MIMIC Total Precipitable Water (click image to play animation)

The fifth named storm of the Atlantic Tropical season, Emily, is moving towards Hispaniola. The animation of MIMIC Total Precipitable Water (TPW), above, derived from microwave data, shows that Emily is embedded within a region of enhanced moisture (Hurricane Eugene in the eastern Pacific Ocean is also obvious within the TPW loop).

NOAA-18 10.8-micrometer imagery

Morning IR satellite imagery from NOAA-16 and NOAA-18 (above) shows a well-developed central dense overcast (CDO), with some overshooting tops. NOAA-18 recorded cloud-top brightness temperatures as cold as -84 C at 0630 UTC. The NOAA-16 visible image from 1149 UTC also shows overshooting tops.

Emily at 1345 UTC on 3 August (click image to play animation)

Emily is in an environment favorable for slow strengthening. Shear values are modest, oceanic heat content is high and Dry Air is at present displaced from the convection. The projected path over the high terrain of Hispaniola, however, should limit strengthening (and yield very heavy rains over that island).

There have been 5 other tropical systems named Emily in the Atlantic: in 1981, 1987, 1993, 1999 and 2005. The path of 1987’s Emily is — so far — closest to the path of 2011’s Emily. (Historical Hurricane paths are from the Unisys Hurricane page here)

For more information on Emily, version 2011, including its projected path off the east coast of the United States, please see the National Hurricane Center’s website and the CIMSS Tropical Cyclones website.

(Added, later on August 3rd:

GOES-15 visible imagery (click image to play animation)

Persistent shear has displaced the circulation from the convection, as shown in the loop above. Convection continues to develop in the center of the storm, but it does not persist there).

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

The GOES-R Proving Ground requested that the GOES-13 satellite be placed into Super Rapid Scan Operations (SRSO) mode to monitor the development of Tropical Storm Don as it approached the far southern coast of Texas on 29 July 2011:

Subject: Administrative, GOES-13 (GOES-East) SRSO scheduled for July 29

*Topic*: GOES-13 (GOES-East) SRSO is scheduled for: July 29, 2011

*Correction*: *Product(s) or Data Impacted:* GOES-13 (GOES-East)
Imager Data and Products

*Date/Time Issued*: July 29, 2011 1705 UTC

*Product(s) or Data Impacted:* GOES-13 (GOES-West) Imager Data and
Products

*Date/Time of Initial Impact*: July 29, 2011 J/date 210 1815 UTC

*Date/Time of Expected End*: July 29, 2011 J/date 211 0115 UTC

*Length of Event*: 7 hours

*Impacts on Users and Significance*: Smaller PACUS frame with shortened Southern Hemisphere scan (Southern Hemisphere scan hourly). Increased frequency of images over area of interest (see Details)

*User Actions*: None.

*Details/Specifics of Change*: GOES-R Proving Grounds Testing Over Tropical Storm Don in the Gulf of Mexico at 27 North and 96 West

*Requestor: *CIRA

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation; also available as a QuickTime movie) showed a number of convective bursts associated with the tropical storm — note that there were several periods where images were available at 1-minute intervals while GOES-13 was in SRSO mode. The ABI instrument on GOES-R will actually be able to provide images as frequently as every 30 seconds over special regions of interest (such as tropical cyclones or severe thunderstorms).

A sequence of three AWIPS images of 1-km resolution MODIS and POES AVHRR IR data (below) displayed intricate cloud top structures and very cold cloud top IR brightness temperatures — as cold as -90ºC (darker violet color enhancement) on the 14:23 UTC MODIS image and the 20:21 UTC POES AVHRR image.

MODIS 11.0 µm and POES AVHRR 10.8 µm IR images

For the three individual 1-km resolution MODIS and POES AVHRR IR images above, comparisons with the corresponding 4-km resolution GOES-13 IR images are shown below. There are slight time differences between the MODIS/AVHRR IR and the GOES-13 IR images — but the majority of the northwestward shift in the location of features on the GOES images is due to parallax.

