Comparing NUCAPS temperature values to forecast fields

November 29th, 2020 |

Gridded NUCAPS estimates of 850-mb Temperature, 1851 UTC on 30 November 2020 (Click to enlarge)

Late November is a time when cold outbreaks can pass over relatively warm Great Lakes waters (click here for recent observations) and produce lake-effect snow. Gridded NUCAPS observations derived from NOAA-20 CrIS and ATMS data, above, shows a large area with temperatures colder than -12ºC over northwest Ontario and northern Minnesota, just upwind of the Great Lakes;  Lake Superior’s surface temperature at the time was around 5ºC —  a temperature difference that support lake-effect precipitation.  How well do the NUCAPS observations compare to model predictions of the environment?

Forecasts from the 1200 UTC run of the NAM, below, valid at 1800 UTC, and from the 1500 UTC run of the Rapid Refresh, valid at 1900 UTC, show -12ºC in bright magenta.  (Model analyses taken from this website)  NUCAPS analyses suggest the cold air is moving south faster than anticipated by the model.

 

6-h forecast of 850-mb Temperature, valid 1800 UTC on 29 November 2020 (Click to enlarge)

4-hour forecast of 850-mb temperature from the Rapid Refresh, valid 1900 UTC on 29 November 2020 (Click to enlarge)

This site can be used to view gridded NUCAPS fields outside of AWIPS.  The 850-mb analysis from the pass is shown below.  It’s important to recall that Gridded NUCAPS fields include data from all retrieved profiles — including profiles for which the infrared retrieval failed (usually in locations with thick clouds, and those from which the infrared and microwave retrievals both failed (usually in locations with rain). This mapping for the temperature gridding below shows where infrared retrievals failed (yellow) and where infrared and microwave retrievals both failed (red).

850-mb Temperature fields, 1849 UTC on 29 November 2020 (Click to enlarge)

The ‘yellow’ points north and west of the Great Lakes were associated with clouds that are apparent in this VIIRS True Color image, taken from the UW-Madison Direct Broadcast ftp site (Link). The clouds were associated with a departing low pressure system (link).

NOAA-20 VIIRS True-Color imagery, 1850 UTC on 29 November 2020 (Click to enlarge)

Mesoscale bands of snowfall in New Mexico, Oklahoma and Texas

November 29th, 2020 |

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

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

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed a cutoff low that was moving slowly eastward across eastern New Mexico and the Oklahoma/Texas Panhandle on 28 November – 29 November 2020. This system was helping to produce rain and snow across parts of that region — and some elongated convective elements were evident across the OK/TX Panhandles. Snowfall totals included 2.5 inches in New Mexico and 3.0 inches in Texas, with 4.8 inches at Felt, Oklahoma (NOHRSC).

On the following day, a few north-to-south oriented mesoscale bands of snow cover were evident on GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below). Since snow is a strong absorber of radiation at the 1.61 µm wavelength, it appeared as darker shades of black on those images. Swaths of lighter snow cover melted rather quickly during the day.

GOES-16 "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

Eruption of the Lewotolok volcano in Indonesia

November 29th, 2020 |

Himawari-8 True Color RGB images [click to play animation | MP4]

Himawari-8 True Color RGB images [click to play animation | MP4]

JMA Himawari-8 True Color Red-Green-Blue (RGB) images created using Geo2Grid (above) showed the volcanic clouds produced by an eruption of Lewotolok in Indonesia on 29 November 2020 — with one cloud plume moving to the northwest, and another moving more rapidly southeastward. This difference in volcanic cloud propagation was due to directional wind shear, as revealed by rawinsonde data from Kupang on the island of Timor (below), located about 250 km southeast of Lewotolok. A shift to northwesterly winds occurred at an altitude around 9 km (the 322 hPa pressure level).

Plot of rawinsonde data from Kupang, Indonesia [click to enlarge]

Plot of rawinsonde data from Kupang, Indonesia [click to enlarge]

Himawari-8 Ash RGB images [click to play animation | MP4]

Himawari-8 Ash RGB images [click to play animation | MP4]

Himawari-8 Ash RGB images (above) displayed an ash signature for both volcanic plumes, which became more diffuse after about 5 hours. Himawari-8 retrievals of Ash Height from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) showed maximum values in the 16-18 km range for the southeast-moving cloud (the  advisory issued by the Darwin VAAC listed maximum height values of 50,000 feet or 15 km).

Himawari-8 retrievals of Ash Height [click to enlarge]

Himawari-8 retrievals of Ash Height [click to enlarge]


Great Lakes water temperatures in late November

November 29th, 2020 |

ACSPO SSTs from VIIRS on NOAA-20, 28 November (1728 and 1911 UTC) and 29 November (0727 UTC). Click to enlarge

Clear skies over most of the five Great Lakes on 28-29 November allowed the VIIRS instrument on NOAA-20 to gather information for Advanced Clear-Sky Processing for Ocean (ACSPO) Sea Surface Temperatures.  The animation above shows two afternoon images (from 28 November 2020, at 1728 UTC and 1911 UTC) and one morning image (from 29 November 2020 at 0727 UTC).  The color enhancement shows values from 35ºF to 55ºF.

Lake Erie shows the warmest temperatures, just over 50ºF in the eastern part of the Lake. High Pressure over the Ohio River valley on 28 November (2100 UTC analysis) meant light winds over Lake Erie. The lack of wind-induced mixing allowed for warming (a few degrees F between 1728 and 1911 UTC) of the surface skin of the lake. Lake Superior shows temperatures around 40º F (albeit a bit warmer along just off the Upper Peninsula of Michigan); Lakes Michigan and Huron, western Lake Michigan and northwest Lake Ontario show temperatures in the mid-40s. Eastern Lake Ontario shows temperatures in the upper-40s.


Note: You can compare these observations to previous years here, for Lake Michigan. (Links to comparisons at other lakes are at that link as well). Thanks to the Blog Reader for this link!