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 significant snow cover (brighter shades of green) remaining in parts of northeastern North Dakota and southern Manitoba that received the highest storm total snowfall accumulations (for example, 32″ south of Morden MB, 29″ at Vang ND, 28″ at Olga ND and 27″ at Langdon ND). The site south of Morden MB reported a residual snow depth of 10 inches that morning.

The probability of “intense convection” using geostationary satellite data

September 27th, 2019 |

Researchers from NOAA and UW-CIMSS have developed an experimental model that predicts the “probability of intense convection” inferred from GOES ABI and GLM fields. The model is a convolutional neural network, which carries the assumption that the inputs are images and have spatial context. It is a great tool for image classification.

GOES-16 ABI CH02 reflectance (a visible channel), ABI CH13 brightness temperature (an infrared window channel [IR]), and GLM flash extent density (FED; generated using glmtools),  were used as inputs to the model. The model learned important features that have been traditionally difficult or expensive to code into an algorithm, such as pronounced overshooting tops (OTs), enhanced-V features, thermal couplets, above-anvil cirrus plumes (AACPs), strong brightness temperature gradients, cloud-top divergence, and texture from visible reflectance.

It is hoped that such a model may be able to one day:

  • provide earlier notice of developing or decaying intense convection
  • provide guidance in regions with no weather radars
  • provide a quantitative way to leverage 1-min mesoscale scans
  • ultimately improve the accuracy and lead time of severe weather warnings

The model is very experimental and is not yet running in real-time. The remainder of this post catalogues some examples of the deployed model on select scenes.

The movies below use as a background the CH02-CH13 “sandwich” product, whereby cloud-top 11-µm brightness temperature and 0.64-µm reflectance can be seen in tandem. This generally helps observers see how changes in storm-top structure correlate with changes in 11-µm brightness temperature. A grid of “probability of intense convection” was generated for each scene with a moving 32×32 pixel window (each pixel = ~2 km), with the model generating one probability for each window. These probabilities were then contoured with the 25%, 50%, and 90% contours as blue, cyan, and magenta. Preliminary severe local storm reports from the SPC rough log are also plotted as circles.

The example below shows that the model handled two separate severe wind threats in Missouri, identifying cold cloud top regions in the IR that also looked “bubbly” from the visible channel. As the sun was setting, a cold front lit up with very intense convection from Oklahoma through Missouri. Again, the model did a decent job highlighting the strongest areas of convection which correlated well with severe local storm reports. It should also be noted that the model does not seem to have significantly degraded output when the visible channel is missing (after sunset).

 

The next example is at a higher satellite viewing angle in western Nebraska, western South Dakota, and eastern Wyoming. The model again does a good job highlighting the strongest areas of storms. It should be noted that not every identified region has severe reports and not every severe report has a probability of intense convection ? 25%, but that there is generally good correspondence between reports and the model probabilities nonetheless.

 

This example is from the Southeast U.S. in more of a low-shear “microburst” environment instead of a high-shear “supercell” environment. You can see that instead of predicting high probabilities for all of the convective storms, the model exhibits the highest probabilities for the storm clusters that at least subjectively look the strongest.

 

This next example from the Central Plains demonstrates the ability to discern decaying convection, as the first storm moves into Missouri and then quickly diminishes in appearance and in probability. It also demonstrates the model’s ability to pick out multiple threat areas within a large cloud mass at night.

 

This is an example using mesoscale scans. Despite not being trained with 1-min data, the model predictions still look very fluid and reasonable. This could be an excellent way for scientists and forecasters to leverage 1-min observations in a quantitative manner.

 

Another example using GOES-East 1-min mesoscale scans. The model generally picks out the strongest portions of a MCS in Illinois and Indiana.

 

At a very high viewing angle, the model predicts probabilities of ?90% for a storm in Arizona. The storm did not generate severe reports, but was warned on by the NWS multiple times.

 

The model is deployed during an early autumn severe weather outbreak.

This example shows the model deployed on 1-min mesoscale scans over very intense thunderstorms in Argentina. It demonstrates that the model is generally applicable to anywhere in the world where advanced imager and GLM-like observations are present.

 

Here, a model was trained without GLM data and deployed for an example in the Alaska Panhandle, where GLM data is not available. This storm prompted a severe thunderstorm warning from the Juneau, AK NWS office. Note the change in the values of the probability contours. The maximum probability for this storm was 36% at 02:43 UTC. In a relative sense, the intense convection probability product could still be useful in unconventional regions, such as Alaska.

Hurricane Dorian reaches Category 5 intensity

September 1st, 2019 |

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Overlapping 1-minute Mesoscale Domain Sectors provided GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 30-second intervals (above) as Hurricane Dorian reached Category 5 intensity just east of Great Abaco Island in the Bahamas during the morning hours on 01 September 2019. West of Dorian, station Identifier MYGF is Freeport on Grand Bahama Island (which stopped reporting at 00 UTC on 01 September, due to evacuation).

As noted in the 15 UTC NHC discussion, the eye of Dorian was exhibiting a pronounced “stadium effect”, with a smaller-diameter surface eye sloping outward with increasing altitude (below).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 1200 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 1200 UTC [click to enlarge]

GOES-16 Visible images with and without overlays of GLM Flash Extent Density (below) revealed that lightning activity began to ramp up within the eyewall region after 12 UTC.

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

A Mid-Level Wind Shear product (below) showed that Dorian had been moving through an environment of low shear — generally 10 knots or less — during the 00-15 UTC time period on 01 September.

Mid-layer Wind Shear product, 00-15 UTC [click to enlarge]

Mid-layer Wind Shear product, 00-15 UTC [click to enlarge]


As pointed out by NWS Grand Forks (above), portions of the outer cays just east of Great Abaco Island could be seen in GOES-16 Visible imagery through breaks in the low-level clouds within the eye (below).

