Suomi NPP VIIRS Sea Surface Temperature (SST) product

A sequence of four AWIPS images of the Suomi NPP VIIRS Sea Surface Temperature (SST) product (above) showed very detailed information about the SST patterns in the Gulf of Mexico on 21 January 2015. Two features in particular are worth noting: (1) what appears to be a train of Kelvin-Helmholtz instability waves along one of the northern boundaries of the Loop Current (best seen on the 06:52 UTC image), and (2) a small-scale cyclonic eddy located between the far northern edge of the Loop Current and the Mississippi River Delta. On the final 19:57 UTC image, SST values in the general region of this small-scale eddy ranged from 46.7º F at the Mississippi River Delta (cyan color enhancement) to 79.7º F (darker red color enhancement) near the northern edge of the Loop Current – a difference of 33º F within a distance of only about 100 miles.

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MIMIC Total Precipitable Water product, with Tropical Surface Analyses (click to play animation)

AWIPS images of the MIMIC Total Precipitable Water product (above; click image to play animation) showed a broad moist plume in the equatorial South Pacific Ocean, within which Tropical Storm Niko began to develop during the 19 January – 20 January 2015 period. By the end of the animation, Gale Force winds were being analyzed within the eastern semicircle of the developing cyclone. Metop ASCAT surface scatterometer winds at 08:01 UTC (below) showed winds as strong as 42 knots (though the direction of the stronger yellow wind barbs was suspect, likely due to rain contamination).

MIMIC TPW product, with Metop ASCAT surface scatterometer winds

After daybreak on 20 January, McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (below; click image to play animation) showed the development of spiral banding wrapping into the central low-level circulation center as the system reached tropical storm intensity by 18 UTC.  In addition, a few strong convective pulses with distinct overshooting tops could be seen near the core of Niko.

GOES-15 0.63 µm visible channel images (click to play animation)

An animation of GOES-15 10.7 µm IR channel images from the CIMSS Tropical Cyclones site (below) included an overlay of contours of the deep layer (200 – 850 hPa) wind shear at 18 UTC — Tropical Storm Niko developed in a region characterized by low wind shear, which enabled the storm to rapidly intensify.

GOES-15 10.7 µm IR channel images, with contours of deep layer wind shear

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SSEC RealEarth™ Infrared satellite image featured on NBC Nightly News

The SSEC RealEarth™ geostationary satellite infrared (IR) image composite shown above (which was first sent out via Twitter by Stu Ostro of The Weather Channel…thanks Stu!) was featured on the NBC Nightly News on 14 January 2015 (link) because it illustrated a vivid example of the trans-Atlantic flow of moisture from a disturbance off the US East Coast to a rapidly-deepening storm approaching the British Isles (surface analysis maps | water vapor images with surface analyses).

A sequence of hourly geostationary satellite water vapor channel image composites (below; click to play animation) showed that there was a clear trans-Atlantic connection in terms of middle to upper tropospheric moisture/clouds, and a comparison of the 20 UTC water vapor image with the corresponding MIMIC Total Precipitable Water product indicated that there was a lower to middle tropospheric moisture connection as well. This type of long and narrow fetch of TPW is often referred to as an “atmospheric river”.

Geostationary satellite water vapor image composites (click to play animation)

Another interesting point brought up during the NBC Nightly News segment was the recent presence of unusually strong trans-Atlantic jet stream winds, which has allowed aircraft flying from New York City to London to set record times in terms of conventional passenger aircraft (such as the 08 January flight of British Airways 114). Note the strong dry-to-moist (darker blue to white to green color enhancement) along the northern edge of the trans-Atlantic water vapor image moisture feed: such a moisture gradient often coincides with the axis of a strong jet stream. AWIPS images of water vapor imagery with overlays of MADIS cloud-tracked and water-vapor-tracked winds (below; click image to play animation) showed many high-altitude wind vectors in the vicinity of the jet stream moisture gradient with speeds in the 150-160 knot range (with 175 knots seen on the previous day).

Water vapor images with MADIS atmospheric motion vectors (click to play animation)

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Advanced Dvorak Technique (ADT) intensity estimate

A plot of the Advanced Dvorak Technique intensity estimate for Tropical Cyclone Bansi (above) showed that the storm experienced a period of rapid intensification late in the day on 12 January 2015, reaching Category 4 intensity by 00 UTC on 13 January.

EUMESAT Metosat-7 11.5 µm IR channel images (below; click to play animation; also available as an MP4 movie file) revealed the formation of a well-defined eye, which also exhibited a notable amount of trochoidal motion or “wobble” as it moved across the southwest Indian Ocean (north of Reunion and Mascarene Island).

Meteosat-7 11.5 µm IR channel images (click to play animation)

A more detailed view of Tropical Cyclone Bansi was provided by McIDAS-V images of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band data (below; credit: William Straka, SSEC) — deep convection with overshooting tops could be seen in the southern quadrant eyewall region, with gravity waves propagating radially outward across the northeastern and eastern portion of the cirrus canopy.

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

A DMSP SSMIS 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed that a prominent “moat” of warm brightness temperatures (darker blue color enhancement) existed around the center of Bansi at 14:24 UTC on 13 January. The presence of such a moat usually signifies that the secondary (outer) eyewall formation process has completed, and an eyewall replacement cycle is underway (also signalling that the period of rapid intensification has ended). The moat feature is sustained by subsidence from the eyewall secondary circulations.

DMSP SSMIS 85 GHz microwave image

Note that there was no well-defined eye evident on the conventional Meteosat-7 IR image during this eyewall replacement cycle (below).

Meteosat-7 11.5 µm IR channel and DMSP SSMIS 85 GHz microwave images

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