GOES-12 10.7 µm IR images

AWIPS images of the GOES-12 10.7 µm IR channel (above) showed a strong Mesoscale Convective System (MCS) that developed over  South Dakota on 13 August 2009. This MCS spawned a long-lived Mesoscale Convective Vortex (MCV)  — sometimes referred to as a Mesocale Vorticity Center or MVC — that later helped to initiate another MCS over Minnesota and Wisconsin during the pre-dawn hours on 14 August 2009.

GOES-12 visible images

The circulation of the MCV then continued to move northeastward across the Upper Peninsula of Michigan during the day on 14 August, as seen on an animation of GOES-12 visible images (above) and radar reflectivity (below).

Radar reflectivity

The Blended Total Precipitable Water (TPW) product (below) showed that there was a plume of higher moisture (TPW values of 37-41 mm or 1.5 to 1.6 inches) feeding northeastward across Wisconsin into the Upper Peninsula, helping to sustain convective development in the vicinity of the MCV.

Blended TPW product + GOES-12 IR images

Since the Atlantic Basin has been seemingly disinterested in producing any notable tropical cyclone activity so far this season, one had to look to the Upper Midwest region of the US for signs of any “tropical development”:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
500 PM EDT FRI AUG 14 2009

.SYNOPSIS...

TO THE S...LAZY FLOW EXISTS ACROSS THE UPPER MISSISSIPPI VALLEY AND
GREAT LAKES. AS A RESULT...MESOSCALE VORTICITY CENTER GENERATED BY
CONVECTION IN SD TWO NIGHTS AGO AND NOW LOCATED OVER CNTRL UPPER MI
IS STILL JUST DRIFTING ALONG IN AN ERLY DIRECTION. MVC CIRCULATION
REMAINS VERYWELL-DEFINED...JUST AS IMPRESSIVE AS IT WAS 24HRS AGO
DUE TO THE VERY LIGHT MID/UPPER FLOW IN WHICH IT IS EMBEDDED. WEAK
FLOW HASKEPT IT FROM SHEARING APART. IF THIS WAS LOCATED IN THE TROPICS...
YOU WOULD THINK IT WAS A TROPICAL SYSTEM. ALTHOUGH COMPACT...TIGHT
SPIRALING CLOUD CANOPY AROUND MVC HAS BEEN SUFFICIENT TO LIMIT AFTN
HEATING...SO CONVECTIVE DEVELOPMENT HAS BEEN KEPT IN CHECK THIS AFTN.

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MODIS true color and false color images

A comparison of MODIS “true color” and “false color” Red/Green/Blue (RGB) images (above) showed that significant amounts of ice remained in parts of southern Hudson Bay and northern James Bay in Canada on 10 August 2009. On the true color RGB image (using MODIS bands 01/04/03), the ice did not appear as as bright as the surrounding clouds, and had a slightly “light blue” appearance. On the  false color RGB image (using MODIS bands 02/07/07), the ice (along with clouds that were composed of ice crystals) exhibited a darker red appearance, in contrast to the cyan to white colored supercooled water droplet clouds.

Also note the hazy appearance over parts of Ontario, just to the west of James Bay: this was due to smoke aloft from recent fire activity in Alaska and the Yukon Territory.

A map of the departure from normal ice concentration (below, courtesy of the Canadian Ice Service) indicated that there were large areas where the ice  was in the 7/10ths to 10/10ths range above the normal concentration for the date (darker blue colors). The persistence of a deep area of low pressure just south of Hudson Bay (July 2009 mean 850 hPa geopotential height) kept that region (along with much of the eastern US) unusually cold during the summer, which undoubtedly slowed the rate of ice melt in Hudson Bay and James Bay.

Ice Concentration (departure from normal)

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MODIS true color and MODIS false color images

250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site (above) showed a large smoke plume and “fire hot spot” from the 4700-acre “Narraguinnep Fire” that was burning in southwestern Colorado on 08 August 2009. On the false color image, the fire hot spot appears as a large cluster of pink to red  pixels.

The MODIS true color image viewed using Google Earth (below) shows that the fire was located in the far western portion of the Uncompahgre National Forest, about midway between Dove Creek and Dolores in southwestern Colorado. The fire was believed  to have been started by lightning on the previous day.

MODIS true color image (viewed using Google Earth)

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GOES-12 water vapor images

GOES-12 water vapor images (with aircraft location)

Continental Flight 128, en route from Rio de Janiero to Houston on 3 August, encountered severe turbulence over the Atlantic Ocean just north of Hispaniola, according to AP Press reports. Other press reports suggest the turbulence occurred southeast of Puerto Rico (see this one from Bloomberg, for example), but flight tracking software available online shows a flight path that changed north of Hispaniola, presumably in response to the turbulence encountered. The aircraft landed in Miami at 5:30 EDT, or 0930 UTC; according to press reports, the turbulence was encountered an hour before that, or around 0830 UTC. [UPDATE: on-board flight logs (courtesy of John Williams at RAP at NCAR) suggest the flight path change, presumably right after the encounter with turbulence, occurred around 0800 UTC; that data has been superimposed on GOES-12 Imager water vapor (shown above) and window channel imagery (linked below)] What was happening in the satellite imagery at the time?

MIMIC Total Precipitable water shows that the region of turbulence was moistening with time as a tropical wave approached from the east. However, GOES-12 satellite data show only modest convection in the region. For example, the 6.7 micron water vapor imagery from 08:02 UTC shows only scattered convection, although the presence of developing deep convection very near the location of the turbulence to the north of Hispaniola suggests a strong correlation. A loop of the water vapor imagery certainly suggests the presence of a leading edge to the convective development, which leading edge is very close to the region of severe turbulence. Perhaps the two are related, but at first glance this case demonstrates the challenges inherent in predicting damaging turbulence.

(Update on 10 August: two McIDAS-V image loops, courtesy of Joleen Feltz at CIMSS, show the flight position plotted on Water Vapor (6.5 micron) imagery and window channel (10.7 micrometers) imagery derived from GOES-12 Imager data, clearly showing the flight deviation just as the plane flies over deepening new convection just to the north of Hispaniola.)

Cloud-top cooling (below) estimated using the UW/CIMSS Convective Initiation algorithm indicate cooling of 13 K in 15 minutes. Assuming a moist adiabatic atmosphere with a lapse rate of 6.5 K/km, this is vertical growth of 2 km in 15 minutes, equivalent to upward motion exceeding 200 cm per second. The flight data (the dashed line in the figure below) suggest that the airplane flew very close to this developing cumulus tower.

GOES-12 instantaneous cloud top cooling rate (with aircraft flight path)

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