Tropical Storm Emily forms in the eastern Gulf of Mexico

July 31st, 2017 |

GOES-16 Visible (0.64 µm) Imagery from 1102-1327 UTC on 31 July 2017 (Click to animate)

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

Tropical Storm Emily has formed in the eastern Gulf of Mexico on 31 July 2017, just to the west of Tampa/St. Petersburg, Florida. Its presence is possibly related to the surface front that has sagged south into Florida over the weekend.  (Sea Surface Temperatures in the area are very warm as well.) In the Visible (0.64 µm) animation above (a slower animation is available here), the curved bands of the low-level cloud field are noticeable just northwest of the large convective cluster near Tampa Bay.  Clean Window (10.3 µm) Infrared Imagery shows that offshore convection waned between 1100 and 1300 UTC, shifting to a location just south of Tampa.  (Click here for a slower animation)

GOES-16 Clean Window Infrared (10.33 µm) Imagery from 1102-1327 UTC on 31 July 2017 (Click to animate)

About an hour after Emily made landfall, a toggle between Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images, below, showed the compact cluster of deep convection — cloud-top infrared brightness temperatures were as cold as -74º C just off the Florida coast.

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images (Click to enlarge)

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images (Click to enlarge)

For more information on Emily, refer to the National Hurricane Center website, or to the CIMSS Tropical Weather Pages.

Aircraft dissipation trail in Iowa

July 28th, 2017 |

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

An aircraft “dissipation trail” formed over far southern Iowa during the late morning hours on 28 July 2017 — which was seen on GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61  µm) and Shortwave Infrared (3.9) µm) imagery (below).

GOES-16

GOES-16 “Red” Visible (0.64 µm, tpo), Near-Infrared “Snow/Ice” (1.61 µm, middle) and Shortwave Infrared (3.9) µm, bottom) images [click to play animation]

As explained in this blog post, these types of cloud features are caused by aircraft either ascending or descending through a cloud layer composed of supercooled water droplets. Cooling from wake turbulence (reference) — and/or the particles from the jet engine exhaust acting as ice condensation nuclei — then cause the small supercooled water droplets to change phase and transform into larger ice crystals (which often fall from the cloud layer, creating “fall streak holes“).

Therefore, the glaciated aircraft dissipation trail appears darker on the 1.61 µm “snow/ice” images (since ice is a strong absorber of radiation at that wavelength), and colder (brighter white) on the 3.9 µm shortwave infrared images.

1 week of Upper Midwest MCS activity: a GOES-16 overview

July 26th, 2017 |
GOES-16 Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 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 *

During the week of 19 July26 July 2017, the Upper Midwest was affected  by a number of strong to severe Mesoscale Convective System (MCS) events, as shown in an animation of GOES-16 “Clean” Infrared Window (10.3 µm) images (above).

At the beginning of that time period, a derecho moved across the region on 19 July producing widespread damaging winds, large hail and a few tornadoes (blog post).

Following the derecho, a separate outbreak of thunderstorms exhibited well-defined “enhanced-V” storm top signatures in western Wisconsin (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Another MCS produced tornadoes and damaging winds across eastern Iowa and northern Illinois on 21 July (SPC storm reports) — at one point a storm in northern Illinois exhibited a seldom-seen “warm trench” surrounding an overshooting top (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Early in the day on 23 July, “transverse banding” — a signature indicating the likelihood of high-altitude turbulence — was seen around the northern periphery of an MCS that was centered in southern Illinois (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

A pattern of mesoscale banding was displayed by thunderstorms that produced localized 1-2″ amounts of rainfall across southern Wisconsin on 26 July (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Also noteworthy was the swath of very heavy rainfall during this 1-week period across eastern Iowa, far southwestern Wisconsin and northern Illinois (below), which was responsible for flash flooding in those areas.

7-day total precipitation, departure from normal and percent of normal [click to enlarge]

7-day total precipitation, departure from normal and percent of normal [click to enlarge]

Tornado in Maryland

July 24th, 2017 |

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

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

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

An isolated thunderstorm that was moving eastward across Maryland just after Midnight on 24 July 2017 intensified as it crossed Chesapeake Bay, eventually producing a waterspout which moved onshore near Bay City (just southwest of Stevensville/Bay Bridge Airport, station identifier KW29) — this tornado was responsible for 1 injury and EF2-rated damage (NWS Mount Holly PNS  | SPC storm reports). GOES-16 “Clean” Infrared Window (10.3 µm) images (above; also available as a 23-Mbyte animated GIF) showed that there were 3 distinct “pulses” when cloud-top infrared brightness temperatures cooled to the -71 to -75º C range (lighter gray pixels embedded within dark black regions) before the storm produced the tornado at 0529 UTC. Since one of the default GOES-16 Mesoscale Sectors was providing coverage over the eastern US, imagery was available at 1-minute intervals.

A comparison of 1-minute GOES-16 vs 15-minute GOES-13 (GOES-East) Infrared Window images (below; also available as a 17-Mbyte animated GIF) provided a convincing demonstration of the value of more frequent image scan intervals for monitoring severe convection. The improved spatial resolution of GOES-16 Infrared imagery — 2 km at satellite sub-point, vs 4 km for GOES-13 — also allowed for a more accurate depiction of cloud-top IR brightness temperature patterns and values.

1-minute GOES-16 (10.3 µm, left) vs 15-minute GOES-13 (10.7 µm, right) Infrared Window images [click to play MP4 animation]

1-minute GOES-16 (10.3 µm, left) vs 15-minute GOES-13 (10.7 µm, right) Infrared Window images [click to play MP4 animation]