Himawari-9 airmass RGB imagery, above, shows the extratropical transition of Typhoon Ampil. At the beginning of the animation, the typhoon is approaching Japan from the south. By 0000 UTC on 17 August, the typhoon has moved east of Japan, and a Potential Vorticity anomaly just west of the storm (identifiable by the orange hue in the RGB) suggests the storm is starting to become extratropical. By 0000 UTC on 19 August, a second mid-tropospheric potential vorticity anomaly (also identifiable by its orange hue in the RGB), is moving over Kamchatka and the Kuril Islands just west of the evolving typhoon and being incorporated into the storm. Airmass RGBs are a useful product in highlighting the possibility of a rapid transition of typhoons to a strong extratropical storm (another example is 2022’s Typhoon Merbok).

Merbok was a very intense storm after it became extratropical, far stronger and damaging than Ampil. One notable difference between the two storms was the connection between the storms and tropical moisture. MIMIC Total Precipitable Water fields for Merbok, below, at 1200 UTC on 14-15 September 2022 (source), show a connection to the rich moisture of the Intertropical Convergence Zone (a MIMIC TPW animation is also available here, from this blog post). That direct connection is missing for Ampil, and might be one of many reasons for the differences in extratropical storm strength.

Thanks to Eddie Zingone, WFO ANC for mentioning Ampil’s extratropical transition on a telecon this week!

View only this post Read Less

Typhoon Ampil was at the northern edge of the view of the Direct Broadcast antenna at the forecast office on Guam, and CSPP software processed the above images (courtesy Douglas Schumacher) showing the ample eye of the Typhoon. Microwave imagery suggests an eyewall that is not quite complete, especially on the western side. MIMIC imagery below (from here) suggests an incomplete eyewall as well.

Hourly imagery from 1140 (just after the NOAA-19 overpass shown above) through 1840 UTC show cold cloud tops not quite continuously encircling Ampil’s eye. The GK2A imagery below was created using geo2grid imagery and level-1b GK2A data from KMA.

See the Tokyo Regional Specialized Meteorological Center (RSMC) or the USA’s Joint Typhoon Warning Center for the latest on Ampil. The storm is forecast to make a very close approach to Japan before turning eastward out to sea.

View only this post Read Less

VIIRS imagery from Suomi NPP and NOAA-20, above, show the structure of Hurricane Ernesto as it pulls away from Puerto Rico. Dry air is entrained within the storm, as evidenced by the regions near the center where convection is absent. Sea-surface temperatures in the region are quite warm, however, and shear is small, as shown below: strengthening is forecast.

Ernesto is tucked within the southeast corner of the GOES-16 CONUS sector field of view. Five-minute GOES-16 Low-Level Water Vapor infrared imagery (Band 10, 7.34 µm) and GLM observations of Flash-Extent Density, below, show very warm brightness temperatures over the Greater Antilles. MIMIC Total Precipitable water fields (at bottom) show dry air there as well. The future intensity of Ernesto will be directly affected by how much of the dry air continues to infiltrate into the storm circulation. Lightning observations at this time were mostly confined to Ernesto’s outer bands.

For the latest information on Ernesto, refer to the National Hurricane Center: https://www.nhc.noaa.gov .

View only this post Read Less

Tropical Cyclone’s Debby slow progress up the east coast of the US (Blog Post) resulted in a prolonged rain event. The slider above compares the Susquehanna River on 1 August (a clear day before Debby) and on 13 August, after the inundation. The turbidity of the river, and its discharge into Chesapeake Bay increased enough to be obvious to satellite detection.

Data from the USGS Gauge at Harrisburg, below, shows the heavy rain (especially on 9 August), the increase in river height, and the large increase in river flow for the week ending 13 August 2024.

Thanks to Dave Zaff, NWS Eastern Region HSD, for alerting us to this imagery. Imagery for this post was created with Geo2grid.

View only this post Read Less