MIMIC Total Precipitable Water fields, above, (archived here), show the motion of Typhoon Bolaven as it evolved from a strong typhoon west of 150^o E Longitude on 10 October to a potent extratropical cyclone approaching 150^oW Longitude on 16 October 2023, at which later time a long filament of tropical moisture continued to accompany the system. True Color imagery from the CSPP Geosphere site, below, shows the elongated system with the cold front stretching to the west-southwest.

MIMIC TPW fields over the eastern Pacific at 1800 UTC on 16 October, below, show two different moist airstream; one is affecting the Pacific Northwest of the USA (and southwestern Canada) at 1800 UTC. The moisture with the remains of Bolaven is approaching from the west. The GFS model initialized on 1200 UTC on 16 October suggests the next 72 hours will be wet along Coastal British Columbia with widespread rainfalls of 4-6″ (link, from this site) .

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GOES-18 Air Mass RGB images from 14-16 October (above) showed the period during which Typhoon Bolaven made its extratropical transition to a Hurricane Force Low on 14 October and then to an expansive Storm Force Low on 16 October (surface analyses from OPC). The brighter shades of orange-red in the RGB imagery depicted a Potential Vorticity anomaly associated with this strong storm system. 

At 2100 UTC on 16 October, a cross section of AK-NAM40 model Potential Vorticity and Wind Speed along Line J-J’ (below) highlighted a well-defined tropopause fold, descending into the middle troposphere below the core of a 130-140 knot jet stream (the jet axis was situated along the southern periphery of the storm).

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The storm has generated a particularly large wind field, as shown below (from this website). Between 0650 and 0834 UTC, when Metop-B (twice) overflew the area, the Advanced Scatterometer detected a very large region of 30-35 knot winds (red in the enhancement), with peak winds near 45 knots near 40^oN, 153^oW.

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10-minute Full Disk GOES-16 (GOES-East) CIMSS Natural True Color RGB images created using Geo2Grid (above) showed the 2023 Annular Solar Eclipse shadow as it progressed southeastward from the Pacific Northwest to Brazil on 14 October 2023.

GOES-16 Near-Infrared “Vegetation” (0.86 µm) images — in the native projection of the GOES-16 satellite (below) — provided another view of the eclipse shadow path.

A staggered set of three Mesoscale Domain Sectors from GOES-18 (GOES-West) provided 1-minute imagery of the eclipse shadow progression (below).

GOES-16 SUVI Fe171 images from the SSEC Geostationary Satellite Imagery site (below) showed the Moon’s silhouette as it passed in front of the Sun during the eclipse period.

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Tropical Storm Sean has developed in the mid-Atlantic and is moving northwest, but is predicted to dissipate by Sunday, 2023-10-15. RealEarth provides an opportunity to look back at the last 48 hours of Sean developing. A video from RealEarth shows GOES-16 true color and Band 13 (10.3 microns, “clean” infrared band) from 2023-10-11 at 1525Z to 2023-10-13 at 1525Z. While signs of convection are apparent on 2023-10-12, the storm structure appears dissipated by the daylight hours of 2023-10-13 when viewing at these wavelengths.

Investigating the finer details of Sean on 2023-10-13, Band 9 (6.95 microns, mid-level water vapor) is examined. A storm structure is hardly noticeable. What stands out in the Atlantic even more in the Band 9 animation is an unnamed disturbance to the East of Sean. (These are the red areas in the Band 9 animation.) The National Hurricane Center predicts this system of having a 10% chance of forming a cyclone in the next 48 hours.

The MIMIC Total Precipitable Water product, below, provides a look back at the last 24 hours of their TPW field. When examining TPW, a more cyclonic structure appears. The TPW field seems to show some actual rotation in Sean, which is harder to notice in the GOES animations.

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The Lightning Imaging Sensor (LIS) has been flying on the International Space Station since 2017 to extend LIS observations that began with the Tropical Rainfall Measurement Mission (TRMM). This provides for nearly global observations optical detection of lightning. On 11 October and 12 October, two passes of the LIS, shown below, observed Typhoon Bolaven: the ascending pass from 2124 to 2134 UTC on 11 October, and the descending pass from 0716 to 0728 UTC on 12 October. What kind of lightning was observed and where was it observed in relation to the Typhoon?

The observations at ca. 2130 UTC on 11 October 2023 are overlain on the AWIPS plot below. Three separate groups are apparent, and we’ll focus on the two more southerly clusters that include 23 separate flash observations.

The southwesternmost cluster has 6 flashes in a region between 20.15^o-20.33^oN and 142.76^o-142.91^oE. The northeastern cluster has 17 flashes near 21.87^oN 144.98^oE. Where are these flashes relative to the storm?

As indicated below, the lightning detected by LIS with this system is in the southwestern eyewall of the storm, and within a vigorous outer band. (For a recent study on the relationship between lightning and storm intensity, click here; an earlier study is here)

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What happened on 12 October? LIS observed 8 lightning flashes between 0718-0720 UTC in a region near 21.85^oN, 143.65^o E.

Where were the lightning observations in relation to the Typhoon? As at 2130 UTC on 11 October, lightning activity was detected right in the eyewall of the storm, as indicated below.

In both cases, LIS observed lightning within the eyewall of Bolaven. Such observations are consistent with the system’s strength.

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