GOES-13 0.63 µm visible images (color enhanced)

We received the following in an email from Dan St. Jean at the NWS forecast office in Gray/Portland Maine, who also supplied us with an animation of color-enhanced GOES-13 0.63 µm visible images (above) from 26 May 2010:

A backdoor cold front was moving southwestward down the Maine coast, while some significant convection (at the start of the loop) was moving southward along the extreme eastern coast of Maine. It's hard to say why and exactly where, but the activity appeared to throw a gravity wave ahead of it moving just ahead of the cold front. Anyway I thought you might find this worth a closer look as we rarely see these crisp wave features up here.

The visible images reveal the closely-spaced packet of wave clouds that marked the southwestward propagation of the gravity wave or “undular bore” — thanks for the heads-up on this interesting feature Dan!

Another view of the wave clouds can be seen on a Red/Green/Blue (RGB) false color image using NOAA-15 AVHRR channels 01/02/04 (below). In this particular RGB image combination, low clouds have more of a yellow tint, while colder, higher-topped clouds appear brighter white.

NOAA-15 AVHRR false color RGB image (using channels 01/02/04)

An AWIPS image of the MODIS Sea Surface Temperature (SST) product (below) showed that the initial convective outflow boundary likely moved over an area of cooler offshore waters (SST values generally in the middle 40s to lower 50s F, blue to cyan colors) — with a stronger marine boundary layer inversion over the colder waters, the gravity wave / undular bore feature might have been able to become more well-defined as it was ducted toward the southwest.

MODIS Sea Surface Temperature (SST) product

View only this post Read Less

POES AVHRR Sea Surface Temperatre (SST) product

During 24 May – 25 May 2010, a northward flux of unseasonably warm (daily high temperatures in the 80s and 90s F) and humid (dew points in the middle 60s to low 70s F) air moved northward across the Great Lakes region. However, an AWIPS image of the POES AVHRR Sea Surface Temperature (SST) product (above) showed that SST values were still in the upper 30s to low 40s F over much of Lake Superior and the upper 40s to low 50s F over much of Lake Michigan.

The cold water temperatures caused the surface air to cool to saturation, with widespread advection fog developing over a great deal of Lake Superior and Lake Michigan. A 250-meter resolution MODIS Red/Green/Blue (RGB) image created using Bands 1/4/3 (below) revealed an interesting pattern of “shock waves” in the lake fog as the southeasterly flow was interacting with the coastline of parts of eastern Wisconsin.

MODIS true color RGB image (created using Bands 1/4/3)

During the subsequent overnight hours, a comparison of the 4-km resolution GOES-13 fog/stratus product with the corresponding 1-km resolution MODIS fog/stratus product (below) demonstrated how the improvement in spatial resolution was an aid to more accurately locating the exact boundaries of the fog over western Lake Superior and the inland areas in the vicinity of Duluth, Minnesota (station identifier KDLH).

4km resolution GOES-13 fog/stratus product + 1-km resolution MODIS fog/stratus product

With arrival of daylight on the morning of 25 May, an animation of GOES-13 0.63 µm visible channel images (below) showed how the lake fog features were affecting various inland portions of northeastern Minnesota at different times.

GOES-13 0.63 µm visible channel images

View only this post Read Less

MODIS true color (Bands 1/4/3) and false color (Bands 7/2/1) RGB images

A comparison of 250-meter resolution MODIS Red/Green/Blue (RGB) true color (using Bands 1/4/3) and false color (using Bands 7/2/1) images from the SSEC MODIS Today site (above) showed the main portion of the surface oil slick in the northern Gulf of Mexico on 24 May 2010. This was Day 34 following the deadly explosion on the offshore oil rig Deepwater Horizon, and the damaged underwater wellhead continued to discharge more than 5,000 barrels of oil per day.

A day later, MODIS true color and false color images from 25 May 2010 (below) continued to exhibit a distinct signature of the surface oil slick.

MODIS true color (using Bands 1/4/3) and false color (using bands 7/2/1) images

View only this post Read Less

GOES-13 visible images + lower-tropospheric atmospheric motion vectors

An animation of GOES-13 visible images from the CIMSS Tropical Cyclones site (above) showed the development of a discrete low-level cyclonic circulation associated with the first Atlantic Basin tropical cyclone “Invest” of the season on 23 May 2010. An overlay of lower-tropospheric atmospheric motion vectors (along with a handful of ship reports) also showed a broad cyclonic circulation around this developing cloud feature.

GOES-13 IR images (below) showed that there were some large clusters of cold-topped convection located off to the northeast, but this deep convection did not appear to be directly related to the developing low-level cyclonic circulation seen on visible imagery.

GOES-13 IR images

GOES-13 water vapor imagery with an overlay of deep layer (850-200 hPa) wind shear (below) showed 2 factors present that were unfavorable for the rapid intensification of Invest 90L: very dry air aloft moving in from the west, along with increasing values of wind shear — however, model guidance suggested that there was a small chance that this system could eventually develop into a subtropical cyclone.

GOES-13 water vapor images + deep layer wind shear

View only this post Read Less