NASA Global Hawk flight path, with Cloud Height, Tropical Overshooting Tops, and Lightning data (click to play animation)

The NASA Global Hawk aircraft are once again being used to study tropical cyclones during the 2014 season. As part of CIMSS participation in GOES-R Proving Ground activities, a Global Hawk flight path tool was developed to display important parameters such as ACHA Cloud Top Height, Tropical Overshooting Tops, and lightning (above; click image to play animation). Global Hawk pilots use this product to navigate the aircraft around locations of potential turbulence.

GOES-13 0.63 µm visible channel images (click to play animation)

To support the Global Hawk investigation of Tropical Storm Dolly on 02 September 2014, the GOES-13 satellite was placed into Rapid Scan Operations (RSO) mode to provide images at 5-7 minute intervals. GOES-13 0.63 µm visible channel images (above; click to play animation) and 10.7 µm IR channel images (below; click to play animation) are shown which cover the 3-hour period of the Global Hawk flight segment shown above. There is evidence of overshooting tops seen in the visible imagery, with cloud-top IR brightness temperatures of -80º C and colder (purple color enhancement).

GOES-13 10.7 µm IR channel images (click to play animation)

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Suomi NPP VIIRS Day Night Band (0.70 µm) image (click to enlarge)

Tropical Storm Dolly has formed in the western Gulf of Mexico. The Suomi NPP VIIRS Day Night Band imagery, above, shows the exposed low-level swirl of the storm (then still a tropical depression). North-northwesterly shear (shown here, from this site) means the deep convection (shown below) is displaced to the east of south of the the low-level circulation (click here for a toggle between the Day Night Band and the 11.45µm imagery). Cloud-top IR brightness temperatures from VIIRS were as cold as -87º C. ASCAT winds from 0230 UTC show a region of tropical storm-force winds associated with convection east and north of the circulation center.

Suomi NPP VIIRS Infrared (11.45 µm) image (click to enlarge)

Early-morning visible imagery from GOES-13, below, shows the large area of convection over the southern Gulf. The NHC-reported positions of the storm at 0900 UTC and 1500 UTC (22.6º N, 94.8º W and 23.4º N, 96.5º, respectively) are indicated by the red boxes on the images. Strong convection just south of the surface circulation developed at sunrise, obscuring the low-level swirl. That strong convection is especially apparent in the GOES-13 10.7 imagery, at bottom. GOES IR Brightness Temperatures were as cold as -84º C in the animation. (For more on Dolly from the National Hurricane Center, see this link).

GOES-13 Visible Imagery (0.63 µm) (click to animate)

GOES-13 Infrared Imagery (10.7 µm) (click to animate)

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Global composite of IR images, with tropical cyclone center points (click to play Animated GIF)

It is rather rare to have no named tropical cyclones anywhere on the globe on the first day of September, but that was the case on 01 September 2014. A sequence of hourly global composite IR images from the SSEC RealEarth web map server (Animated GIF | MP4 movie file | YouTube video) showed the void of tropical activity — until Tropical Depression 5 formed late in the day in the Gulf of Mexico. This feature later became Tropical Storm Dolly early on 02 September.

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Meteosat-10 Saharan Air Layer product (click to play animation)

The CIMSS Saharan Air Layer (SAL) product (above; click image to play animation) showed a large pocket of SAL (yellow to red color enhancement) drifting westward over the far western Atlantic Ocean and toward the Gulf of Mexico on 28 August 2014.

On GOES-13 0.63 µm visible channel images (below; click image to play animation), the hazy signature of the SAL dust could be seen surging westward, not far to the south of Category 1 intensity Hurricane Cristobal.

GOES-13 0.63 µm visible channel images (click to play animation)

The SAL also exhibited a warm/dry signature (yellow to orange color enhancement) on the corresponding GOES-13 6.5 µm water vapor channel images (below; click image to play animation).

GOES-13 6.5 µm water vapor channel images (click to play animation)

At 17:16 UTC, a Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from the SSEC RealEarth web map server (below) showed that Hurricane Cristobal had developed an eye formation.

Suomi NPP VIIRS true-color image

A comparison of AWIPS-2 images of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel data (below) revealed that the coldest cloud-top IR brightness temperatures (-77º C, lighter gray color enhancement) were located within convection just southwest and southeast of the eye.

Suomi NPP VIIRS 0.64 µm visible image and 11.45 µm IR channel image

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