Severe weather across southeastern Idaho

May 31st, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with plots of SPC storm reports [click to play MP4 animation]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed thunderstorms which produced hail, damaging winds and tornadoes (SPC storm reports) across southeastern Idaho on 31 May 2018. Note that after 2102 UTC a pronounced “enhanced-v” infrared storm top signature was exhibited by the larger supercell which produced most of the severe weather. The SPC storm reports on the imagery are “parallax-corrected”, such that they are plotted at a location matching the corresponding cloud-top features (applying the 10-km tropopause height from the 00 UTC Boise rawinsonde report).

As a surface cold front was moving through Idaho, large-scale forcing for ascent was increasing across the region within the middle troposphere as an upper-level trough moved eastward over California and Nevada — and strong southwesterly flow ahead of this trough was evident over eastern Idaho on GOES-16 Low-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, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play MP4 animation]

GOES-16 Lower-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play MP4 animation]



Suomi NPP and NOAA-20 view Tropical Depression Alberto over the lower Ohio River Valley

May 30th, 2018 |

Day Night Band Visible (0.7 µm) Imagery from Suomi NPP (0722) and NOAA-20 (0812 UTC) over Tropical Depression Alberto (Click to enlarge)

Suomi-NPP and NOAA-20 overflew tropical depression Alberto, at 0722 and 0812 UTC, respectively (orbit paths from this site), on 30 May 2018, and the near-Full moon provided ample illumination for the Day Night Band imagery, shown above.  A motion to the northeast is apparent.  Convection developed far to the north of the storm as well, south of Chicago, and a streak of lightning occurs over Oklahoma in the later image.  (For individual Day Night Band images in the loop, click here for Suomi NPP and here for NOAA-20) A similar loop, below, shows the Window Channel (11.45 µm) from the VIIRS instrument on Suomi NPP and NOAA-20. A tip of the Hat to Will Straka, CIMSS, for the imagery.

VIIRS Window Channel (I05) Infrared (11.45 µm) Imagery from Suomi NPP (0722) and NOAA-20 (0812 UTC) over Tropical Depression Alberto (Click to enlarge)

Added: NOAA-20 was declared Operational on 30 May 2018. Welcome NOAA-20!

Subtropical Storm Alberto gradually intensifies

May 27th, 2018 |

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0731 UTC or 3:31 am local time (above; courtesy of William Straka, CIMSS) showed Subtropical Storm Alberto when it was centered off the southwest coast of Florida on 27 May 2018. Note that NOAA-20 imagery is still considered preliminary and non-operational.

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below) revealed that dry air was wrapping into the circulation of Alberto during the day.

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” infrared Window (10.3 µm) images (below) showed that the low-level circulation center of Alberto became partially exposed, and the areal coverage and intensity of deep convection diminished somewhat during the day as the dry air was being entrained into the storm.

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of ship and buoy reports [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with hourly plots of ship and buoy reports [click to play MP4 animation]

===== 29 May Update =====

Composite of GOES-16 1-minute Mesoscale Domain Sector “Clean” Infrared Window (10.3 µm) images for the period 1630 UTC on 26 May to 1000 UTC on 29 May 2018 [click to play YouTube video]

A composite of GOES-16 1-minute Mesoscale Domain Sector “Clean” Infrared Window (10.3 µm) images for the period 1630 UTC on 26 May to 1000 UTC on 29 May 2018 (above; courtesy of Pete Pokrandt, AOS) showed Subtropical Storm Alberto as it moved northward across the Gulf of Mexico and eventually inland over Alabama.

 

Alberto

May 25th, 2018 |

GOES-16 ABI Band 10 (7.34 µm, low-level water vapor) Infrared imagery, 0822-1632 UTC on 25 May 2018 (Click to animate)

The National Hurricane Center has assigned the name ‘Alberto’ to region of low pressure that has persisted near the northwest Caribbean Sea for the past week. The low-level water vapor (7.34 µm) animation, above, shows abundant mid-tropospheric moisture to the east of the system. Dryer mid-level conditions are apparent west of Alberto: the storm structure is very asymmetric. Sheared systems such as this one typically do not strengthen quickly.

A plot of shear (from this site), below, shows Alberto in a region of westerly shear, with a forecast path towards a region that currently has higher shear — part of which is outflow. However, forecast models suggest the shear along the forecast path will decrease with time.  Sea-surface temperatures are warm enough to support tropical cyclones, and the forecast path is towards warmer waters.

Shear Analysis and Satellite imagery at 1500 UTC on 25 May 2018 (Click to enlarge)

Visible imagery, below, shows one low-level circulation center (others may be masked by the convection to the east) that is south and west of the main convection over the Caribbean.

GOES-16 ABI Visible (0.64 µm) Imagery, 1137-1642 UTC on 25 May 2018 (Click to animate)

Suomi-NPP overflew this region at 0723 UTC, and a toggle between the Window Channel Infrared (11.45 µm) and the Day Night Band Visible (0.70 µm) imagery (courtesy William Straka) is shown below. The low-level circulation is apparent in the Day Night Band to the west of the deep convection over the northwest Caribbean.

Suomi-NPP VIIRS Infrared (11.45 µm) and Day Night Band Visible (0.70 µm) Imagery at 0735 UTC on 25 May 2018 (Click to enlarge)

Total Precipitable Water, 1600 UTC on 24 May 2018 to 15 UTC on 25 May 2018 (Click to enlarge)

A MIMIC Total Precipitable Water animation, above, shows abundant moisture over the northwest Caribbean. As Alberto lifts to the north, that moisture will shift north as well, and flooding rains are possible over the southeastern United States. Flood Watches have been raised over Louisiana, Mississippi, Alabama and Georgia (below, from this site).

Hazards at 1700 UTC on 25 May 2018 (Click to enlarge)

The Geostationary Lightning Mapper (GLM) on GOES-16 observed lightning in the deep convection to the east of the system center. GLM is overlain on both infrared (top) and visible (bottom) imagery below (animations courtesy Dave Santek, CIMSS). The updating infrared animations are available here. GLM data for this system can also be viewed in RealEarth.

GOES-16 Infrared (10.3 µm) Imagery over Alberto at 5-minute time-steps, 1747 – 1832 UTC,  along with GLM observations of group density plotted every minute (See legend in image for times of GLM plots) (Click to enlarge)

GOES-16 Visible (0.64 µm) Imagery over Alberto at 5-minute time-steps, 1747 – 1832 UTC, along with GLM observations of group density plotted every minute (See legend in image for times of GLM plots) (Click to enlarge)

Updates on this system are sent every six hours from the National Hurricane Center. You can find more information there, or at the CIMSS Tropical Weather Website.