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]

Shear vortices over the Great Lakes and Ohio River Valley

June 7th, 2017 |

GOES-16 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play animation]

GOES-16 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play animation]

A well-defined train of wind shear vortices was revealed on GOES-16 Water Vapor images — Upper-level (6.2 µm), Mid-level (6.9 µm) and Lower-level (7.3 µm) — propagating westward over the Great Lakes on 07 June 2017 (above).

A larger-scale view using Mid-level 6.9 µm images (below) showed additional (and larger) vortices which were moving eastward over the Ohio River Valley. Pilot reports of turbulence are plotted on the water vapor images, and many of those reports appeared to be in the general vicinity of the vortices.

GOES-16 Water Vapor (6.9 µm) images [click to play animation]

GOES-16 Water Vapor (6.9 µm) images [click to play animation]

A 3-hour-interval Mid-Level Wind Shear product derived from GOES-13 (GOES-East) atmospheric motion vectors (AMVs) is shown below. An elongated cyclonic shear axis was present from the Northeast US to the Ohio River Valley, and the location of the water vapor vortices appeared to correspond to the wind shear gradients along the northern and southern edges of this axis.

GOES-13 Mid-Level Wind Shear product [click to enlarge]

GOES-13 Mid-Level Wind Shear product [click to enlarge]

Blowing Dust over northern Montana

May 24th, 2017 |

GOES-16 Visible Imagery (0.64 µm) from 1707 through 1802 UTC on 24 May 2017 (Click to enlarge)

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

The strong pressure gradient around a Low Pressure system over Alberta and Saskatchewan caused strong winds across northern Montana on 24 May 2017, and blowing dust was the result, especially in Hill and Blaine Counties. The visible animation, above, from 1707 to 1802 UTC on 24 May, shows a faint hazy signature along the border of Canada.  The emphasis is on the word ‘faint’ — it is very difficult to pick out the signature unless you know it’s there already  (Thanks to MIC Tanja Fransen at WFO Glasgow for alerting us to this event).  The ‘Blue’ Visible band animation (below) similarly shows the dust, but it is not distinct in this band either.  (*Note* — part of this, of course, is because the default enhancement for visible imagery has been used.  If the ‘low light’ enhancement is applied, the dust signature is more apparent. This visible animation from 1502-2122, courtesy Tanja Fransen, more obviously shows the dust).

GOES-16 Visible Imagery (0.47 µm) from 1707 through 1802 UTC on 24 May 2017 (Click to enlarge)

Brightness Temperature Difference products are routinely available in AWIPS. The Split-Window Difference (SWD), below, shows the difference between the ‘Clean Infrared Window’ (10.33 µm) and the ‘Dirty Infrared Window’ (12.3 µm) (‘Clean’ and ‘Dirty’ referring to a little and more, respectively, water vapor absorption) has historically been used to detect dust: dust will absorb 10.33 µm radiation but it will not absorb 12.3 µm radiation, thus the SWD can highlight regions of dust.  However, that difference is also influenced by water vapor above the dust, and by the type of dust being lofted.

Split Window Difference (10.33 µm – 12.2 µm) from 1707 to 1802 UTC, 24 May 2017 (Click to enlarge)

The Cloud Phase Difference (8.5 µm – 11.2 µm) also can highlight regions of dust, and for this case the signal of dust was a bit more distinct.

Cloud Phase Brightness Temperature Difference (8.5 µm – 11.2 µm) from 1707 to 1802 UTC, 24 May 2017 (Click to enlarge)

Surface data plotted over the 0.64 µm at 1712 UTC, below, show the strong winds in the region (Here is an image at 1802 UTC). Visibilities in the areas of blowing dust were reported to be near zero.

GOES-16 Visible (0.64 µm) at 1712 UTC and 1700 UTC surface observations (Click to enlarge)

A Terra MODIS true-color Red/Green/Blue (RGB) image at 1745 UTC, below, revealed that the source of some of the most dense dust plumes appeared to be uncultivated fields located north and northeast of Havre.

