Early-season winter storm in the Northern Plains

October 12th, 2019 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface weather type plotted in red [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface weather type plotted in red [click to play animation | MP4]

With the approach of an anomalously-deep 500 hPa low, an early-season winter storm produced very heavy snowfall and blizzard conditions across the Northern Plains — particularly in central/eastern North Dakota and southern Manitoba — during the 10 October12 October 2019 period. GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the long duration of precipitation across that region. Text listings of snowfall totals and wind gusts are available from WPC, NWS Bismarck and NWS Grand Forks (more complete storm summaries: NWS Bismarck | NWS Grand Forks). The highest storm total snowfall amount in far southern Manitoba was 32 inches south of Morten (which reported a snow depth of 30 inches on the morning of 12 October), with 30 inches in central North Dakota at Harvey.

GOES-16 “Red” Visible (0.64 µm) images (below) displayed the storm during the daylight hours on 10/11/12 October.

GOES-16 "Red" Visible (0.64 µm) images on 10/11/12 October, with hourly precipitation type plotted in red [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images on 10/11/12 October, with hourly precipitation type plotted in red [click to play animation | MP4]

On 11 October, GOES-16 Visible images with an overlay of GLM Flash Extent Density (below) revealed intermittent clusters of lightning activity over northwestern Minnesota, northeastern North Dakota and southern Manitoba — while no surface stations explicitly reported a thunderstorm, NWS Grand Forks received calls from the public about thundersnow. The texture of cloud tops in the Visible imagery also supported the presence of embedded convective elements, which likely enhanced snowfall rates as they pivoted across that area (note that this convection was occurring along the leading edge of the mid-tropospheric dry slot seen in the Water Vapor imagery above). An animation of GOES-16 Visible imagery with plots of GLM Groups and surface weather type is available here.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of GLM Flash Extent Density [click to play animation | MP4]

One important aspect of this storm was the formation of a trough of warm air aloft or trowal (SHyMet | Martin, 1998) as the surface low began to enter its occluded phase on 11 October — contours of Equivalent Potential Temperature along the 295 K isentropic surface (below) helped to diagnose the axis of the trowal as it curved cyclonically across southwestern Ontario, southern Manitoba and then southward over North Dakota.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with 295 K equivalent potential temperature contours plotted in yellow and surface fronts plotted in red [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with 295 K Equivalent Potential Temperature contours plotted in yellow and surface fronts plotted in red [click to play animation | MP4]

A similar animation with contours of 295 K specific humidity (below) also displayed the orientation of a west-to-east cross section B-B’ (green) across northern Northern Minnesota and northern Minnesota.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with 295 K Specific Humidity contours plotted in yellow and surface fronts plotted in red [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with 295 K Specific Humidity contours plotted in yellow and surface fronts plotted in red [click to play animation | MP4]

The Line B-B’ cross section at 16 UTC (with and without contours of Equivalent Potential Temperature) is shown below. Note the deep column of upward vertical velocity (highlighted by color shading of Omega) centered over Langdon, North Dakota — the moist trowal airstream can be seen sloping isentropically upward and westward behind the 3 g/kg Specific Humidity contour, as it approached the region of upward vertical motion. Langdon received 27 inches of snowfall; the prolonged southward passage of the trowal over North Dakota likely contributed to this accumulation.

Cross section of RAP40 model fields along Line B-B' at 16 UTC [click to enlarge]

Cross section of RAP40 model fields along Line B-B’ at 16 UTC [click to enlarge]

As the storm was gradually winding down on 12 October, it exhibited a very broad middle-tropospheric signature on GOES-16 Water Vapor imagery (below).

GOES-16 Mid-level Water Vapor (6.9 µm) images, with surface frontal positions [click to play animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with surface frontal positions [click to play animation | MP4]

Typhoon Hagibis south of Japan

October 11th, 2019 |

Himawari-8 Clean Window Infrared (10.41 µm) imagery every 2.5 minutes, from 1429 UTC to 1932 UTC on 11 October 2019. Imagery courtesy JMA (Click to animate)

Himawari-8 Advanced Himawari Imagery (AHI) from the ‘Target’ sector, above, show a strong albeit asymmetric storm south of Ise Bay and southwest of Tokyo Bay. Clean window infrared (10.41 µm) imagery, above, shows a compact eye that is cooling with time, suggesting weakening (and/or becoming more cloud-filled). Most of the cold clouds in the storm are north of the center, a distribution that suggests shear.  However, the storm is still producing strong convection that is wrapping around the eye. By the end of the animation, at 1929 UTC, the eye is no longer distinct.  This toggle compares the 1432 and 1929 UTC images.  A decrease in storm cloud-top organization near the eye is apparent.

