Kompasu skirts to the north of Luzon

October 11th, 2021 |
Himawari-8 clean window infrared (band 13, 10.4 µm) imagery, 0232 – 1502 UTC on 11 October 2021

Severe Tropical Storm Kompasu moved westward just north of the island of Luzon in the Philippines on 11 October. The Himawari-8 Target Sector clean window infrared (Band 13, 10.4 µm) imagery, above, from 0232 – 1502 UTC (Imagery courtesy JMA; imagery available here), shows deep convection becoming more organized as the storm center moved.

Moderate wind shear that had been affecting Kompasu slowly relaxed in the 24 hours before the storm moved north of Luzon, as shown in the wind shear tendency map shown below (imagery obtained from this link at the CIMSS Tropical Website). Shear over/around the storm has been relaxing.

Wind shear tendency, 1500 UTC 10 October 2021 – 1200 UTC 11 October 2021 (click to enlarge)
Wind shear over the western Pacific, 1200 UTC 10 October – 1200 UTC 11 October 2021 (Click to enlarge)

Computed shear (imagery also taken from the CIMSS Tropical Website) is shown in the animation above. Wind shear for both animations above is defined here. A relatively small area of favorable wind shear was near the storm center as Kompasu became better organized in the band 13 imagery above.

Scatterometry imagery, below, from various satellite platforms at this site, tracked the system’s motion from 0100 to 1130 UTC on 11 October, as it moved north of Luzon.

Scatterometer imagery from HY-2B and HY-2C, and from ASCAT A, B and C, between 0100 and 1130 UTC on 11 October (2021)

Kompasu is forecast to move due west across the South China Sea in the next days, affecting the island of Hainan on the 13th before 1200 UTC. (Forecast, from JTWC; Here is a similar plot from JMA). Wind shear is not forecast to relax further in the next days so significant stregthening is not forecast.

TROPICS Pathfinder view of super typhoon Mindulle

September 26th, 2021 |
TROPICS Pathfinder 205 GHz imagery, 0545 UTC on 26 September 2021 (Upper Left) and Himawari-8 Band 3 Visible (0.64 µm) Imagery, 0540 UTC on 26 September (Lower Right) (Click to enlarge)

Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) Pathfinder imagery from 0545 UTC on 26 September, when super typhoon Mindulle was near peak intensity, is compared above to Himawari-8 visible(0.64 µm) imagery at about the same time. A separate image links small features in the Pathfinder image to small convective elements that are apparent in the Himawari imagery. Click here to view the TROPICS Pathfinder image with a NOAA-20 true-color image from 0426 UTC.

The pathfinder satellite that provided the microwave data used for the image above is the first in a series of a constellation of low-Earth orbiters; six additional satellites will be launched next year. These are very small satellites, with a size of 10 cm x 10 cm x 36 cm. They weigh in at 5.34 km / 11.8 pounds! Pathfinder imagery was provided courtesy of the Science Team working with the data. Himawari-8 imagery are courtesy of JMA.

Ephemeral Theresa

September 25th, 2021 |
Suomi-NPP Day Night Band Visible (0.7 µm) and M15 (10.8 µm) imagery, 0618 UTC on 25 September 2021 (Click to enlarge)

Theresa was a short-lived subtropical storm in the Atlantic Ocean north of Bermuda late on the 24th and early on the 25th of September. When Suomi NPP overflew the storm early on the 25th (imagery from this source), the low-level circulation was devoid of any significant convection; convection was displaced to the northeast of the storm. The toggle below of True-color imagery from CSPP Geosphere shows the storm structures at 1800 UTC on the 24th and 25th. Convection was nearly wrapped around the subtropical storm on the 24th; it was mostly absent near the storm center on the 25th.

CSPP Geosphere True Color Imagery at 1800 UTC on 24 and 25 September 2021 (Click to enlarge)

Note in the Day Night Band imagery at top that a dark region exists within the moonglint at around 29 N Latitude. Such features, discussed in this blog before (here and here, for example), suggest very light winds; an HY-2C overpass at 0330 UTC on 25 September, shown below (from this site; click here to see a similar image with wind flags), shows very light winds over/around 30 N.

HY-2C Scatterometry at 0330 UTC on 25 September 2021 (Click to enlarge)

Ida, Ascat and Turbulence

August 27th, 2021 |
GOES-16 Band 2 (0.64 µm), Band 13 (10.3 µm) and ASCAT winds, 1406 UTC on 27 August 2021 (Click to enlarge)

At 1400 UTC on 27 August, strengthening tropical storm Ida sat south of Cuba, near the Isle of Youth, and is shown above in both visible and infrared imagery; brightness temperatures are as cold as -87 C in the image above. Note also that the surface circulation is southeast of the coldest cloud tops, perhaps as a result of the shear (click here; analysis from the CIMSS Tropical Website) over the system. (Added: Ida made landfall as a hurricane on the Isle of Youth at 1800 UTC).


Perhaps not surprisingly, the convection in/around the tropical cyclone is diagnosed by a Turbulence prediction product (developed using machine-learning incorporating water vapor imagery, GFS stability, and airline observations of EDR (eddy dissipation rate)) as a very likely region of turbulence. This turbulence product is also available online here (where turbulence observations are included) where it looks like this.

GOES-16 Band 2 (0.64 µm), Band 13 (10.3 µm) and MOG Turbulence Probability, 1406 UTC on 27 August 2021 (Click to enlarge)

For more information on Hurricane Ida, including its potential threat to the central Gulf Coast late in the weekend, refer to the National Hurricane Center.