Hurricane Maria downgraded to a Tropical Storm off the East Coast

September 26th, 2017 |
GOES-13 Infrared Window (10.7 µm) image, with Deep-Layer Wind Shear product [click to enlarge]

GOES-13 Infrared Window (10.7 µm) image, with Deep-Layer Wind Shear product [click to enlarge]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

After its final 2 days of northward motion as a Category 1 storm well southeast of the Outer Banks of North Carolina, Hurricane Maria was downgraded to a Tropical Storm at 2100 UTC on 26 September 2017. A comparison of the 2345 UTC September GOES-13 (GOES-East) Infrared Window (10.7 µm) image and an overlay of the 00 UTC 27 September Deep-Layer Wind Shear product (above) showed that Maria had been moving northward into an environment of increasing northeasterly shear, aiding the decrease of storm organization and intensity. However, due to the large size of the strong wind field associated with Maria, surface wind gusts as high as 59 mph were reported along the Outer Banks.

The effect of increasing wind shear was obvious in the satellite presentation of GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) — the low-level circulation center (LLCC) was becoming more exposed with time, while deep convection remained southeast of the LLCC.

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images [click to play MP4 animation]

The entrainment of dry air into the northern semicircle of Maria was evident as a warming/drying trend depicted on GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below).

GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

Tropical Storm Don

July 18th, 2017 |

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm) images [click to play MP4 animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

On 17 July Tropical Storm Don became the 4th named storm of the 2017 North Atlantic Basin season. The satellite presentation improved somewhat on 18 July, with GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) displaying a few brief convective bursts (some of which exhibited cloud-top infrared brightness temperatures of -80º C  and colder).

A GOES-13 (GOES-East) Infrared Window (10.7 µm) image at 1845 UTC  with overlays of the Tropical Overshooting Tops and  Deep-Layer Winds products from the CIMSS Tropical Cyclones site is shown below.

GOES-13 Infrared Window (10.7 µm) images, with Tropical Overshooting Top and Deep-Layer Wind Shear products [click to enlarge]

GOES-13 Infrared Window (10.7 µm) images, with Tropical Overshooting Top and Deep-Layer Wind Shear products [click to enlarge]

Hurricane Dora

June 26th, 2017 |

GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images [click to play MP4 animation]

** GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing **

Dora became the first hurricane of the Eastern Pacific 2017 season on 26 June, and was also the first hurricane to be sampled by GOES-16. On Visible (0.64 µm) and Infrared Window (10.3 µm) images (above), Dora displayed an improving appearance as the day progressed — mesovortices were seen within the eye on Visible imagery, while the overall eye/eyewall structure improved as the eye diameter increased on Infrared Window imagery.

Early in the morning, a comparison between DMSP-17 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) images from the CIMSS Tropical Cyclones site (below) showed  that a well-defined eye was more apparent on microwave imagery. Dora was moving over fairly warm Sea Surface Temperatures, and was also in an environment characterized by low values of deep-layer wind shear.

DMSP-17 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) images [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) and GOES-15 Infrared Window (10.7 µm) images [click to enlarge]

Tropical Storm Bret

June 19th, 2017 |

GOES-16 “Veggie” Band (0.86 µm) animation of Tropical Storm Bret, 1545-2030 UTC on 19 June 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

The fast-moving tropical system in the southern Caribbean Sea has developed a closed circulation and has been named Bret.  Tropical Storm Bret, shown above in an animation of GOES-16 Near-Infrared (0.86 µm) imagery that highlights land/water contrasts (the Orinoco River in Venezuela and Caribbean Islands — some with cloud streamers in their lee — north of Venezuela stand out clearly), is forecast to remain very close to the South American coastline.  Such proximity to land will likely hinder development. Further, wind shear in the atmosphere over the storm is predicted to increase.

Bret is embedded within a ribbon of very moist air (associated with the ITCZ) that stretches from Africa to the northwest Caribbean, as shown in the animation below (taken from this site) that shows morphed microwave observations of total precipitable water.

Microwave estimates of Total Precipitable Water for the 24 hours ending 1900 UTC on 19 June 2017 (Click to enlarge)

For more information on Bret, refer to the National Hurricane Center and the CIMSS Tropical Cyclones sites (where you can also follow the future of the system emerging into the Gulf of Mexico).