GOES-12 3.9 µm shortwave IR channel images (click image to play animation)

As a result of prolonged drought and a mid-summer heat wave across southern Chile, a number of wildfires were burning in parts of the region on 01 January – 02 January 2012 (surface analysis). GOES-12 3.9 µm shortwave IR images (above; click image to play animation) showed a number of fire “hot spots” (yellow to red color enhancement) between Concepcion (station identifier SCIE) and Chillan (station identifier SCCH) from the late afternoon on 01 January until the early morning hours on 02 January.

During the subsequent daytime hours, GOES-12 0.63 µm visible channel images (below; click image to play animation) revealed a long hazy smoke plume that was drifting northwestward out over the adjacent Pacific Ocean. As daytime heating increased, cumulus clouds with a few thunderstorms could also be seen developing farther inland over the higher terrain of the Andes Mountains.

GOES-12 0.63 µm visible channel images (click image to play animation)

Rawinsonde data from Santo Domingo (station identifier SCSN) at 12 UTC indicated that southeasterly winds existed near the top of the deep temperature inversion, between 741 hPa (2.6 km) and 700 hPa (3.1 km) — so this is likely the approximate altitude of the smoke plume seen drifting toward the northwest on the GOES-12 visible satellite imagery.

Santo Domingo, Chile rawinsonde data plot

A high-resolution MODIS true color image of the fire smoke plume can be seen on the NASA Earth Observatory site.

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EUMETSAT Meteosat-9 High Resolution Visible (HRV) images

EUMETSAT Meteosat-9 High Resolution Visible (HRV) images (above) showed the classic signature of a “warm seclusion“: a nearly cloud free eye-like structure at the center of the circulation. Surface station wind barbs (in knots) are also plotted in cyan on the images.

A similar eye-like appearance was seen on Meteosat-9 water vapor channel images (below) as the mature cyclone moved just north of the British Isles on 28 December 2011.

EUMETSAT Meteosat-9 water vapor channel images

Hurricane force wind gusts were observed at Tiree, Scotland (station identifier EGPU), with a peak gust of 69 knots (79 mph) at 14:20 UTC (below).

Tiree, Scotland (EGPU) surface reports

Surface analyses from the NWS/NCEP Ocean Prediction Center (below) showed the intensification and evolution of the cyclone during the day.

Ocean Prediction Center surface analyses

Warm seclusions are also sometimes observed with intense cyclones along the East Coast of the US, as in this 20 December 2009 case.

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MTSAT-1R 10.8 µm IR channel images

MTSAT-1R 10.8 µm IR channel images from the CIMSS Tropical Cyclones site (above) showed Category 1 Tropical Storm Thane (06B) in the Bay of Bengal, moving toward the east coast of India on 28 December 2011.

Contours of 850-200 hPa satellite-derived deep layer wind shear overlaid on MTSAT-1R 6.75 µm water vapor channel images (below) indicated that Thane was in an environment of low wind shear, which favored some intensification prior to making landfall.

MTSAT-1R 6.75 µm water vapor channel images + Deep layer wind shear

It is interesting to note that the MIMIC Total Precipitable Water product (below) showed the northern counterclockwise circulation of Tropical Storm Thane and the southern clockwise circulation of Tropical Storm Four (04S) — each drawing moisture from the Inter-Tropical Convergence Zone (ITCZ).

MIMIC Total Precipitable Water product

===== 30 December Update =====

Tropical Storm 04 S intensified in a similar low wind shear environment, becoming Tropical Cyclone Benilde in the South Indian Ocean. Benilde was forecast to intensify, with wind gusts up to 140 knots. Meteosat-7 visible/shortwave IR images with an overlay of ASCAT scatterometer surface winds (below) showed the structure of Benilde.

Meteosat-7 visble/shortwave IR imagery + ASCAT surface winds

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GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (click image to play animation)

Strong winds aloft associated with a cyclonically-curved jet streak over the Northern Rocky Mountains were responsible for a number of mountain waves and lee “banner clouds” over parts of Wyoming and Montana on 25 December – 26 December 2011. A side-by-side comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (above; click image to play animation) revealed some interesting differences in the appearance of these mountain waves. Note that the images are displayed in the native projection of their respective satellites.

A comparison of the GOES-15 and GOES-13 imager 6.5 µm water vapor channel weighting functions (below) showed that the satellite viewing angles (or satellite zenith angles) were very close — 56.41 degrees for GOES-15, and 59.95 degrees for GOES-13 — and the weighting function profiles were nearly identical. However, the fact that GOES-15 was viewing the region from the west allowed it to better resolve the warm/dry signatures (yellow color enhancement) of the most pronounced sinking regions associated with some of the stronger mountain waves. These warm/dry subsidence signatures were possibly masked by the high-altitude lee banner clouds when viewed from the east with GOES-13.

GOES-15 vs GOES-13 water vapor channel weighting function profiles

At 00:40 UTC there was one pilot report of brief moderate turbulence at an altitude of 37,000 feet near the Wind River Range in west-central Wyoming (below). Only a lee banner cloud was evident on the GOES water vapor imagery at that particular time, but a few hours later the warm/dry signature of strong mountain wave subsidence started to become more distinct over that location.

GOES-13 6.5 µm water vapor channel image + pilot report of turbulence

Had higher spatial resolution water vapor imagery been available closer to the 00:40 UTC time of the turbulence encounter, perhaps a more distinct mountain wave signature might have been apparent. For example, a comparison of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-13 6.5 µm water vapor images at 05:01 UTC (below) demonstrated the advantage of improved spatial resolution water vapor imagery for identifying subtle mountain wave signatures across the region.

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

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