The remnants of Typhoon Hagibis in the Bering Sea

October 14th, 2019 |

GOES-17 Mid-level Water Vapor (6.9 µm) images with surface reports plotted in cyan, then contours of the PV1.5 pressure, followed by the GOES-17 Air Mass RGB [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images with surface reports plotted in cyan, then contours of PV1.5 pressure plotted in red, followed by Air Mass RGB images [click to play animation | MP4]

An animation sequence of GOES-17 (GOES-West) Mid-level Water Vapor (6.9 µm) images with surface reports, then contours of PV1.5 pressure, followed by Air Mass Red-Green-Blue (RGB) images (above) showed the remnants of Typhoon Hagibis in the southern Bering Sea on 14 October 2019. During this time period, the extratropical cyclone was analyzed as a Hurricane Force low (surface analyses) —  winds gusted to 62 knots at Adak (PADK) and 60 knots at Shemya (PASY). The PV1.5 surface represents the “dynamic tropopause”, which model fields depicted as  descending as low as the 700 hPa pressure level. Due to the markedly-lower tropopause around and west of the low center, those areas appeared as deeper hues of red/orange on the Air Mass RGB images (influenced by the higher concentrations of ozone-rich stratospheric air within the atmospheric column). The striping seen early in the animation was caused by GOES-17s ABI Loop Heat Pipe issue.

In rawinsonde data from St. Paul Island (PASN), the objectively-decoded tropopause descended from 226 hPa (11 km) at 12 UTC on 14 October to 336 hPa (8.1 km) at 00 UTC on 15 October (below).

Plots of rawinsonde data at St. Paul Island [click to enlarge]

Plots of rawinsonde data at St. Paul Island [click to enlarge]

On the following day, a toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2319 UTC on 15 October and 0100 UTC on 16 October (below) showed the remnants of Hagibis briefly making landfall southeast of Anadyr, Russia (UHMA) as a Gale Force low. Winds at Anadyr gusted to 54 knots shortly after the low moved inland.

Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2319 UTC on 15 October and 0100 UTC on 16 October [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2319 UTC on 15 October and 0100 UTC on 16 October [click to enlarge]

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. 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]

Note that this lightning-producing convection was occurring near the leading edge of the cyclone’s mid-tropospheric dry slot, as seen in GOES-16 Water Vapor imagery (below).

GOES-16 "Red" Visible (0.64 µm, left) and Mid-level Water Vapor (6.9 µm, right) images, with GLM Groups plotted in red [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, left) and Mid-level Water Vapor (6.9 µm, right) images, with GLM Groups plotted in red [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 from southwestern Ontario to 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, its circulation 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]

===== 17 October Update =====

Aqua MODIS True Color and False Color RGB images [click to enlarge]

Aqua MODIS True Color and False Color RGB images [click to enlarge]

After the area had already experienced its wettest Fall season on record, additional rainfall and snowmelt from this winter storm exacerbated ongoing flooding problems. A comparison of 250-meter resolution Aqua MODIS True Color and False Color Red-Green-Blue (RGB) images (source) centered over northeastern North Dakota (above) revealed flooding along the Red River (which flows northward along the North Dakota / Minnesota border) — water appears as darker shades of blue in the False Color image.

A Suomi NPP VIIRS Flood Product depicting floodwater fractions in the Red River Valley north of Grand Forks ND (as visualized using RealEarth) is shown below.

Suomi NPP VIIRS Flood Product, depicting floodwater fractions in the Red River Valley north of Grand Forks, ND [click to enlarge]

Suomi NPP VIIRS Flood Product, depicting floodwater fractions in the Red River Valley north of Grand Forks, ND [click to enlarge]

===== 18 October Update =====

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

On 18 October — 1 week after the height of the historic blizzard — GOES-16 Day Cloud Phase Distinction RGB images showed snow cover (brighter shades of green) remaining in areas that received the highest snowfall accumulations (such as Morden MB 32″; Vang ND 29″; Olga ND 28″; Langdon ND 27″).

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]

Super Typhoon Hagibis in the West Pacific Ocean

October 7th, 2019 |

Himawari-i8

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

JMA Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed the pinhole eye of Super Typhoon Hagibis as it rapidly intensified to a Category 5 storm (ADT | SATCON) by 12 UTC on 07 October 2019. Hagibis exhibited some trochoidal motion and variations in forward speed as it approached the Northern Mariana Islands, eventually moving just south of the small uninhabited island of Anatahan (north of Saipan, station identifier PGSN) around 15 UTC.

A toggle between VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (below) showed the eye just west of Anatahan.

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (credit: William Straka, CIMSS) [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP (credit: William Straka, CIMSS) [click to enlarge]

During the period 06 October/2014 UTC to 07 October/0714 UTC, Himawari-8 “Red” Visible (0.64 µm) images (below) showed the initial period of rapid intensification, during which Hagibis developed a well-defined pinhole eye.

Himawari-8 "Red" Visible (0.64 µm) images [click to play animation | MP4]

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

Hagibis was moving over warm West Pacific water with high values of Sea Surface Temperature and Ocean Heat Content — the storm was also moving through an environment characterized by low deep-layer wind shear.

===== 08 October Update =====

Himawari-8 "Clean" Infrared Window (10.4 µm) images [click to play animation | MP4]

Himawari-8 “Clean” Infrared Window (10.4 µm) images [click to play animation | MP4]

2.5-minute rapid scan Himawari-8 Infrared images (above) showed Hagibis during an eyewall replacement cycle (erosion of the small inner eye, with the subsequent formation of a larger-diameter eye). The small inner eyewall could be seen rotating within the larger eye as this transition was taking place. Once the eyewall replacement cycle was completed, Hagibis re-intensified to a Category 5 storm at 18 UTC.

VIIRS Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 (below) displayed the eye and eyewall region of the Category 4 storm.

VIIRS Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 (courtesy of William Straka, CIMSS) [click to enlarge]

A toggle between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1556 UTC (below) provided a nighttime view of Hagibis.

VIIRS Day/Night Band (0.7 µm ) and Infrared Window (11.45 µm) images at 1556 UTC [click to enlarge]

VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1556 UTC (courtesy of William Straka, CIMSS) [click to enlarge]