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

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

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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

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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

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

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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

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GOES-13 0.63 µm visible images

AWIPS images of GOES-13 0.63 µm visible channel data (above) showed widespread hazy conditions over much of the Great Lakes region during the afternoon and evening hours on 24 June 2010. The thick haze became more evident during the late afternoon and early evening hours, as a more favorable sun angle for “forward scattering” helped to highlight the airborne aerosols.

The MODIS Aerosol Optical Depth (AOD) product (below) indicated that AOD values over much of the Great Lakes region were in the 0.6 to 0.8 range, with a larger area of AOD values near 1.0 over south-central Canada. A large number of wildfires had been burning across the northern Prairie Provinces of Canada during the preceding days — so could this thick haze seen over the Great Lakes be due to smoke from Canadian fires?

MODIS Aerosol Optical Depth (AOD) product

A comparison of 1-km resolution MODIS 0.65 µm visible and 3.7 µm shortwave IR images (below) depicted a number of smoke plumes and “hot spots” (orange to yellow color enhancement) from fires that were still burning on 24 June over northern Saskatchewan and Manitoba. However, on this day, surface winds were from the southeast, advecting the smoke plumes toward the northwest.

MODIS 0.65 µm visible channel and 3.7 µm shortwave IR images

A comparison of the 1-km resolution MODIS and AVHRR 3.7 µm shortwave IR images with the corresponding 4-km resolution GOES-13 3.9 µm shortwave IR image (below) demonstrated the improvement in fire hot spot detection and geo-location using the 1-km resolution polar orbiting satellite data — note the mapping errors on the GOES-13 image due to the large viewing angle from the geostationary satellite.

MODIS 3.7 µm, AVHRR 3.7 µm, and GOES-13 3.9 µm shortwave IR images

Over southern Wisconsin, the thick smoke contributed to colorful yellow to orange sunset, as seen using the AOSS rooftop camera at the University of Wisconsin – Madison (below; also available as a QuickTime animation).

AOSS rooftop camera image (facing to the west)

Lidar data from the UW-Madison SSEC Lidar Group (below) showed enhanced backscatter within the 1-2 km altitude layer during the daytime hours.

Lidar backscatter data from the SSEC Lidar Group at UW-Madison

NOAA ARL HYSPLIT back trajectories (below) confirmed that air parcels arriving over Madison, Wisconsin on 24 June had likely passed over the parts of northern Saskatchewan 2-3 days earlier, where active fires had been burning for several days.

NOAA ARL HYSPLIT backward trajectories (arriving over Madison, Wisconsin)

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