Rain/hail swath in Nebraska and Kansas

June 26th, 2017 |

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

As indicated in the Tweet above from NWS Hastings, GOES-16 imagery highlighted the presence of a narrow swath of rainfall and hail in the wake of a small thunderstorm that moved south/southeastward across the Nebraska/Kansas state line area on 26 June 2017.

A 3-panel comparison of GOES-16 Visible (0.64 µm), Snow/Ice (1.61  µm) and Shortwave Infrared (3.9  µm) images (below) revealed a subtle signature of the hail swath on the Snow/Ice images (where ice features appear as darker shades of gray: southern NE  | northern KS), while the Shortwave Infrared images showed that the hail and rainfall swathaccumulations in southern Kansas included 0.58″ at Clay Center and 0.49″ at Hebron — remained slightly cooler (lighter gray) as the adjacent dry land surfaces continued to warm during the early to middle afternoon hours. SPC storm reports listed hail of 1.75 inches in diameter in southern Nebraska and 1.25 inches in northern Kansas.

GOES-16 Visible (0.64 µm, left), Snow/Ice (1.61 µm, center) and Shortwave Infrared (3.9 µm, right) images, with hourly surface reports plotted in yellow and SPC storm reports of hail size plotted in red [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left), Snow/Ice (1.61 µm, center) and Shortwave Infrared (3.9 µm, right) images, with hourly surface reports plotted in yellow and SPC storm reports of hail size plotted in red [click to play MP4 animation]

Regarding the cooling seen associated with the rainfall/hail swath, a Land Surface Temperature (LST) product derived using Aqua MODIS data (below) indicated that LST values were generally in the upper 60s to upper 70s F within the narrow swath,  in contrast to LST values in the 90s to around 100º F adjacent to the swath.

Aqua MODIS Land Surface Temperature product, Visible (0.65 µm), Infrared Window (11.0 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]

Aqua MODIS Land Surface Temperature product, Visible (0.65 µm), Infrared Window (11.0 µm) and Shortwave Infrared (3.7 µm) images [click to enlarge]

Tropical Storm Cindy

June 24th, 2017 |

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

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

As Tropical  Storm Bret was forming off the coast of South America, Potential Tropical Cyclone 3 (PTC3) was becoming more organized as it moved from the western Caribbean Sea across the Yucatan Peninsula of Mexico and into the Gulf of Mexico on 19 June 2017 (MIMIC TPW). On 20 June, one of the GOES-16 Mesoscale Sectors was positioned  over PTC3 and  provided 1-minute imagery — Visible  (0.64 µm)  and  Infrared Window (10.3  µm) images (above) showed deep convective bursts moving northward to reveal an exposed Low Level Circulation Center (LLCC).

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

Early in the day on 21 June, 1-minute GOES-16 Visible and Infrared Window images (above) showed multiple LLCC features associated with PTC3, with deep convection remaining well to the north/northwest. In addition, Mid-level Water Vapor (6.9  µm) images (below) indicated that a large amount of dry air had wrapped into the southern and eastern portions of the storm circulation.

GOES-16 Visible (0.64 µm, left) and Water Vapor (6..9 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Water Vapor (6..9 µm, right) images [click to play MP4 animation]

However, by mid-day a more consolidated central circulation had developed, as seen on Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images (below) — and PTC3 was upgraded to Tropical Storm Cindy.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with surface pressure plotted in yellow and station identifiers plotted in cyan [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with surface pressure plotted in yellow and station identifiers plotted in cyan [click to enlarge]

Hourly images of the MIMIC Total Precipitable Water product covering the 19-24 June period (below) showed  the northward transport of rich tropical moisture into the Gulf  Coast states, which then moved northeastward toward the Northeast US bringing heavy rainfall and flooding to many locations (WPC storm summary).

MIMIC Total Precipitable Water [click to play animation]

MIMIC Total Precipitable Water [click to play animation]

Maps of daily rainfall during the 21-24 June period (along with 7-day rainfall totals, departure from normal and percent of normal) are shown below.

21-24 June daily precipitation, along with 7-day Precipitation Total, 7-day Departure from Normal and 7-day Percent of Normal [click to enlarge]

21-24 June daily precipitation, along with 7-day Precipitation Total, 7-day Departure from Normal and 7-day Percent of Normal [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).

Scattering and Shadows

June 19th, 2017 |

GOES-16 Imagery over New England from 1022 through 1117 UTC on 19 June 2017. Blue Band (0.47 µm), upper left; Red Band (0.64 µm), upper right; ‘Veggie’ Band (0.86 µm), lower left; ‘Snow/Ice’ Band (1.61 µm), lower right. Click to enlarge.

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

The animation of GOES-16 imagery, above, showing, clockwise from upper left, the GOES-16 0.47 µm, 0.64 µm, 1.61 µm and 0.86 µm channels, shows lows clouds over southeast New England, with a few mid-level clouds aloft. The moving mid-level clouds are casting shadows on the lower clouds beneath. Note that the shadows appear darkest at the longest wavelength. This is shown in the AWIPS cursor readout below as well — for the point selected, the 1.61 µm reflectance is 5.4%, and it increases to 18.9% at 0.47 µm. Why does it change by wavelength?

AWIPS read-out of reflectance in a shadow east of Cape Cod. Note the reflectance increases as wavelength decreases. (Click to enlarge)

Rayleigh scattering in the atmosphere is a function of wavelength: scattering is more effective at shorter wavelengths. Thus, the atmosphere is scattering the greatest amount of 0.47 µm radiation (compared to the longer wavelengths shown here). Shadows are darker (there is less detected reflectance) at longer wavelengths because less longer-wavelength radiation is scattered towards the satellite sensor.

The tweet from the National Weather Service in Melbourne, below, shows another shadow scene with 0.86 µm imagery.