Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

The VIIRS instrument on Suomi NPP yielded compelling nighttime imagery of Hurricane Gonzalo in the western Atlantic. The toggle above of the Day Night Band and the 11.45 µm Infrared imagery shows a circular central dense overcast over the storm (imagery courtesy of William Straka, CIMSS). No eye structure is immediately apparent, although very cold cloud tops are present at the storm center. A larger-scale view of the Day Night Band and 11.45 µm imagery, below, shows a storm in a low to moderate wind shear environment with a well-defined outflow channel to the northeast. Note the pronounced “transverse banding” signature along the southern periphery of the hurricane – such transverse banding is often seen in areas of high-altitude of turbulence. Gonzalo was forecast to strengthen (see the National Hurricane Center website for more details).

Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

During the subsequent daytime hours on 14 October, Hurricane Gonzalo did indeed continue to intensify, becoming a Category 3 storm by the late afternoon (ADT plot). The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-7 minutes; 0.63 µm visible channel images (below; click image to play animation; also available as an MP4 movie file) showed periodic convective bursts around the eye of Gonzalo as the tropical cyclone moved northwestward.

GOES-13 0.63 µm visible channel images (click to play animation)

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Suomi NPP 11.35 µm Infrared Imagery, 1933 UTC 13 October 2014, with Lightning strike data overlain (click to enlarge)

An intense extratropical cyclone over the central United States spawned a Quasi-Linear Convective System that moved through the Deep South on 12-13 October 2014; the QLCS was responsible for a spate of severe weather including wind damage, hail and tornadoes (Storm reports from 12 October, 13 October). The image above, from 1933 UTC on 13 October, shows Suomi NPP 11.35 µm imagery over Mississippi. Widespread cold cloud tops are apparent, with embedded overshooting tops. Indeed, the top in southern Hinds County may have been associated with severe Hail. Visible imagery from Suomi NPP (link) also show overshooting tops. The amount of solar reflectance at mid-day, however, makes it difficult to identify all features. The 1.61 µm imagery, below, is darker because ice crystals at cloud top will absorb some energy at that wavelength, yet most features are still recognizable.

Suomi NPP 1.61 µm Near-Infrared Imagery, 1933 UTC 13 October 2014 (click to enlarge)

The GOES-13 Water Vapor Animation, below, is a textbook example of cyclogenesis. Strong sinking in and around the comma head is indicated by the warm water vapor brightness temperatures observed there. This system is also characterized by a very sharp upstream trough and developing warm conveyor belt that turns anticyclonic as it moves over the upper Great Lakes.

GOES-13 Water Vapor 6.7 µm Infrared Imagery, 1200-2100 UTC 13 October (click to animate)

GOES-13 10.7 infrared imagery animation, below (also available here as an mp4 file or here as a YouTube video), shows evidence of many overshooting tops in the strong thunderstorms that developed across the deep south. (Indeed, automatic detection of overshooting tops — (and cumulative totals from this website) — show some on the 12th, but many more on the 13th) as the extratropical cyclone became organized.

GOES-13 10.7 µm Infrared Imagery, 1600 UTC 13 October – 0700 UTC 14 October 2014 (click to animate)

The strong system enjoyed a vigorous moisture feed from the Gulf of Mexico, as shown in the MIMIC Total Precipitable Water animation below. Moisture surged northward especially after 1200 UTC on 13 October, and the 24-hour precipitation totals ending at 1200 UTC on 14 October (from this site) showed heavy rain over much of Tennessee and Alabama (and adjacent states).

MIMIC Total Precipitable Water for 72 hours 1200 UTC 14 October 2014 (click to enlarge)

GOES Sounder data also shows a quick moistening on 13 October as high Precipitable Water air over the Gulf of Mexico surges northward. Moisture from Pacific Hurricane Simon is unlikely to be a contributing factor to this storm.

