Hurricane Alex

January 13th, 2016

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

Subtropical Storm Alex (NHC advisory archive) formed in the far eastern Atlantic Ocean on 13 January 2016. Animations of GOES-13 (GOES-East) 0.63 µm Visible (above) and 10.7 µm Infrared images (below) showed the initial evolution and northeastward motion of the storm. Alex is only the 4th known January tropical or subtropical storm to have formed in the Atlantic since the historical record began in 1851.

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Infrared (10.7 µm) images [click to play animation]

===== 14 January Update =====

A comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0320 UTC (below) showed the well-defined eye of Alex. With the Moon in the Waxing Crescent phase (at 30% of Full) there was enough illumination to demonstrate the “visible image at night” capability of the Day/Night Band. A magnified version of the Infrared image showing the eye can be seen here.

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

As of 15 UTC on 14 January, Alex had made the transition from subtropical storm to Category 1 hurricane (eastern Atlantic Ocean surface analyses). GOES-13 Infrared (10.7 µm) images (below) showed the well-defined eye that had formed. Alex became the first known hurricane to form in the Atlantic Ocean since 1938, and only the second hurricane on record to from north of 30ºN latitude and east of 30ºW longitude.

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Infrared (10.7 µm) images [click to play animation]

A DMSP-16 SSMIS Microwave (85 GHz) image (below) revealed the eye structure at 1653 UTC.

DMSP-16 SSMIS 85Ghz microwave brightness temperature image [click to enlarge]

DMSP-16 SSMIS 85Ghz microwave brightness temperature image [click to enlarge]

===== 15 January Update =====

While still classified as a hurricane, Alex was undergoing a weakening trend as it approached the Azores Islands during the early morning hours on 15 January. GOES-13 Infrared (10.7 µm) images (below) showed a strong convective band that produced a brief period of heavy rain at Ponta Delgata and Lajes Acores several hours prior to the passage of the eye of Alex (which occurred in the 11-14 UTC time frame — and Alex was downgraded at that point to a Tropical Storm). At Ponta Delgata a peak wind gust of 50 knots was recorded at 1130 UTC.

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Infrared (10.7 µm) images [click to play animation]

ISS-Rapidscat surface scatterometer winds (below) showed the center of circulation of Alex just south of the Azores Islands at 1118 UTC.

Rapidscat surface scatterometer winds [click to enlarge]

Rapidscat surface scatterometer winds [click to enlarge]

===== 16 January Update =====

Using a long animation of GOES-13 Water Vapor (6.5 µm) images covering the 06-16 January period (below; also available as a large 165-Mbyte animated gif), the origination of Hurricane Alex could be traced back to a strong baroclinic mid-latitude cyclone that rapidly intensified off the southeast coast of the US on 07 January.

GOES-13 Water Vapor (6.5 µm) images [click to play MP4 animation]

GOES-13 Water Vapor (6.5 µm) images [click to play MP4 animation]

The origin and motion of Alex could also be identified using the satellite-derived atmospheric motion vector 850 hPa Relative Vorticity product (below). A region of lower-tropospheric vorticity over Cuba on 06 January began moving northeastward across the Bahamas, then eastward across the Atlantic Ocean on 07 January.

850 hPa Relative Vorticity product [click to play animation]

850 hPa Relative Vorticity product [click to play animation]

For another perspective on the history of the development of Alex, see this article from The Weather Channel.

Tropical Storm Pali in the central Pacific

January 8th, 2016

Himawari-8 Water Vapor (6.2 µm) infrared Imagery [click to animate], imagery Courtesy JMA

Himawari-8 Water Vapor (6.2 µm) infrared Imagery [click to animate], imagery Courtesy JMA

Tropical Storm Pali has formed in the central Pacific, in a region east-southeast of Kwajalein Atoll (which atoll is at 9 N, 168 E), just west of warm Sea Surface Temperature anomalies (Source) associated with the ongoing El Nino. For the Central Pacific basin, Pali set new records for being the earliest-forming tropical cyclone on record (21 UTC on 7 January), as well as the most Equatorward-forming (at 4.7º N). The Himawari animation, above, of the 6.2 µm Water Vapor imagery from 0000 UTC on 7 January through 1500 UTC 8 January 2016 (mp4 available here), shows impressive upper-level outflow from the region of convection surrounding the storm center. A longer animation of Himawari 10.4 µm Infrared imagery (from 0000 UTC 06 January to 0650 UTC on 8 January) is available here. The Composite Infrared Imagery from AWIPS II, below, shows the slow but steady organization of the storm. Infrared brightness temperatures are very cold, with temperatures occasionally colder than -95º C.

