weeks.

LightningCast imagery is available in a RealEarth instance here (at that website, there is a small drop-down menu titled ‘Select Sector’; Choose Guam). An example animation is shown above. (Guam is located at the outer fringes of Typhoon Nanmadol in the image) In contrast to the scenes under GOES-East’s and GOES-West’s view, GLM data are not available. In the forecast office, ground-based lightning sources are available. This animation (from John Cintineo, CIMSS) shows LightningCast probabilities with Earth Networks Total Lightning. Animations online, as shown above, show only Himawari-8 data and LightningCast probability contours.

As with GOES-R LightningCast computations, Himawari-8 uses Visible (0.64 µm), near-infrared (1.61 µm) and infrared (10.41 µm and 12.3 µm) observations. Resolution differences at 1.61 µm (1 km for GOES-R and 2 km for Himawari-8) and slight differences in infrared spectral responses, especially for band 13 (centered near 10.33 µm for GOES-R and 10.41 µm for Himawari-8) may have an as-yet unknown impact on LightningCast probabilities.

LIS observations over Typhoon Hinnamnor

September 1st, 2022 |
Himawari-8 Band 13 Infrared imagery (10.41 um) and LIS Flash Events, 1539-1542 UTC on 1 September 2022

The International Space Station carries a variety of instruments, including the Lightning Imaging Sensor (LIS), designed to extend the Lightning Climatology from the Tropical Rainfall Measuring Mission (TRMM). ISS overflew Typhoon Hinnamnor at about 1540 UTC on 1 September (image, from this site). The lightning animation above (click here for an animated gif) shows data from 1539 UTC until 1543 UTC, with >80 flash events occurring.  The observed lightning is far from the ragged eye of the storm.

The Joint Typhoon Warning Center (link) and the Japan Meteorological Agency (link) have more information on this typhoon.  Previous blog posts on Hinnamnor are here and here.  Himawari-8 data are courtesy JMA.


Super Typhoon Hinnamnor once again reaches Category 5 intensity

August 31st, 2022 |

JMA Himawari-8 Visible (0.64 µm) images [click to play animated GIF | MP4]

2.5-minute rapid scan JMA Himawari-8 Visible (0.64 µm) images (above) showed rapidly-intensifying Typhoon Hinnamnor as it once again reached Category 5 intensity (ADT | AiDT | SATCON) about 3 hours after local sunrise on 31 August 2022. Mesovortices rotating within the eye were evident though breaks in patchy high clouds overhead.

2.5-minute Himawari-8 Infrared (10.4 µm) images (below) revealed convection within the eyewall region which exhibited cloud-top infrared brightness temperatures of -80°C and colder (violet pixels).

JMA Himawari-8 Infrared (10.4 µm) images [click to play animated GIF | MP4]

Several hours before sunrise, a toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 1749 UTC, viewed using RealEarth (below) revealed concentric mesospheric airglow waves in the DNB image, propagating away from Hinnamnor (primarily to the north of the storm).

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, valid at 1749 UTC [click to enlarge]

The mesospheric airglow waves were less evident in an earlier comparison of Suomi-NPP VIIRS Day/Night Band and Infrared Window images, valid at 1700 UTC (below) — however, at that time the DNB displayed bright streaks near the eye, indicative of clouds illuminated intense lightning activity.

Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, valid at 1700 UTC [click to enlarge]