Hurricane Teddy and wildfire smoke

September 22nd, 2020 |

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 (GOES-East) True Color Red-Green-Blue (RGB) images created using Geo2Grid (above) revealed that the large circulation of Hurricane Teddy (downgraded from a Category 2 to a Category 1 storm at 18 UTC) was drawing hazy filaments of smoke — likely originating from wildfires in the western US — southward from eastern Canada and New England, carrying it across the far western Atlantic Ocean on 22 September 2020. Also of interest (early in the animation) were the narrow fingers of river valley fog across parts of New York, Pennsylvania, Maryland, West Virginia and Virginia.

Although the size of Teddy’s cloud shield was still fairly large, a DMSP-17 SSMIS Microwave (85 GHz) image at 2217 UTC from the CIMSS Tropical Cyclones site (below) showed that no organized core of deep convection remained as the storm began to move across colder waters (Sea Surface Temperature | Ocean Heat Content) and encounter a more hostile environment of increasing deep-layer wind shear.

DMSP-17 SSMIS Microwave (85 GHz) image at 2217 UTC [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) image at 2217 UTC [click to enlarge]

GOES-16 CIMSS Natural Color RGB images, with and without an overlay of Aerosol Optical Depth [click to play animation | MP4]

GOES-16 CIMSS Natural Color RGB images, with and without an overlay of Aerosol Optical Depth [click to play animation | MP4]

A larger-scale view of GOES-16 CIMSS Natural Color RGB images — with and without an overlay of Aerosol Optical Depth (above) showed that an elongated plume of smoke stretched westward from New York and Pennsylvania to parts of Wisconsin, Illinois and Iowa. Upward-looking lidar data from the University of Wisconsin – Madison (below) depicted a thick layer of smoke between altitudes of 2-6 km.

Plots of lidar backscatter and depolarization from 12 UTC o n 22 September to 00 UTC on 23 September [click to enlarge]

Plots of lidar backscatter (top) and depolarization (bottom) from 12 UTC on 22 September to 00 UTC on 23 September [click to enlarge]

Tropical Storm Beta in the Gulf of Mexico

September 20th, 2020 |

GOES-16 Imagery and Derived Motion winds at 1346 UTC on 20 September 2020 (Click to enlarge). ABI Imagery includes Visible (Band 2, 0.64 µm), the near-infrared ‘Cirrus’ (Band 4, 1.38 µm) and the upper water vapor (Band 8, 6.19 µm) and lower water vapor (Band 10, 7.34 µm) infrared imagery. Derived motion winds for 1346 UTC near 1000 mb (green), 850 mb (yellow), 700 mb (orange), 500 mb (cyan) and 300 mb (purple) are also shown

Tropical Storm Beta was in the northwest Gulf of Mexico on 20 September 2020. Visible imagery (with GLM overlain) shows two principal regions of convection, one near the center, and one in a long feeder band to the east of the storm. Derived motion winds (this image includes a legend that links vector color to level) show cyclonic low-level motion in the northwest Gulf of Mexico, divergent motion at 500 mb, and strong westerly outflow at 300 mb.

‘Cirrus Channel’ (Band 4, 1.38 µm) near-infrared imagery shows the considerable upper-level cloudiness associated with the central convection and the convective band east of the center. There is also abundant storm outflow to the east and north of the storm.

Visible imagery and low-level winds show cyclonic motion at low levels.  The convection is displaced to the east because of southwesterly shear over the storm (shown below, in an image take from this site).

200-850 mb wind shear over the Gulf of Mexico, 1400 UTC on 20 September 2020 (click to enlarge)

Both upper-level and low-level water vapor imagery show very dry mid-tropospheric air over Texas. MIMIC Total Precipitable Water, below, (source), also shows the significant dry air over the continent. (Hurricane Teddy is also apparent in the western Atlantic).

Hourly MIMIC Total Precipitable Water estimates for the 24 hours ending 1400 UTC on 20 September 2020 (Click to enlarge)

Is the dry air influencing the development of this storm? Low-level flow (850-700), below, from this site, shows weak easterly flow. Low-level flow is from regions of deep moisture. Upper-level flow (200-700 mb) shows motion from the (dryer) west. These two different airflows are influencing the development of Beta.

Mean 850-700 mb flow at 1200 UTC, 20 September 2020 (Click to enlarge)

Mean 700-200 mb flow at 1200 UTC, 20 September 2020 (Click to enlarge)

For the latest on Beta, refer to the pages of the National Hurricane Center (direct link for Beta).

Hurricane Teddy rapidly intensifies to a Category 4 storm

September 17th, 2020 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images — with and without an overlay of GLM Flash Extent Density (above) showed Hurricane Teddy as it rapidly intensified (ADT | SATCON ) to a Category 4 storm on 17 September 2020. The coldest cloud-top infrared brightness temperatures were in the -80 to -85ºC range.

Metep-A ASCAT surface scatterometer wind speeds were as high as 74 knots in the northwestern portion  of the eyewall (below).

GOES-16 “Red” Visible (0.64 µm) image, with plots of Metop-A ASCAT winds [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) image, with plots of Metop-A ASCAT winds [click to enlarge]

Microwave (85 GHz) DMSP-17 (at 1023 UTC), GMI (at 1720 UTC) and DMSP-18 (at 2034 UTC) images from the CIMSS Tropical Cyclones site are shown below.

DMSP-17 SSMI Microwave (85 GHz) image at 1023 UTC [click to enlarge]

DMSP-17 SSMI Microwave (85 GHz) image at 1023 UTC [click to enlarge]

GMI Microwave (85 GHz) image at 1720 UTC [click to enlarge]

GMI Microwave (85 GHz) image at 1720 UTC [click to enlarge]

DMSP-18 SSMI Microwave (85 GHz) image at 2034 UTC [click to enlarge]

DMSP-18 SSMI Microwave (85 GHz) image at 2034 UTC [click to enlarge]

Medicane approaching Greece

September 17th, 2020 |

Daily VIIRS True-Color images over the central Mediterranean Sea, 14 – 19 September 2020 (Click to enlarge)

A Medicane (a portmanteau of Mediterranean and Hurricane) has developed in the central Mediterranean Sea, and moved northeastward through the Ionian Sea towards Greece and Albania. Daily snapshots of VIIRS true-color imagery, above, from NASA Worldview, show a slow increase in organization. (Previous CIMSS Blog Posts on Medicanes are here, here and here.) This Medicane was given the name ‘Ianos’.

There is an isolated region of small values of wind shear over this system (1800 UTC image from 17 September, from this website), as expected for a tropical storm.  An image of hourly CMORPH precipitation values, below, show heavy precipitation associated with the storm as well.

CMORPH Hourly Precipitation ending 1700 UTC on 17 September 2020 (Click to enlarge)

The ASCAT instrument on Metop-B observed a very tight cyclonic circulation on 16 September, as shown below (imagery from this site).

Metop-B ASCAT winds, 16 September 2020 (Click to enlarge)

MIMIC Total Precipitable Water (TPW) (below, from this site) shows a compact swirl around the storm, with large values of TPW.

MIMIC Total Precipitable Water for the 24 hours ending 2000 UTC on 17 September 2020 (click to enlarge)


NASA’s IMERG product showed the heavy rain that was associated with this storm as it moved towards Greece.