GOES-12 IR images

GOES-12 IR images from the CIMSS Tropical Cyclones site (above) showed that Tropical Storm Bill began to exhibit a well-defined curved banding structure during the early  daytime hours  on 16 August 200. In addition, the IR imagery displayed the formation of  a large convective burst near the center of the circulation.

GOES-12 IR image + deep layer mean winds

The CIMSS deep layer mean winds product overlaid on a GOES-12 IR image (above) as well as an animation of GOES-12 water vapor images (below) indicated that there was a large subtropical ridge of high pressure in place to the north of Bill, which would act to keep the storm moving on a west-northwesterly path for several days.

GOES-12 water vapor images + model forecast tracks

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GOES-12 visible images

GOES-12 visible images from the CIMSS Tropical Cyclones site on 15 August 2009 (above) showed that the low-level circulation of Tropical Storm Ana (the first named Atlantic Basin tropical storm of the 2009 season) had become exposed from the main area of deep convection located farther to the east. This suggested that  Ana was moving into a region of increasing westerly wind shear, though the CIMSS deep layer wind shear product (below) only showed about 5-10 knots of  shear over the tropical cyclone at that time.

GOES-12 IR images + deep layer wind shear product

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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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