Hurricane Alex

June 30th, 2010
GOES-13 10.7 µm IR imagery

GOES-13 10.7 µm IR imagery

GOES-13 10.7 µm IR imagery from the CIMSS Tropical Cyclones site (above) showed the development of large convective bursts around the center of Hurricane Alex during the 29 June30 June 2010 period. Alex became the first June hurricane in the Atlantic Basin since the 1995 tropical cyclone season (which produced Hurricane Allison).

An AWIPS image of POES AVHRR 11.0 µm IR channel data (below) showed very cold IR brightness temperatures of -80 to -90º C (violet color enhancement) associated with the convective bursts as well as the distant bands of intense convection surrounding the hurricane.

POES AVHRR 10.8 µm IR image

POES AVHRR 10.8 µm IR image

Deep layer wind shear (below) over the western Gulf of Mexico remained very light, which was favorable factor for further intensification prior to making landfall.

GOES-13 IR image + deep layer wind shear

GOES-13 IR image + deep layer wind shear

DMSP SSMI/S 85 GHz microwave imagery (below) showed the possible development of some inner banding structure, as well as the larger and more intense bands of convection far from the center of Alex.

SSMI/S microwave image

SSMI/S microwave image

AWIPS images of the MIMIC Total Precipitable Water product (below) indicated that a rich source of moisture remained in place across the entire Gulf of Mexico region (with TPW values in excess of 60 mm).

MIMIC Total Precipitable Water product

MIMIC Total Precipitable Water product

UPDATE: AWIPS images of the MODIS 0.65 µm visible and 11.0 µm IR channel data with an overlay of ASCAT scatterometer surface winds (below) depicted the eye of Hurricane Alex at 16:58 UTC on 30 June.

MODIS 0.655 µm visible and 11.0 µm IR images + ASCAT scatterometer winds

MODIS 0.655 µm visible and 11.0 µm IR images + ASCAT scatterometer winds

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POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

Later in the day, AWIPS images of the POES AVHRR Cloud Top Temperature (CTT), Cloud Top Height (CTH), and Cloud Type products at 22:05 UTC (above) displayed a large area of CTT values in the -80 to -83º C range (violet color enhancement), with CTH values as high as 17 km (darker blue color enhancement). The Cloud Type product categorized a large portion of the coldest/highest cloud tops surrounding the eye as “overshooting(lighter violet color enhancement), in general agreement the the GOES InfraRed/Water Vapor difference overshooting top detection technique of Olander and Velden (2009).


GOES-15 and GOES-13 0.63 µm visible channel images

GOES-15 and GOES-13 0.63 µm visible channel images

The eye of Hurricane Alex became more well-defined on GOES visible imagery as it approached the coast of Mexico, as seen on a comparison of GOES-15 and GOES-13 visible images at 15 minute intervals (above) and also on GOES-13 Rapid Scan Operations (RSO) images at 5-10 minute intervals (below). An impressive convective burst was evident just as the eye was nearing the coastline — in fact, Alex rapidly intensified into a 90 knot Category 2 hurricane just prior to making landfall, as can be seen on this plot of the CIMSS Automated Dvorak Technique. This made Alex the first Category 2 or stronger hurricane to occur in the month of June since Hurricane Alma back in 1966.

GOES-13 0.63 µm visible channel images (Rapid Scan Operations)

GOES-13 0.63 µm visible channel images (Rapid Scan Operations)

Tropical Storm Alex in the Bay of Campeche

June 28th, 2010

Tropical Storm Alex, which formed over the northwestern Caribbean Sea out of a westward-moving tropical wave on Friday and Saturday, emerged overnight into the Bay of Campeche from the Yucatan Peninsula. Since emerging from that landmass as a tropical depression (signifying sustained winds weaker than 35 knots), it has strengthened back to Tropical Storm status. Current forecasts place it as a hurricane — possibly major — near the northern Mexico Gulf Coast later this week.