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth are shown below, as the eye was moving over Great Abaco Island.

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

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


After moving slowly westward across Great Abaco Island, Dorian later became the first Category 5 hurricane on record to make landfall on Grand Bahama Island (below). Station identifier MYGF is Grand Bahama International Airport in Freeport, and MYGW is West End Airport.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

===== 02 September Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Prior to sunrise on 02 September, 1-minute GOES-16 Infrared images (above) showed Dorian moving very slowly — with a forward speed of only 1 mph — across the eastern end of Grand Bahama Island (as it remained at Category 5 intensity).

After sunrise, 1-minute GOES-16 Visible and Infrared images (below) showed that the eye of Dorian was finally beginning to move very slowly northwestward away from Grand Bahama Island. At the end of the animation (15 UTC), Dorian was downgraded slightly to a high-end Category 4 hurricane.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Suomi NPP VIIRS True Color RGB and Infrared images (below) provided a view of Dorian at 1817 UTC.

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

At 21 UTC, a comparison of MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images (below) suggested that a tongue of drier air from the northwest and west was wrapping into the southern and southeastern portion of Dorian’s circulation.

MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images at 21 UTC [click to enlarge]

MIMIC Total Precipitable Water and DMSP-16 SSMIS Microwave images at 21 UTC [click to enlarge]

A long animation of GOES-16 Infrared images (below) covers the 1.5-day period from 1200 UTC on 01 September to 2359 UTC on 02 September — and initially includes 30-second images from 1200-1515 UTC on 01 September. Dorian was rated at Category 5 intensity from 1200 UTC on 01 September until 1400 UTC on 02 September. Station identifier MYGF is Grand Bahama International Airport in Freeport.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]


Additional satellite imagery and products are available from EUMETSAT.

Hurricane Dorian

August 28th, 2019 |

NOAA-20 Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, courtesy of William Straka (CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, courtesy of William Straka (CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above) showed cold overshooting tops (darker black infrared enhancement) over the Leeward Islands as well as subtle mesospheric airglow waves propagating southward away from the center of Tropical Storm Dorian at 0606 UTC on 28 August 2019.

In a toggle between GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) and DMSP-18 SSMIS Microwave (85 GHz) images from the CIMSS Tropical Cyclones site (below), the Microwave image revealed a convective band that was wrapping around the northern portion of the center of Dorian at 0930 UTC.

GOES-16 "Clean" Infrared Window <em>(10.35 µm)</em> and DMSP-18 SSMIS Microwave <em>(85 GHz)</em> images [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [click to enlarge]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (below) also showed a convective burst wrapping around the eastern and northern edges of the center of Dorian after 15 UTC. The coldest cloud-top infrared brightness temperature associated with that early convective burst was -83ºC.

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Dorian was upgraded to a Category 1 Hurricane at 18 UTC. Prior to that time, the tropical cyclone had been moving through an environment of low deep-layer wind shear (below), one factor that is favorable for intensification. Dorian was also passing over water possessing warm sea surface temperatures and modest ocean heat content.

http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2019/08/.gifGOES-16 Infrared Window (10.35 µm) images, with contours of deep-layer wind shear at 19 UTC [click to enlarge]

GOES-16 Infrared Window (10.35 µm) images, with contours of deep-layer wind shear at 19 UTC [click to enlarge]

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth are shown below, from around the time when Dorian was upgraded from a Tropical Storm to a Hurricane.

VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

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

A comparison of GOES-16 Infrared (at 2330 UTC) and GMI Microwave (at 2341 UTC) images (below) revealed Dorian’s small eye.

GOES-16 Infrared (10.35 µm) and GMI Microwave (85 GHz) images [click to enlarge]

GOES-16 Infrared (10.35 µm) and GMI Microwave (85 GHz) images [click to enlarge]

===== 29 August Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

On 29 August, 1-minute GOES-16 Visible and Infrared images (above) showed that periodic convective bursts persisted around the center of Category 1 Hurricane Dorian.

During one of those convective bursts from 1800-1900 UTC, an increase in GOES-16 GLM Flash Extent Density was evident (below).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 Visible and Infrared images at 1852 UTC with and without an overlay of GLM Flash Extent Density are shown below. At that particular time, the overshooting top infrared brightness temperature reached a minimum value of -82.5C.

GOES-16 “Red” Visible (0.64 µm) image at 1853 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) image at 1852 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) image at 1853 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) image at 1852 UTC, with and without an overlay of GLM Flash Extent Density [click to enlarge]

===== 30 August Update =====

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

The eye of Dorian became more well-defined in 1-minute GOES-16 Visible and Infrared images (above) during the morning hours on 30 August.

A DMSP-17 Microwave (85 GHz) Microwave image at 1141 UTC (below) did not yet show a completely closed eyewall structure at that earlier time.

DMSP-17 SSMIS Microwave (85 GHz) Microwave image [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) Microwave image [click to enlarge]

Dorian was upgraded to a Category 3 hurricane at 18 UTC — the storm was moving into a narrow corridor of weaker deep-layer wind shear around that time. During the 3 hours leading up to 18 UTC, animations of 1-minute GOES-16 Visible and Infrared imagery — with and without an overlay of GLM Flash Extent Density — are shown below.

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images, with and without overlays of GLM Flash Extent Density [click to play animation | MP4]

===== 31 August Update =====

30-second GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

30-second GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

Overlapping 1-minute GOES-16 Mesoscale Domain Sectors provided imagery at 30-second intervals — Visible and Infrared animations of the Category 4 hurricane from 1430-1900 UTC are shown above and below, respectively. A longer Visible animation from 1100-2259 UTC is available here (courtesy of Pete Pokrandt, AOS).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

30-second GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]