JMA Himawari-8 “Red” Visible (0.64 µm) images (above) showed trains of vortices extending downwind (southeast) of the Kuril Islands on 28-29 July 2020 (surface analyses). One unusual aspect of these features was the development of small cloud elements within the cloud-free “hole” portion of some of the vortices.

H/T to Santiago Gassó for alerting us to this interesting case.

Himawari animation (fwd/bkwd) confirms it, condensation starts inside the clean holes which remain as cloud after the surrounding dissipates. @CIMSS_Satellite @GOESguy https://t.co/BLx2hqKdEo pic.twitter.com/PW6xNHQsWd

— Santiago Gassó (@SanGasso) July 29, 2020

View only this post Read Less

MIMIC TPW rocking animations from 17-27 July 2020 (and back) [click to play mp4 animation]

Morphed Microwave Imagery at CIMSS (MIMIC) estimates of Total Precipitable Water are derived from microwave sensors such as AMSU and ATMS on different polar-orbiting platforms. MIRS retrievals are used to estimate Total Precipitable Water from each polar swath, and those swaths are then advected forwards and backwards by GFS model winds. In this way, global coverage is achieved; each point on the globe is influenced most by the closest polar pass that most recently sensed the atmosphere. In some cases, that closest pass might occur after the time of the image. Thus, final images in this animation will change with time until about 16 hours after the time of an image. (You can find a training video on this product here, and data are available online here).

The animation above (click here for an animated gif) shows hourly data for ten days ending late on 27 July; during this time, Hurricane Douglas formed and moved just north of the Hawai’ian island chain. The rocking animation clearly shows the initial impulse for Douglas emerging out of the Intertropical Convergence Zone south of Mexico and moving west-northwestward towards Hawai’i. One can speculate on the effect of the moisture associated with Pacific Tropical Depression 7E, which disturbance formed just before Douglas and to its west, had on Douglas’ structure as it moved north of Hawai’i. Did that extra moisture help?

Ten-day rocking animations of MIMIC are routinely available for the eastern Pacific, for North America and for Australia.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed  Category 1 Hurricane Douglas as it moved just north of Hawai’i during the day on 26 July 2020 (the boundary of the Mesoscale Sector was abruptly shifted westward at 1658 UTC). The coldest cloud-top infrared brightness temperatures were around -80ºC.

The apparent storm center as seen in satellite imagery was shifted north of the actual surface center location, due to the presence of southerly/southwesterly deep-layer wind shear as shown by a 20 UTC analysis from the CIMSS Tropical Cyclones site (above). This offset was also evident in a comparison of a DMSP-17 SSMIS Microwave (85 GHz) image at 1711 UTC with the analyzed surface position of Douglas at 1800 UTC (below).

===== 27 July Update =====

GOES-17 Visible and Infrared images (above) showed that the low-level circulation became exposed from the deep convection of Douglas a few hours after sunrise on 27 July, as it moved southwestward near the island of Nihoe. An analysis of deep-layer wind shear at 22 UTC (below) indicated the presence of 25-30 knots of southwesterly shear over that area — an unfavorable environment for tropical cyclone intensification/maintenance, in spite of the fact that the storm was moving over favorably-warm water.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed Category 1 Hurricane Hanna making landfall along the South Coast of Texas at 2200 UTC on 25 July 2020. The coldest cloud-top infrared brightness temperature was -88.6ºC at 1633 UTC. Winds gusted to 76 mph at Buoy 42020, and at 18 UTC a ship about 30 miles off the Texas coast reported blowing spray.

GOES-16 GLM Flash Extent Density (below) showed little to no lightning activity within the immediate eyewall region of Hurricane Hanna during the 9 hours leading up to landfall; however, lighting did increase somewhat after the 22 UTC landfall.

A comparison of time-matched Infrared images from Suomi NPP and GOES-16 ABI (below) showed the effect of parallax displacement, even at the relatively low latitudes of South Texas. The coldest cloud-top infrared brightness temperature on the VIIRS image was -86ºC, compared to -81ºC on the ABI image (the same color enhancement is applied to both images).

View only this post Read Less