Atlantic Tropical Invest 90L

May 23rd, 2010 |
GOES-13 visible images + lower-tropospheric atmospheric motion vectors

GOES-13 visible images + lower-tropospheric atmospheric motion vectors

An animation of GOES-13 visible images from the CIMSS Tropical Cyclones site (above) showed the development of a discrete low-level cyclonic circulation associated with the first Atlantic Basin tropical cyclone “Invest” of the season on 23 May 2010. An overlay of lower-tropospheric atmospheric motion vectors (along with a handful of ship reports) also showed a broad cyclonic circulation around this developing cloud feature.

GOES-13 IR images (below) showed that there were some large clusters of cold-topped convection located off to the northeast, but this deep convection did not appear to be directly related to the developing low-level cyclonic circulation seen on visible imagery.

GOES-13 IR images

GOES-13 IR images

GOES-13 water vapor imagery with an overlay of deep layer (850-200 hPa) wind shear (below) showed 2 factors present that were unfavorable for the rapid intensification of Invest 90L: very dry air aloft moving in from the west, along with increasing values of wind shear — however, model guidance suggested that there was a small chance that this system could eventually develop into a subtropical cyclone.

GOES-13 water vapor images + deep layer wind shear

GOES-13 water vapor images + deep layer wind shear

Violent “wedge” tornado in South Dakota

May 22nd, 2010 |
POES AVHRR 11.0 µm IR image + SPC storm reports

POES AVHRR 11.0 µm IR image + SPC storm reports

AWIPS images of the 1-km resolution POES AVHRR 11.0 µm IR channel data (above) showed a detailed view of the severe thunderstorm that produced a very large and violent “wedge” tornado that was responsible for EF4 damage in northeastern South Dakota on 22 May 2010. The coldest IR brightness temperature on the image was -77º C. An overlay of the corresponding SPC storm reports is also shown; this storm also produced hail up to 1.75 inch in diameter.

A comparison of the AVHRR IR image with the corresponding 0.63 µm visible channel image (below) revealed a large storm top plume that appeared to be spreading out northeastward from one of the overshooting tops located near the South Dakota / North Dakota border.

POES AVHRR 11.0 µm IR and 0.63 µm visible channel images

POES AVHRR 11.0 µm IR and 0.63 µm visible channel images

Classic “Enhanced-V” IR storm top signature in Texas

May 18th, 2010 |
AVHRR 12.0 µm IR + SPC tornado/hail reports + cloud-to-ground lightning

AVHRR 12.0 µm IR + SPC tornado/hail reports + cloud-to-ground lightning

An AWIPS image of the 1-km resolution POES AVHRR 12.0 µm IR channel data (above) displayed a classic and well-defined example of an “Enhanced-V” storm top signature over the northern Texas Panhandle region on 18 May 2010. Overlays of SPC storm reports and cloud-to-ground (CG) lightning strikes near the time of the image showed that this severe thunderstorm was producing hail as large as 2.75 inch in diameter, as well as a couple of tornadoes — and there were a large number of CG strikes within the Enhanced-V signature. The coldest cloud top IR brightness temperature was -74º C.

The corresponding 4-km resolution GOES-13 10.7 µm IR image (below) did exhibit an Enhanced-V signature, but the details were not as well-defined at the coarser spatial resolution. The coldest cloud top IR brightness temperatures were also about 10º C warmer on the GOES-13 image.

GOES-13 10.7 µm IR image

GOES-13 10.7 µm IR image

As part of the GOES-R Proving Ground activities to support the SPC Hazardous Weather Testbed, an Overshooting Top product is being generated by CIMSS. A 24-hour composite of the Overshooting Top (OT) hits is shown below, with a number of OT hits seen across the northern Texas panhandle.

GOES-13 Overshooting Tops product

GOES-13 Overshooting Tops product

Update on the Deepwater Horizon oil slick in the Gulf of Mexico

May 11th, 2010 |
MODIS true color (bands 1/4/3) and false color (bands 7/2/1) RGB images

MODIS true color (bands 1/4/3) and false color (bands 7/2/1) RGB images

A comparison of MODIS true color (using bands 1/4/3) and false color (using bands 7/2/1) Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) again revealed the areal extent of the surface portion of the oil slick just off the Louisiana coast in the northern Gulf of Mexico on 11 May 2010.

An animation of MODIS true color RGB images (created using bands 1/4/3) from days when the geometry of the sun glint was favorable (below) showed the changes in areal coverage and shape of the surface oil slick feature during the 21 days following the Deepwater Horizon offshore oil rig explosion (which occurred late in the evening on 20 April: CIMSS Satellite Blog | VISIT Meteorological Interpretation Blog). The first image on 21 April shows the smoke plume drifting southeastward from the oil rig site (before it eventually collapsed).

MODIS true color images (21, 22, 25, and 29 April and 01, 04, 08, 09, 10, and 11 May)

MODIS true color images (21, 22, 25, and 29 April and 01, 04, 08, 09, 10, and 11 May)

With the use of the 16-channel ABI instrument on the upcoming GOES-R satellite, the capability to generate and display these types of RGB images will be possible at high temporal resolution (every 5 minutes on a routine basis).

===== 17 MAY UPDATE =====

MODIS visible image + MODIS Sea Surface Temperature (SST) product

MODIS visible image + MODIS Sea Surface Temperature (SST) product

AWIPS images of MODIS 0.65 µm visible channel data and the MODIS Sea Surface Temperature (SST) product on 17 May 2010 (above) revealed that a long, thin portion of the oil slick had been drawn southward and southeastward, possibly becoming entrained into the far northern circulation of the Gulf of Mexico Loop Current. The MODIS SST values within the Loop Current were very warm — as high as 82º F (darker red color enhancement).

A closer view using 250-meter resolution MODIS true color (using bands 1/4/3) and false color (using bands 7/2/1) RGB images from the SSEC MODIS Today site (below) showed better detail of the long oil slick plume that was moving southward.

It is unclear why the far eastern end of the oil slick plume appears so dark on the MODIS images; one idea is that a great deal of oil dispersant had been spread over the leading edge of the plume, which then greatly reduced the amount of solar energy being reflected back up toward the satellite. Or, perhaps the darker area is oil along the leading edge of the plume that is still sub-surface?

MODIS true color (using bands 1/4/3) and false color (using bands  7/2/1) images

MODIS true color (using bands 1/4/3) and false color (using bands 7/2/1) images

For addition details, see the Weather Underground blog.