GOES-13 10.7 µm IR images

Hurricane Danielle went through another period of intensification on 26 August 2010, and GOES-13 10.7 µm IR images (above) and 0.63 µm visible images (below) from the CIMSS Tropical Cyclones site revealed the formation of a well-defined eye that was not obscured by a Central Dense Overcast (CDO) as was the case in previous days.

GOES-13 0.63 µm visible images

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GOES-13 10.7 µm IR imagery

Tropical Storm Earl formed in the eastern Atlantic Ocean on 25 August 2010. GOES-13 10.7 µm IR images from the CIMSS Tropical Cyclones site (above) revealed a well-defined circulation, with the development of convective clusters and curved bands.

The environment around Earl was one that exhibited low values of 200-850 hPa deep layer wind shear (below), which was favorable for further intensification of the tropical cyclone.

GOES-13 IR image + 200-850 hPa Deep Layer Wind Shear product

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Visible and infrared GOES-11 imagery over the eastern Pacific Ocean have indicated a persistent southwestward-moving cloud edge during the past several days. The visible image, above, from 1830 UTC on 25 August, shows a distinct cloud edge arcing from northwest to southeast. What is the history of this feature? The visible imagery loop below, showing 1800 UTC images over the course of 4 days, show that the feature likely has its roots in dry air exiting the North American continent. A loop of 11-micron imagery from GOES-11 every two hours (here) shows the steady progression of the feature, and the persistent sharpness of the edge. Brightness temperatures of the clouds are steady near 287-288 K; brightness temperatures in the clear region are 290-291 K.

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GOES-15 Super Rapid Scan Operations (SRSO) 0.63 µm visible images

As part of its NOAA post Launch Science Test, the GOES-15 satellite was placed into Super Rapid Scan Operations (SRSO) mode on 24 August 2010, providing images at 1-minute intervals to monitor Hurricane Danielle. McIDAS images of GOES-15 0.63 µm visible channel data (above) did show some interesting convective development associated with Danielle, but no eye was apparent.

While Danielle had intensified into a Category 2 hurricane during the preceding overnight hours, a collapse in both intensity and in satellite appearance began during the daylight hours. AWIPS images of the CIMSS MIMIC Total Precipitable Water (TPW) product (below) did show that some dry air became entrained into the southern and eastern quadrants of Danielle, but fairly far from the center of the tropical cyclone.

MIMIC Total Precipitable Water (TPW) product

In addition to the entrainment of dry air, there was also a change from light easterly wind shear on 23 August to light northwesterly wind shear on 24 August, as seen on images from the CIMSS Tropical Cyclones site (below). It is unclear to what degree either of these factors played in the decrease in intensity  of Hurricane Danielle (which was actually downgraded to a Tropical Storm later in the day)..

GOES-15 IR image with Deep Layer Shear overlay + 85 GHz microwave image + MIMIC TPW

There was an 8-hour gap in SRSO imagery due to a GOES-15 satellite maneuver, but once the 1-minute interval imagery resumed, it almost appeared as though Danielle was trying to form a more organized convective eyewall later during the day (below).

GOES-15 Super Rapid Scan Operations (SRSO) 0.63 µm visible images

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