Even though the spatial resolution of the IR channels on the ABI instrument on GOES-R will be 2-km, these 1-km resolution comparisons still serve to demonstrate that improved spatial resolution should allow better detection of such detailed cloud top structures and cold cloud top IR brightness temperatures associated with tropical cyclones.

08:09 UTC MODIS 11.0 µm IR and 08:15 UTC GOES-13 10.7 µm IR images

14:23 UTC POES AVHRR 10.8 µm IR image and 14:32 UTC GOES-13 10.7 µm IR image

20:21 UTC POES AVHRR 10.8 µm IR image and 20:30 UTC GOES-13 10.7 µm IR image

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MIMIC TPW

Microwave estimates of total precipitable water (from the CIMSS MIMIC website), above, from 24-27 July 2011, show the progression of a tropical wave through the northwest Caribbean Sea into the southern Gulf of Mexico. Late in the day on 27 July, Air Force Reconaissance found a closed circulation with winds that were strong enough to earn the system a tropical storm designation.

GOES 15 Visible Image 2245 UTC 27 July

Visible imagery from late in the day (above) on the 27th shows extensive convection, with some overshooting tops over the Yucatan Channel and over the adjacent landmass. Forecasts are for Don to strengthen slowly as it moves towards the west-northwest. Oceanic heat content estimates from RSMAS as displayed at the CIMSS Tropical Weather website show a region of high heat content (associated with the Loop Current in the Gulf of Mexico) north of the projected path of Don. Intensification of Don could be more rapid if the storm moves farther to the north, over the region of higher heat content.

Shear values around Don are low. That and the warm sea surface temperatures over the Gulf argue for slow intensification.

Don’s projected path into south Texas takes it to a region suffering from extreme drought, as shown here.

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GOES 15/GOES 13 Sounder loop

The earth-viewing instruments on the GOES-15 spacecraft, which is above 90 W longitude, were turned on July 25th, and will be sending Imager and Sounder data for the next two weeks. Satellites in storage are periodically awakened to test functionality. GOES-West, currently GOES-11, will be retired at the end of the year and GOES-15 is a candidate to replace that Geostationary Satellite at 135 W Longitude.

The above loop shows Sounder data from GOES-15 and GOES-13, both remapped to the same projection, for 1746 UTC on July 27th. Note that the most bands of the Sounder imagery from GOES-15 shows cleaner signals; colder detectors onboard GOES-15 (because GOES-15 has a different configuration than GOES-13) mean that the same signal has less noise.

Visible imagery from GOES-15 and GOES-13 gives similar views of the developing tropical system off the coast of Yucatan, in part because the satellites are only separated by 15 degrees of longitude (GOES-13 sits on the Equator at 75 degrees West Longitude)

GOES-15 imager data differs from GOES-11. Whereas GOES-11 has a 12.0 micrometer channel, which is useful for observations of dust and ash (when used in conjunction with the 10.7 micrometer channel), GOES-15 has a 13.3 micron channel, which data are useful for cloud-top properties.

GOES 15/GOES 13 Imager Water Vapor loop

The GOES-15 Imager water vapor channel has 4-km resolution versus 8-km resolution on GOES-11. In the loop above, note the better depiction of gradients (despite the vastly different view angles) and the better depiction of the mid-level vortex at the southwest edge of the image.

Another comparison of 8-km resolution GOES-11 6.7 µm water vapor images with corresponding 4-km resolution GOES-15 6.5 µm water vapor images can be seen below, viewing a lobe of middle-tropospheric vorticity that was moving southeastward over Nunavut, Canada (GOES water vapor image with an overlay of GFS 500 hPa vorticity). Again, the satellite viewing angles are different, but the features and gradients (even at the high latitude of 65 degrees North) are much clearer on the GOES-15 water vapor images.

GOES-11 6.7 µm (top panels) and GOES-15 6.5 µm water vapor channel images (bottom panels)

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