SAR winds near Tropical Storm Nepartak

July 27th, 2021 |
RCM1 SAR Winds over Tropical Storm Nepartak just east of Honshu, 0828 UTC on 27 July 2021 (Click to enlarge)

RADARSAT Constellation Mission One (RCM1) passed over Nepartak at 0828 UTC on 27 July 2021, and the image above shows the Synthetic Aperture Radar (SAR) winds derived at that time. There is a widespread region of ~40-knot winds (cyan to green in the color enhancement), a bit stronger than the 30-knot winds viewed by MetopA at 1040 UTC (shown here, in this blog post). How certain can a forecaster be of the even-stronger winds that exist in an area near the coast near 37.4ºN, 141.4ºE, and in an arc from 37.5ºN, 142.5ºE to 37.2ºN, 144ºE? There are isolated SAR estimates in that band that are near 60 knots! Are there other data sources to confirm that kind of wind? (See information at the bottom for clarification!)

The image below shows Himawari-8 Clean window imagery at 0829 UTC, just after the image above. Three points with cold cloud tops, suggestive of more vigorous convection, are indicated: (37.6ºN, 141.18ºE); (37.57ºN, 143.01ºE); (37.35ºN, 144.01ºE). The structures in the infrared imagery do match the structures in the SAR winds, but offset a bit to the north in the Himawari-8 imagery, as expected because of the parallax shift: features will be displaced away from the sub-satellite point, with the displacement increasing for higher clouds, and for greater distance from the sub-satellite point (on the Equator at 140.2ºE for Himawari-8). Convective downdrafts could be responsible for the highest winds shown in the SAR analysis.

Himawari-8 Clean Window Infrared (10.41 µm) imagery, 0829 UTC on 27 July 2021 (Click to enlarge)

The strong winds in the image are not observations of strong winds by SAR. Rather, these are most likely the result of reflection off of ice in the atmosphere — ice that is likely to be present around convective towers that have glaciated. (Thanks to Christopher Jackson, GST/NOAA, for this information!)

Tropical Storm Nepartak approaches Japan

July 26th, 2021 |
MIMIC microwave estimates of Total Precipitable Water, 1800 UTC on 26 July 2021 (Click to enlarge)

As the games of the 2021 Olympics progress, a weakening Tropical Storm Nepartak is moving over coastal waters to the east of Honshu, the main island of Japan. The Total Precipitable Water imagery, above, from MIMIC TPW, shows a plume of moisture wrapped around the circulation center. Himawari-8 Clean Window infrared (10.41 µm) imagery, below , from the Himawari-8 Target scene (courtesy of JMA; here’s a link to more JMA satellite imagery), shows the progression of the storm.

Himawari-8 Band 13 Clean Window Infrared (10.41 µm) imagery, 1712 – 2327 UTC, 26 July 2021 (Click to animate)

The forecast from the Joint Typhoon Warning Center (JTWC) as of 1800 UTC has the weakening storm backing into northern Honshu (forecast track; it’s also available from JMA). As of 2300 UTC, the center of Nepartak had moved north to Tokyo’s latitude, and convective bands on the west side of the storm are affecting areas around Tokyo, Yokohama, Sagami Bay and Chiba prefecture. Interests in Japan should monitor closely the progress of this storm.


Visible imagery from shortly after sunrise on Tuesday 27 July in Japan shows the storm to the east of Japan; very little convection is within the storm center.

Himawari-8 Visible Image (0.64 µm), 0024 UTC 27 July 2021

Metop-A overflew Japan at around 1040 UTC on 27 July. Scatterometry (source) showed the wind structure of the storm very nicely.

MetopA Scatterometer winds, 1041 UTC on 27 July 2021 (Click to enlarge)

Blowing dust across Mongolia and China

May 6th, 2021 |

Himawari-8 Dust RGB images [click to play animation | MP4]

Himawari-8 Dust RGB images [click to play animation | MP4]

JMA Himawari-8 Dust RGB images (created using Geo2Grid) covering the 48-hour period from 21 UTC on 04 May to 21 UTC on 06 May 2021 (above) revealed multiple plumes of blowing dust (brighter shades magenta/pink) which originated over parts of Mongolia — and were then transported southeastward and eastward across northeastern China.

Surface analyses from the Korean Meteorological Agency (below) showed an impressive pressure gradient between a midlatidude cyclone (moving southeastward from Mongolia into China) and high pressure moving southward behind it. Some of the airborne dust was entrained into the circulation of this low pressure system.

Surface analyses during the period from 21 UTC on 0 May to 21 UTC on 06 May [click to enlarge | MP4]

Surface analyses during the period from 21 UTC on 04 May to 21 UTC on 06 May [click to enlarge | MP4]

VIIRS True Color RGB mages from Suomi NPP and NOAA-20 viewed using RealEarth (below) showed the hazy arc of blowing dust along the trailing cold front (south of the cyclone in northeastern China) on 6 May.

VIIRS True Color RGB mages from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS True Color RGB mages from Suomi NPP and NOAA-20 [click to enlarge]

Rapid intensification of Super Typhoon Surigae

April 16th, 2021 |

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

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

2.5-minute interval rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images (above) showed Typhoon Surigae undergoing rapid intensification (ADT | SATCON) to become a Category 4 storm as of 18 UTC on 16 April 2021.

A DMSP-16 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) displayed a well-defined eye, with distinct spiral bands feeding into the eyewall.

DMSP-16 SSMIS Microwave (85 GHz) image at 1944 UTC [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) image at 1944 UTC [click to enlarge]

After sunrise, Himawari-8 “Red” Visible (0.64 µm) images (below) showed the relatively compact eye, with hints of low-level mesovortices within the eye.

JMA Himawari-8 "Red" Visible (0.64 µm) images [click to play animation]

JMA Himawari-8 “Red” Visible (0.64 µm) images [click to play animation]

===== 17 April Update =====

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

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

The prolonged period of rapid intensification continued overnight, and as of 12 UTC on 17 April Surigae had become a Category 5 Super Typhoon — 2.5-minute interval rapid scan Himawari-8 Infrared images (above) showed the well-defined eye as the storm tracked northwestward across the Philippine Sea (just east of the Philippines). A faster animation (GIF | MP4) helped to highlight the trochoidal motion (wobble) of the eye — a behavior often seen with intense tropical cyclones. The 21 UTC advisory from JTWC listed sustained winds of 165 knots (and objective intensity estimates from ADT and SATCON were around 170 knots), making Surigae the only tropical cyclone on record to reach that intensity during the month of April.



An animation of Himawari-8 Infrared images with an overlay of deep-layer wind shear (below) indicated that Surigae was moving through a region of low to moderate wind shear; the storm was also moving across very warm water (SST + OHC).

Himawari-8 Infrared images, with contours of deep-layer wind shear at 18 UTC [click to enlarge]

Himawari-8 Infrared images, with contours of deep-layer wind shear at 18 UTC [click to enlarge]

Around the time that Surigae was reaching its peak intensity, a Suomi NPP VIIRS Day/Night Band (0.7 µm) image several hours before sunrise (below) revealed concentric mesospheric airglow waves (reference) propagating away from the energetic Category 5 tropical cyclone.

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

In closer view of time-matched Himawari-8 Infrared and Suomi NPP Day/Night Band images (below), a cluster of bright DNB pixels highlighted the presence of lightning activity along the inner edge of the northern eyewall.

Himawari-8 Infrared Window (10.4 µm) and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Himawari-8 Infrared Window (10.4 µm) and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]