Data from the CIMSS Tropical Page at 1530 UTC on 11 October, shown below in a stepped animation, show southerly shear that will increase with time over the storm as it moves towards Japan. Microwave imagery (85 GHz) also suggest a sheared storm, as does the infrared imagery.  Low-level water vapor imagery (7.3 µm), here), shows dry air (yellows in the color enhancement chosen) prevalent over the southern half of the storm.  These data suggest that a slow extratropical transition is underway.

Past and Predicted path of Hagibis, Observed Shear at 1500 UTC, the latest 85 GHz image over the storm, and Infrared window imagery at 1530 UTC. (Click to enlarge) All imagery from the CIMSS Tropical Page.

The Airmass RGB image over the Pacific Basin, (animation), (from this site at CIRA) also shows dry air consistent with a transition from tropical to extratropical. The zoomed-in image of the Airmass RGB, below, from Real Earth, shows the dry air as shades or orange/copper southwest of the storm, in contrast to the deep tropical moisture, feeding into the storm from the south, that is greener.

Airmass RGB from Himawari-8 Data, 1630 UTC on 11 October 2019

The Joint Typhoon Warning Center has the latest on Hagibis. A projected path valid at 1500 UTC 11 October is here.

Suomi NPP overflew Hagibis at 1639 UTC on 11 October. The toggle below shows the Day Night Band (0.7 µm Visible imagery) and the 11.45 µm infrared imagery from the Visible Infrared Imaging Radiometer Suite (VIIRS) Instrument.  A larger-scale view of the Day Night Band is here.  (Imagery courtesy William Straka, CIMSS)

Suomi NPP Day Night Band Visible Imagery (0.7 µm) and Window Infrared (11.45 µm) from VIIRS, 1638 UTC on 11 October 2019 (Click to enlarge)

High Plains leeside cold frontal gravity wave

October 10th, 2019 |

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with plots of surface wind barbs and gusts in knots [click to play animation | MP4]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with plots of surface wind barbs and gusts in knots [click to play animation | MP4]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed the classic signature of a leeside cold frontal gravity wave (reference) moving southward across the High Plains on 10 October 2019. Peak wind gusts of 50-60 mph were reported at some sites in eastern Colorado and western Kansas — and impressive drops in surface air temperature accompanied the cold frontal passage.


On the corresponding GOES-16 “Red” Visible (0.64 µm) imagery (below), note the lack of clouds along the western end of the cold front (across the New Mexico / Texas border region).

GOES-16 "Red" Visible (0.64 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images, with plots of surface wind barbs and gusts in knots [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images, with plots of surface wind barbs and gusts in knots [click to play animation | MP4]

A plot of rawinsonde data from Amarillo, Texas at 12 UTC (below) showed how shallow the cold air was behind the cold front as it first moved southward through the Texas Panhandle.

Plot of rawinsonde data from Amarillo, Texas [click to enlarge]

Plot of 12 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

However, note that GOES-16 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Amarillo (below) indicated that peak contributions were in the middle troposphere — in the 440-500 hPa pressure range — with no surface radiation contributions at 6.9 µm or 6.2 µm. It was the deep-tropospheric nature of the leeside cold frontal gravity wave that allowed its signature to be sensed by the 6.9 µm and 6.2 µm Water Vapor spectral bands.

GOES-16 Water Vapor weighting functions, calculated using 12 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

GOES-16 Water Vapor weighting functions, calculated using 12 UTC rawinsonde data from Amarillo, Texas [click to enlarge]

ACSPO SSTs from VIIRS in AWIPS

October 10th, 2019 |

ACSPO SSTs (range from 41 F to 68 F or 5 C to 20 C) at 0818 UTC on 10 October 2019 (Click to enlarge)

SSEC/CIMSS is producing Advanced Clear Sky Processor for Ocean ACSPO Sea Surface Temperatures (SSTs) from Direct Broadcast data received in Madison. (Here is a blog post on ACSPO SSTs in Guam) The example above shows Great Lakes water temperatures around 0800 UTC on 10 October 2019. The example below shows SSTs computed from the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi-NPP and NOAA-20 around Vancouver Island from 8 through 10 October (a period when the Pacific Northwest was enjoying a spate of clear skies that are necessary for ACSPO SST computation).  These data are available via LDM feed.

ACSPO SSTs (range from 41 F to 68 F or 5 C to 20 C) from 8 October through 10 October 2019 (Click to enlarge)