Snowfall in southern Texas

December 8th, 2017 |

GOES-13 Visible (0.63 µm, left) and Shortwave Infrared (3.9 µm, right) images, with hourly plots of surface reports [click to play animation]

GOES-13 Visible (0.63 µm, left) and Shortwave Infrared (3.9 µm, right) images, with hourly plots of surface reports [click to play animation]

The combination of lift from an upper-level trough and cold air behind the passage of a surface cold front  set the stage for accumulating snow across far southern Texas on 08 December 2017. As the clouds cleared, GOES-13 (GOES-East) Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (above) revealed a narrow swath of snow cover running northeastward from the Rio Grande River toward Corpus Christi — the highest snowfall total associated with this feature was 7.0 inches near Corpus Christi. Daily snowfall records included 0.3 inch at Brownsville and 1.0 inch at Corpus Christi.

A toggle between Terra MODIS true-color and false-color Red-Green-Blue (RGB) images from RealEarth (below) showed the southwestern portion of this band of snow cover (which appeared as darker shades of cyan in the false-color image).

Suomi NPP VIIRS true-color and false-color RGB images [click to enlarge]

Suomi NPP VIIRS true-color and false-color RGB images [click to enlarge]

Farther to the north, another southwest-to-northeast oriented band of snow cover was seen on Terra MODIS true-color and false-color RGB images (below), stretching from San Antonio to Austin to College Station. The highest snowfall total there was 5.0 inches (NWS Austin/San Antonio summary),

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

Hurricane Ophelia

October 14th, 2017 |

GOES-13 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images, with hourly surface reports (in metric units) plotted in yellow [click to animate]

GOES-13 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images, with hourly surface reports (in metric units) plotted in yellow [click to animate]

Hurricane Ophelia — the record-tying 10th consecutive Atlantic basin hurricane of the 2017 season — reached a satellite-estimated Category 3 intensity at 15 UTC on 14 October 2017. GOES-13 (GOES-East) Visible (0.63 µm) and Infrared Window (10.7 µm) images (above) showed a well-defined circular eye as the storm moved well south of the Azores. The tweet below underscores the unusual nature of the intensity and location of Ophelia (which also occurred over unusually-cold waters).

A DMSP-17 SSMIS Microwave (85 GHz) image (below) also revealed a circular eye structure.

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

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

One factor that might have aided this increase of intensity was the recent passage of Ophelia through an environment of higher Maximum Potential Intensity (reference), where maximum wind speed values of 100 knots resided (below).

Maximum Potential Instability wind speed plot from 13 October, with the track of Ophelia as of 18 UTC on 14 October [click to enlarge]

Maximum Potential Instability wind speed plot from 13 October, with the track of Ophelia as of 18 UTC on 14 October [click to enlarge]

Hurricane Nate makes landfall in Louisiana and Mississippi

October 7th, 2017 |

GOES-16 Visible (0.64 µm. left) and Infrared Window (10.3 µm, right) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm. left) and Infrared Window (10.3 µm, right) images, with hourly surface reports plotted in yellow [click to play MP4 animation]

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

1-minute interval Mesoscale Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the large central dense overcast (which exhibited cloud-top infrared brightness temperatures of -80ºC and colder, violet colors, and at times -90ºC and colder, yellow enhancement) and subsequent smaller convective bursts associated with Hurricane Nate on 07 October 2017.

After having moved north-northwestward at speeds up to 24 mph — quite possibly the fastest-moving tropical cyclone on record in the Gulf of Mexico — Nate made its initial landfall (as a Category 1 storm) in Louisiana near the mouth of the Mississippi River at 00 UTC on 08 October 2017 [note: Nate’s second landfall was around 0530 UTC near Biloxi, Mississippi]. A few reports of damaging winds and tornadoes were noted ahead of and during Nate’s landfall; a listing of other wind gusts can be seen here.

Earlier in the day, DMSP-17 SSMIS Microwave (85 GHz) imagery was hinting at the development of a closed eye structure beneath the central dense overcast seen on GOES-13 Infrared Window (10.7 µm) imagery (below).

GOES-13 Infrared Window (10.7 µm) and DMSP-17 SSMIS Microwave (85 GHz) images around 1215 UTC [click to enlarge]

GOES-13 Infrared Window (10.7 µm) and DMSP-17 SSMIS Microwave (85 GHz) images around 1215 UTC [click to enlarge]

Even though Nate passed over very warm water in the Gulf of Mexico (below), the fast forward motion of the storm limited its ability to take advantage of those warm waters and rapidly intensify.

Sea Surface Temperature and Ocean Heat Content analyses from 06 October, with an overlay of the 07 October path of Hurricane Nate ending at 12 UTC [click to enlarge]

Sea Surface Temperature and Ocean Heat Content analyses from 06 October, with an overlay of the 07 October path of Hurricane Nate ending at 12 UTC [click to enlarge]

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.