A comparison of Water Vapor images from GOES-17 (GOES-West) and GOES-15 Water Vapor images (above) showed the signature of an anomalously-deep closed low that was moving southeastward over the Beaufort Sea north of Alaska during the 11 June – 12 June 2019 period. The images are shown in the native projection of each satellite — GOES-17 is positioned over the Equator at 137.2º W longitude, while GOES-15 is located at 128º W. The improved GOES-17 spatial resolution (2 km at nadir, vs 4 km for GOES-15) and more frequent imaging (every 10 minutes, vs every 30 minutes for GOES-15) allowed for a better depiction of this cutoff low — including smaller-scale features near the center of the broad circulation.

GFS model 500 hPa geopotential height, wind, and standardized height anomaly (source) analyses at 6- hour intervals (below) indicated 500 hPa geopotential height anomaly values reached -3 to -4 sigma (lighter shade of violet) for this cutoff low.

View only this post Read Less

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) of severe thunderstorms (SPC storm reports) that developed across central Nebraska and northern Kansas along and ahead of an advancing frontal boundary (surface analyses) on 08 June 2019. Robust overshooting tops were very apparent with many of the storms, and a few Above-Anvil Cirrus Plumes were also seen.

The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images are shown below. Numerous overshooting tops exhibited infrared brightness temperatures in the -70 to -75ºC range; note the appearance of a wave feature which propagated radially outward from an overshooting top in south-central Nebraska after 0030 UTC.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) showed a fast-moving jet of marine layer stratus moving westward from the Seward-Chenega area into the far southern Cook Inlet in south-central Alaska on 08 June 2019. A narrow finger of the marine stratus penetrated farther inland across the lower elevations of Iliamna Lake (which is located between Pedro Bay and Kokhanok). Note that at 2245 UTC the GOES-17 Mesoscale Sector was shifted southward, to better monitor a Gulf of Alaska storm.

This inland intrusion of marine stratus was driven by the presence of a warm thermal trough across Interior and Southwest Alaska (surface analyses) — animations of 10-minute GOES-17 Full Disk visible imagery (below) included hourly plots of surface wind barbs and air temperature. Note that some sites farther inland across southwestern Alaska had temperatures in the upper 60s to low 70s F.

At Iliamna Airport — located along the northern edge of Lake Iliamna — southeasterly winds gusted to 22 knots at 01 and 03 UTC (below).

A similar type of thermally-driven phenomenon is sometimes observed in the San Francisco Bay area, as shown here and here.

View only this post Read Less

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the formation of a lake breeze along the western shore of Wisconsin — in the wake of a cold frontal passage — on 05 June 2019. This lake breeze enhanced surface convergence, which played a role in the formation of a thunderstorm that produced hail as large as 2.50 inches in diameter when a prominent overshooting top was evident (NWS Green Bay).

The lake breeze also caused sharp drops in surface air temperature — from low 80s to middle 50s F — along with fog reducing visibility to 0.5 mile or less at Milwaukee and Racine in southeastern Wisconsin (below). The arrival of lake breeze fog also restricted the visibility to 0.5 mile or less at Waukegan in northeastern Illinois.

View only this post Read Less