Cold cloud tops associated with Tropical Storm Surigae in the West Pacific

April 15th, 2021 |

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]

2.5-minute interval rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images (above) revealed intermittent cloud-top infrared brightness temperatures of -100ºC and colder (red pixels embedded within yellow-to-black inner cores) — with the coldest being -101.7ºC at 1342 UTC — within the Central Cold Cover (CCC) pattern of Tropical Storm Surigae on 15 April 2021.

A zoom-in of NOAA-20 VIIRS Infrared Window (11.45 µm) imagery at 1644 UTC as viewed using RealEarth (below) also showed 2 clusters of red -100ºC and colder pixels, with a minimum of -103.6ºC (incidentally, the coldest pixels on the 1644 UTC Himawari-8 Infrared image were -96ºC). About an hour and 15 minutes after this NOAA-20 image, Surigae was upgraded to a Category 1 typhoon (the first typhoon of the 2021 season in the West Pacific basin).

NOAA-20 VIIRSI Infrared Window (11.45 µm) image at 1644 UTC [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 1644 UTC [click to enlarge]

A plot of 12 UTC rawinsonde data from Yap Island showed that the coldest air temperature was -84.7ºC at 100 hPa (16.7 km) — so an overshooting top of -100ºC or colder indicated a significant vertical ascent above the tropopause.

Plot of 12 UTC rawinsonde data from Yap Island [click to enlarge]

Plot of 12 UTC rawinsonde data from Yap Island [click to enlarge]

Tropical Depression (update: Tropical Storm Surigae) over the western Pacific

April 13th, 2021 |

Himwari-8 Clean Window (10.41 µm) Band 13 Infrared imagery, 1220 – 2050 UTC on 13 April 2021 (Click to animate)

Himawari-8 Window Channel infrared imagery (10.41 µm), above, shows a well-defined tropical disturbance (Tropical Depression #2 has become become Tropical Storm Surigae by 0900 UTC on 14 April; this website shows Pacific basin names and includes audio pronunciation examples) moving between Yap and Palau in the western Pacific to the southwest of Guam. The disturbed weather in this region has persisted for many days as it has moved towards the west-northwest, as shown in the rocking MIMIC Total Precipitable Water animation below.

10-day animation of MIMIC Total Precipitable Water over the western Pacific Ocean, 2-12 April 2021 (Click to animate)

NOAA-20 NUCAPS estimates of tropopause Heights, below, show the storm in a region with a very high tropopause, around 120 hPa. The system is moving towards a region with similarly high tropopauses.

Himawari-8 Clean Window (10.41 µm) infrared imagery overlain with NUCAPS estimates of Tropopause Heights, 1540 UTC on 13 April 2021 (Click to enlarge)

Water Vapor imagery (6.24 µm and 7.3 µm) from near sunrise of 14 April show moist air in the immediate environment surrounding the storm (Link).  Visible imagery at sunrise on 14 April, below, show strong and persistent deep convection.

Himawari-8 Visible (0.64 µm) imagery, 2027 – 2114 UTC on 13 April 2021 (Click to enlarge)

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It is interesting to note that during the ~12 hours prior to the disturbance (dubbed Tropical Invest 94W) being named Tropical Depression 02W at 12 UTC on 13 April, 2.5-minute interval Himawari-8 Visible (0.64 µm) images from 0002-0802 UTC (below) revealed a trio of low-level vorticies circulating around the incipient storm center. The northernmost vortex appeared to play a role in the initiation of a small cluster of sheared convection. While an exposed low-level circulation center is common in deteriorating highly-sheared tropical cyclones, the presence of 3 vortices during the formative stages of development is rather unusual.

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

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

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Imagery from the CIMSS Tropical Weather Site (link), below, shows the system in a region of very warm Sea Surface Temperatures and modest shear.  Strengthening is forecast as it moves towards the Philippines.

Screencaptures from the CIMSS Tropical Weather Website ca. 2100 UTC on 13 April 2021 (Click to enlarge)

 

Himawari-8 Imagery courtesy of JMA, the Japan Meteorological Agency.

Heavy rainfall and flooding associated with Tropical Cyclone Seroja

April 4th, 2021 |

MIMIC Total Precipitable Water product [click to play animation | MP4]

MIMIC Total Precipitable Water product [click to play animation | MP4]

The incipient circulation of Cyclone Seroja moved very slowly across the island of Timor in Indonesia during the 03 April – 04 April 2021 period — and the MIMIC Total Precipitable Water product (above) depicted very high values over that area (just northwest of Australia).

At Kupang’s El Tari Airport, precipitation amounts included 547 mm (21.5 inches) during the 48 hours ending at 00 UTC on 05 April — with the heaviest amounts of 106 mm (4.2 inches) in 6 hours and 80 mm (3.1 inches) in 3 hours occurring during the 00-06 UTC period on 04 April when the pressure was falling as Cyclone Seroja began to slowly organize and intensify (below). Flash flooding affected much of the island, with multiple deaths being reported.

Time series plot of surface observations at El Tari Airport, Kupang [click to enlarge]

Time series plot of surface observations at El Tari Airport, Kupang, Indonesia [click to enlarge]

JMA 2.5-minute interval rapid scan Himawari-8 “Clean” Infrared Window (10.4 µm) images (below) revealed a few convective bursts — with cloud-top infrared brightness temperatures of -90ºC and colder (yellow pixels embedded within darker shades of purple) — in the vicinity of Kupang (station identifier WATT) between 04 UTC on 04 April and 00 UTC on 05 April.

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

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

A NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC visualized using RealEarth (below) showed one lone -90ºC pixel within a convective burst centered just north of Kupang.

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC on 04 April [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0550 UTC on 04 April [click to enlarge]


CMORPH estimates of 7-day precipitation (available in RealEarth) over the region show 300-400 mm over West Timor, and values exceeding 700 mm (!!) over the adjacent ocean.

7-day CMORPH accumulation of precipitation ending 0000 UTC 5 April 2021 (Click to enlarge)

Early Spring over the Great Lakes

April 2nd, 2021 |

True-Color imagery derived from VIIRS on board NOAA-20 at 1824 UTC on 2 April 2021 (Click to enlarge)

VIIRS data from the ascending NOAA-20 overpass on 2 April 2021 — with data downloaded at the Direct Broadcast site at UW-Madison — showed predominantly clear skies over the Great Lakes.  Lake ice is confined to bays on the north shore of Lake Superior, and a hint of green appears over southeastern Pennsylvania and southwestern Ohio.  A larger version of this image is available here, for about a week.  VIIRS imagery is routinely available from all recent overpasses and can be viewed here.