Terra MODIS true-color RGB image (Click to enlarge)

Terra MODIS true-color RGB image (Click to enlarge)

(Added: Stuart Lawrence, south of Rosetown in west-central Saskatchewan, tweeted out this video that showed the dust storm there. He reported winds up to 98 km/hour). Here is another image of the dust in Saskatchewan.

The GOES Aerosol/Smoke Products (GASP) showed a noticeable signal for this dust. Here is a large-scale animation from 1315-2145 UTC, with a closer view from 1015-2345 UTC here)

Tornadoes and large hail in Minnesota and Wisconsin

May 16th, 2017 |

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in cyan [click to play animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in cyan [click to play animation]

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

A significant outbreak of severe thunderstorms developed on 16 May 2017, producing damaging winds, large hail and tornadoes from Texas to Wisconsin (SPC storm reports). On the northern end of this outbreak, hail as large as 3.0 inches in diameter fell in northwestern Wisconsin, and a long-track tornado resulted in 1 fatality and 25 injuries near Chetek (NWS Twin Cities MN summary). GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images (above) showed the development of the convective systems; surface-to-cloud-top parallax-corrected SPC storm reports are plotted on the images. Overshooting tops and above-anvil cloud plumes were evident on the visible images, with well-defined “enhanced-V” and “cold/warm thermal couplet” storm top signatures seen on the infrared imagery.

A closer view of the GOES-16 Visible and Infrared Window images (below) provided more detail of the supercell storm-top structure. Note that the pronounced infrared enhanced-V signature began to develop near the Minnesota/Wisconsin border just before 2100 UTC, which was about 40 minutes prior to the first Wisconsin hail report of 2.5 inches and the beginning of the long-track tornado. Since the early 1980s (reference), the enhanced-V satellite signature has been recognized as a reliable predictor of supercell thunderstorms having a high potential to produce either damaging winds, large hail or tornadoes; an automated Enhanced-V / Overshooting Top product (reference) will be available using the ABI instrument on the GOES-R series of satellites..

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports and hourly surface reports [click to play animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports and hourly surface reports [click to play animation]

A comparison of GOES-13 (GOES-East) and GOES-16 Infrared Window images (below) demonstrated the advantage of improved spatial resolution (2-km at satellite sub-point with GOES-16, vs 4-km with GOES-13) for identifying features such as cold overshooting tops.

Infrared Window images from GOES-13 (10.7 µm, top) and GOES-16 (10.3 µm, bottom) , with SPC storm reports plotted in cyan [click to play animation]

Infrared Window images from GOES-13 (10.7 µm, top) and GOES-16 (10.3 µm, bottom) , with SPC storm reports plotted in cyan [click to play animation]

True-color Red/Green/Blue (RGB) imagery (below; courtesy of Kaba Bah, CIMSS) offered another view of the storms on a regional scale.

GOES-16 true-color RGB images [click to play animation]

GOES-16 true-color RGB images [click to play animation]

A time series of the the NOAA/CIMSS ProbTor product and its ingredients, below, showed large values of ProbTor (forced especially, perhaps, by large values of Azimuthal Shear).  Storm Reports from SPC show a tornado time near Chetek of 2235 UTC

Time Series of NOAA/CIMSS ProbTor (Red Line) and ProbTor ingredients from 2034 UTC 16 May through 0146 UTC 17 May 2017 (Click to enlarge)

An animation of NOAA/CIMSS ProbSevere, below, from 2100 through 2310 UTC, shows the radar-defined objects, including an annotated one that was associated with the Chetek tornado (for which the time series is displayed above).  That object crosses the St. Croix River from Minnesota into Wisconsin at 2100 UTC, subsequently moving over Turtle Lake and Barron, and ending up, at 2310 UTC (the end of the animation) near Ladysmith.  It was the sole radar object with a ProbTor that exceeded 20% — with one exception.  At 2220 and 2230 UTC the radar object just to the west of the Chetek tornado radar object had ProbTor values of 20% and 26%, respectively. (Click here for an unannotated animation).

NOAA/CIMSS ProbSevere from 2100 through 2310 UTC on 16 May 2017 (Click the enlarge)