MIMIC Total Precipitable Water for 72 hours 1200 UTC 14 October 2014 (click to enlarge)

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MTSAT-2 and GOES-15 Water Vapor (6.5 µm)Infrared imagery, times as indicated (click to enlarge)

An interesting question arises: Where did some of the energy and moisture for this (somewhat early in the season) storm originate? Water Vapor imagery from MTSAT-2 and GOES-15 show clearly that the Super-Typhoon Phanfone, that was near Japan on 4-5 October, contributed some of the energy to the impulse that moved across the Pacific Ocean and then over the Ridge on the West Coast of North America before diving southeast and forcing cyclogenesis. In the animation above, Phanfone approaches Japan, and is picked up by a mid-latitude jet that crosses the Pacific (tracked by red arrow), induces strong cyclogenesis in the Gulf of Alaska on 8 October and then continues up and over the ridge on the west coast of North America.

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GOES-13 6.5 µm water vapor channel images (click to play animation)

A large mid-latitude cyclone exhibited explosive development over the North Atlantic Ocean (south of Greenland) on 13 October 2014. This storm produced hurricane-force winds, according to surface analyses from the Ocean Prediction Center. GOES-13 6.5 µm water vapor channel images (above; click image to play animation; also available as an MP4 movie file) showed the intrusion of very dry air (yellow to orange color enhancement) associated with the approach of a potential vorticity anomaly early in the day, followed by the the cyclone wrapping up after it reached the occluded phase during the afternoon hours.

GOES-13 0.63 µm visible channel images (below; click image to play animation) revealed the very pronounced signature of cold air advection from the western to the southern quadrants of the storm, in the form of open-cell and closed-cell convective clouds.

GOES-13 0.63 µm visible channel images (click to play animation)

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GOES-13 0.63 µm Visible Imagery, 13 October (click to play animation)

Tropical Storm Gonzalo is moving through the Leeward Islands today, October 13. The animation above shows the visible imagery from GOES-13. Slow strengthening of the storm is indicated. Eye formation may be occurring in the later part of the animation. (Note that imagery over the Leeward Islands is available only every half-hour because of an RSO called for GOES-13 associated with severe weather; in normal operations, the Caribbean is scanned every 15 minutes as discussed here).

Suomi NPP Day Night Band visible (0.70 µm) and 11.35 µm infrared imagery at 0456 UTC, 13 October (click to enlarge)

Suomi NPP overflew the developing system at 0456 UTC on 13 October, and a toggle between the Day Night Visible Band and the 11.35 infrared imagery (courtesy of W. Straka, CIMSS) is above. Cold cloud tops associated with numerous overshooting tops are obvious. (Click here for a graph of the number of overshoots as detected from GOES-13 as a function of time)

Saharan Air Analysis from Meteosat, 1200 UTC 12 October through 1200 UTC 13 October (click to play animation)

The Atlantic Tropical Storm season has been comparatively quiet this year in part because of strong Saharan Air Layer events (discussed in Blog Posts here and here). When this dry air that originates over the Sahara moves over the tropical Atlantic, the convection necessary for tropical storm formation is suppressed. Lately, however, Saharan Air Layer events have decreased, and tropical systems are developing in the tropical Atlantic. The 24-hour animation above (from CIMSS Tropic Web site) shows very little Saharan Air over the Atlantic, and two named storms — Fay (at 50 º W on the northern border of the domain) and Gonzalo (approaching the Leeward Islands) — are present. In addition, a strong tropical wave is moving across the tropical Atlantic at 15 º N, 40 º W. MIMIC Total Precipitable Water animations (below) also show a moist environment over much of the tropical Atlantic.

MIMIC Total Precipitable Water for the 72 hours ending 1200 UTC 13 October 2014 (click to enlarge)

GOES-13 10.8 µm Infrared Imagery every six hours from 2045 UTC 12 October through 1445 UTC 13 October (click to play animation)

A storm-centered animation of the 10.8 µm imagery from GOES-13, above, shows the gradual organization of Gonzalo as it moved towards the Leeward Islands. In particular, between 0845 and 1445 UTC on 13 October (the last two images in the 4-frame loop), a central dense overcast (CDO) has formed, and outflow to the east has become established. Gonzalo’s projected path (see below, from here) is over very warm water, and through an atmosphere with little shear; slow strenghtening is expected. See the National Hurricane Center website for more details, including warnings for the Leeward Islands.

Analyses of Sea Surface Temperatures and Shear, 1200 UTC 13 October 2014 (click to enlarge)

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