The large-scale environment is favorable for strengthening. For example, the MIMIC Total Precipitable Water loop (here) shows an environment that is rich in moisture over the Gulf of Mexico. (Note also the apparent Fujiwara interaction between Alex and Pacific Tropical Depression Darby, as they start to circulate around a common center.) The general west-northwestward drift of the feature is also readily apparent, as are the tropical systems Celia and Darby in the Pacific Ocean. The projected path of the storm takes it over warm sea surface temperatures with abundant Oceanic Heat Content. In addition, the environment is one of low shear that is decreasing with time. (Images of these products are available at the CIMSS Tropical Cyclone Web page.)

10.8-micron imagery from the AVHRR on NOAA-15 on the morning of 28 June (above) shows Brightness temperatures around -80 C in the strong convection around the center of Alex.

MODIS 11.0 µm IR image

MODIS 11.0 µm IR image

Update: MODIS 11.0 µm IR imagery (above) revealed cloud top IR brightness temperatures as cold as -92º C (darkest purple color enhancement) associated with some of the intense convection  around Alex at 18:53 UTC. These areas of very cold cloud top were identified as “overshooting tops” (overshooting the tropopause) by the IR / Water vapor difference product (reference: “Tropical Cyclone Convection and Intensity Analysis Using Differenced Infrared and Water Vapor Imagery”, Olander and Velden, 2009) from the CIMSS Tropical Cyclones site (below).

GOES-13 Overshooting Top (IR / Water vapor difference) product

GOES-13 Overshooting Top (IR / Water vapor difference) product

Category 5 Hurricane Celia

June 25th, 2010

GOES-11 IR images

GOES-11 IR images

Hurricane Celia became the first Category 5 tropical cyclone of the 2010 East Pacific season on 24 June — in fact, the 140 knot intensity of Celia tied with Hurricane Ava (1973) as the strongest East Pacific Basin hurricane on record during the month of June. GOES-11 IR images from the CIMSS Tropical Cyclones site (above) displayed an annular structure with a well-defined small diameter eye as the hurricane began to slowly weaken on 25 June 2010.

85 GHz microwave imagery from the SSM/I instrument (below) also revealed the nearly symmetric structure of the eye of the Celia.

SSMI/S 85 GHz microwave imagery

SSMI/S 85 GHz microwave imagery

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Terra MODIS 11.0 µm IR image

Terra MODIS 11.0 µm IR image

McIDAS images of Terra MODIS 11.0 µm IR channel data (above) showed the well-defined eye of Celia during the pre-dawn hours on 25 June, while GOES-11 0.65 µm visible channel images (below) show the evolution of the eye later in the day.

GOES-11 0.65 µm visible images

GOES-11 0.65 µm visible images

On the previous day (24 June) — as Celia was rapidly intensifying (CIMSS ADT plot) — the tropical cyclone exhibited  IR brightness temperature values as cold as -91º C at 07:30 UTC on GOES-11 10.7 µm IR images (below).

GOES-11 10.7 µm IR images

GOES-11 10.7 µm IR images

Update on the Gulf of Mexico oil slick

June 25th, 2010
MODIS true color (using bands 1/4/3) and false color (using bands 7/2/1) RGB images

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

A comparison of 250-meter resolution MODIS true color (created using bands 1/4/3) and false color (created using bands 7/2/1) images on 25 June 2010 from the SSEC MODIS Today site (above) showed the extent of the surface oil slick from the Deepwater Horizon offshore oil rig accident.

AWIPS images of early morning POES AVHRR 0.63 µm visible and 3.7 µm shortwave IR data (below) revealed a thin smoke plume drifting northwestward from a small fire hot spot (orange color enhancement) due to a fire that was set to burn off some of the surface oil.

POES AVHRR 0.63 µm visible and 3.7 µm shortwave IR images

POES AVHRR 0.63 µm visible and 3.7 µm shortwave IR images