Cyclone Sidr makes landfall in Bangladesh

November 15th, 2007 |

NOAA-17 IR image

A NOAA-17 InfraRed (IR) image (above) depicted a well-defined eye and eyewall structure associated with Category 4 Cyclone Sidr while it was located over the Bay of Bengal on 15 November 2007. The CIMSS Advanced Dvorak Technique (ADT) intensity estimate around that time was 146 knots.

MIMIC (Animated GIF)

Animations of the Morphed Integrated Microwave Imagery at CIMSS (MIMIC) (above) showed Cyclone Sidr as it approached the coast of Bangladesh. This CIMSS MIMIC product was also featured on The Weather Channel by their tropical weather expert Dr. Steve Lyons (below).

MIMIC on The Weather Channel

Meteosat-7 IR images (below) indicated that Cyclone Sidr made landfall around 14:00 UTC between Calcutta, India (station identifier VECC) and Chittagong, Bangladesh (station identifier VGEG). Media reports suggest that the death toll in Bangladesh resulting from Cyclone Sidr is now greater than 3100 people.

Meteosat-7 IR images (Animated GIF)

Tropical Cyclone Sidr

November 14th, 2007 |

Meteosat-7 IR images (Animated GIF)

Meteosat-7 IR images sourced from the CIMSS Tropical Cyclones site (above) showed Category 4 intensity Tropical Cyclone Sidr as it moved northward across the Bay of Bengal on 14 November 2007. Increasing amounts of deep layer wind shear (below) to the north of the storm may act to diminish the intensity of Sidr somewhat as it approaches land, but catastrophic storm surge flooding will still be a danger across much of the flood-prone flat river delta regions along the coast of Bangladesh. A tropical cyclone with winds of 150 mph (240 km/hr) and a storm surge of 16-32 feet (5-10 meters) killed an estimated 500,000 people in Bangladesh in November 1970.

Meteosat-7 IR image + wind shear analysis

CIMSS Advanced Dvorak Technique intensity estimate

The CIMSS Advanced Dvorak Technique (ADT) plot (above) indicated an intensity estimate of 140 knots late in the day on 14 November — this was not long after the center of Sidr passed over a region of higher Ocean Heat Content over the Bay of Bengal (below).
Ocean Heat Content

Saharan dust outbreak

November 11th, 2007 |

METEOSAT-9 Saharan Air Layer tracking product (Animated GIF)

A major outbreak of Saharan dust was noted during the 06-11 November 2007 period — the Meteosat-9 Saharan Air Layer (SAL) tracking product (above) revealed an extensive signal of thick dust (orange to red enhancement) that was being transported westward across the tropical Atlantic.

The MIMIC Total Precipitable Water (TPW) product (below) showed the dry character of this large Saharan dust plume — TPW values as low as 10-20 mm (brown to violet enhancement) were seen over eastern and central portions of the tropical Atlantic basin as the dust and dry air layer streamed westward off the African continent.

MIMIC Total Precipitable Water (Animated GIF)

An animation of daytime Meteosat-9 “true color” image composites at 12 UTC and/or 18 UTC (below) shows the hazy appearance of the large Saharan dust plume. The appearance of such a strong Saharan dust event in November is curious in light of two recent studies by Evan et al.: (1) November appears to be the minimum of the seasonal Saharan dust cycle, and (2) August-September 2007 showed little to no dust storm activity over the tropical North Atlantic basin.

Meteosat-9 true color imagery (Animated GIF)

Noel transitions to an extratropical cyclone

November 3rd, 2007 |

GOES-12 water vapor images (Animated GIF)

As Hurricane Noel made the transition to an extratropical cyclone during the 02 to 03 November 2007 period, it remained a very large and very powerful storm system that significantly impacted the Atlantic coast regions of the northeastern US and southeastern Canada with hurricane force winds (91 mph at Horseshoe Shoal MA), heavy rain (4.83 inches at Bass Harbor ME), high seas (46.0 foot waves at Buoy 44011), and even heavy snow (6.0 inches at Fort Kent ME). AWIPS images of the GOES-12 6.5 µm “water vapor” channel (above) showed a very pronounced warm/dry band (orange enhancement) just south of the main cloud shield along the southern quadrant of the storm. This particular water vapor signature often indicates a potential for very strong winds at the surface as momentum from aloft is transferred downward into the boundary layer; the southern flank is also a favored area for strong surface winds in an extratropical cyclone.

An AWIPS image of the 6.7 µm MODIS water vapor channel around 02:45 UTC (below) with 03 UTC surface reports reveals that Fixed Buoy 41048 (located west of Bermuda, station ID TXKF) was situated near the leading edge of the water vapor dry band, and experienced a peak wind gust (from the south) of 62 knots near the time of the MODIS image. Buoy 41048 recorded a peak wind gust of 69 mph at 01:50 UTC, and a peak wave height of 37.1 feet at 02:50 UTC.

MODIS water vapor image + surface reports