The Active Atlantic Basin in August and September

October 4th, 2017 |

ABI “Clean Window” Infrared (10.3 µm) Image, 1800 UTC on 8 September 2017, showing Katia, Irma and Jose, from left to right (Click to animate as a YouTube Video)

The YouTube link, above, shows the GOES-16 “Clean Window” (10.3 µm) Infrared Imagery over the Atlantic, showing the evolution of Hurricanes Franklin through Maria, from 7 August through 1 October. (The original mp4 video (250 Meg) is available.)

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

September 2017: a record-setting month in terms of Atlantic tropical cyclone ACE

October 4th, 2017 |

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

The Accumulated Cyclone Energy (ACE) for September 2017 set a new record for any month over the North Atlantic basin:

Two significant contributors to this record ACE value were long-lived and very intense Hurricane Irma and Hurricane Maria.

Hurricane Irma – Ace: 66.6 – Duration: 13 Days

Montage of Hurricane Irma GOES-13 infrared images, with and without storm track/intensity [click to view]

Montage of Hurricane Irma GOES-13 infrared images, with and without storm track/intensity [click to view]

One noteworthy statistic of Hurricane Irma: during its 3 days and 3 hours as a Category 5 hurricane (above), the storm had an intensity of 160 knots or 185 mph for 37 consecutive hours — which set a new world record. GOES-16 “Clean” Infrared Window (10.3 µm) images during this period of 185 mph intensity (below) showed a well-defined eye, with cold cloud-top infrared infrared brightness temperatures (occasionally -80ºC or colder, denoted by the violet color enhancement) within the adjacent eyewall region.

GOES-16 Infrared Window (10.3 µm) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

Hurricane Maria – Ace: 44.6 – Duration: 14 Days

Montage of Hurricane Maria GOES-13 infrared images, with and without storm track/intensity [click to view]

Montage of Hurricane Maria GOES-13 infrared images, with and without storm track/intensity [click to view]

One noteworthy aspect of Hurricane Maria was its intensification to a Category 5 storm on 18 September (above) — just before making landfall on the island of Dominica — and less than 48 hours before making landfall over southeastern Puerto Rico as a high-end Category 4 storm. GOES-16 Infrared Window (10.3 µm) images at 1-minute (pre-landfall) and 30-second (post-landfall) time intervals (below) showed that while the eye of Maria quickly eroded as the tropical cyclone moved northwestward across the island and interacted with its rugged terrain, deep convection of the eyewall region persisted over much of Puerto Rico during the transect. Note that the last hourly surface observations from Roosevelt Roads (TJNR) and San Juan (TJSJ) were from 04 UTC and 09 UTC, respectively — after which times power and communications to weather equipment (such as the San Juan radar) were lost.

GOES-16 Infrared Window (10.3 µm) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

Hurricane Jose – Ace: 42.2 – Duration: 17 Days

Montage of Hurricane Jose GOES-13 infrared images, with and without storm track/intensity [click to view]

Montage of Hurricane Jose GOES-13 infrared images, with and without storm track/intensity [click to view]

Although not as intense as Irma or Maria, the long duration of Hurricane Jose allowed it to achieve an ACE value nearly as high.

Individual storm montage images are available here on the CIMSS Tropical Cyclones site.

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]

Maria: Tropical Storm Watch for the Outer Banks of North Carolina

September 24th, 2017 |
Track of Hurricane Maria [click to enlarge]

Track of Hurricane Maria [click to enlarge]

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

Hurricane Maria was downgraded to a Category 2 storm at 12 UTC on 24 September 2017 (above), when it was located about halfway between Miami and Bermuda.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed a close-up view of the eye region of Maria during the daylight hours.

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]

Due to the large size of the radius of Tropical Storm force winds, a Tropical Storm Watch was issued late in the day for the Outer Banks and adjacent inland areas of North Carolina (below).

NHC advisory

UPDATE: 12 hours later, much of the Tropical Storm Watch was upgraded to a Tropical Storm Warning.