Composite Infrared Imagery (10.7 µm) 0600 UTC 6 January 2016 - 1500 UTC on 8 January 2016 [click to animate]

Composite Infrared Imagery (10.7 µm) 0600 UTC 6 January 2016 – 1500 UTC on 8 January 2016 [click to animate]

Pali is forming in a region that allows views from both GOES-15 (overhead at the Equator and 135º W) and Himawari-8 (overhead at the Equator and 140º E). The Infrared animation below shows GOES-15 at Full Resolution from the Full Disk Imagery that is used to view Pali. Note that Himawari data has been degraded both spatially and temporally in the animation (to match that of GOES).

GOES-15 Infrared Imagery (10.7 µm) (left) and Himawari-8 Infrared (right) (10.35) at full GOES Resolution 0600 UTC 8 January 2016 - 1800 UTC 8 January 2016 [click to animate]

GOES-15 Infrared Imagery (10.7 µm) (left) and Himawari-8 Infrared (right) (10.35) at full GOES Resolution 0600 UTC 8 January 2016 – 1800 UTC 8 January 2016 [click to animate]

An animation that is at full resolution for Himawari-8, for just 3 hours, from 0600-0900 UTC, is below. Only two GOES-15 Images are available during this time period that includes 19 Himawari-8 images. (Note also the increase in spatial resolution with Himawari, from 4 km for GOES to 2 km for Himawari) There is considerable evolution to the storm during these three hours that present-day GOES cannot view because of limited scanning capabilities. GOES-R will provide spatial resolution and image scan rates identical to Himawari-8 so meteorologists will be better able to monitor storm evolution.

GOES-15 Infrared Imagery (10.7 µm) (left) and Himawari-8 Infrared (right) (10.35) at full Himawari-8 Resolution 0600 UTC 8 January 2016 - 0900 UTC 8 January 2016 [click to animate]

GOES-15 Infrared Imagery (10.7 µm) (left) and Himawari-8 Infrared (right) (10.35) at full Himawari-8 Resolution 0600 UTC 8 January 2016 – 0900 UTC 8 January 2016 [click to animate]

Himawari True-Color Imagery, below, shows both Pali, a large relatively disorganized system in the central north Pacific and Cyclone Ula, a compact and more organized system in the tropical south Pacific. Himawari True-Color (actually a 4-banded composite meant to emulate True Color) imagery is routinely available here.

Himawari-8 True-Color Visible Imagery [click to enlarge], imagery Courtesy JMA

Himawari-8 True-Color Visible Imagery [click to enlarge], imagery Courtesy JMA

Typhoon In-fa

November 20th, 2015

MTSAT-2 Infrared (10.8 µm) image with the track of In-fa [click to enlarge]

MTSAT-2 Infrared (10.8 µm) image with the track of In-fa [click to enlarge]

Tropical Depression In-fa (27W) formed well south of the Marshall Islands in the West Pacific Ocean on 17 November 2015, and proceeded to track northwestward to a position south of Guam on 20 November (above). Following a brief decrease in intensity on 18 September, In-fa began another period of intensification during the 19-20 September period. Rapid-scan (2.5-minute interval) Himawari-8 Visible (0.64 µm) images (below; also available as a large 73 Mbyte animated gif) showed a series of eyewall convective bursts and the occasional appearance of a recognizable eye. (Note: the ABI instrument on the upcoming GOES-R satellite will also have a rapid-scan capability, but at 1-minute or even 30-second intervals)

Himawari-8 Visible (0.64 um) images [click to play MP4 animation]

Himawari-8 Visible (0.64 um) images [click to play MP4 animation]

A longer animation spanning the entire 19-20 September period (below; also available as a large 120 Mbyte animated gif) revealed an improving trend in the overall satellite presentation of In-fa, with the eye becoming well defined by the end of the animation as the tropical cyclone reached Category 3 intensity.  In fact, this became the the 15th Category 3 or stronger typhoon in the Northwest Pacific basin in 2015 – the most on record in any tropical cyclone season by the date of 20 November.

Himawari-8 Infrared (10.4 um) images [click to play MP4 animation]

Himawari-8 Infrared (10.4 um) images [click to play MP4 animation]

A comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 1547 UTC (below; courtesy of William Straka, SSEC) showed the coldest cloud-top IR brightness temperatures in the southern hemisphere of the eyewall, along with the nighttime glow of lights from the island of Guam.

Suomi NPP VIIRS Infrared (11.45 um) and Day/Night Band (0.7 um) images [click to enlarge]

Suomi NPP VIIRS Infrared (11.45 um) and Day/Night Band (0.7 um) images [click to enlarge]

A well-defined eye was evident in MTSAT-2 Infrared (10.8 µm) and DMSP SSMIS Microwave (85 GHz) images around 2230 UTC on 20 September (below).

DMSP-19 SSMIS microwave (85 GHz) and MTSAT Infrared (10.8 um) images [click to enlarge]

DMSP-19 SSMIS microwave (85 GHz) and MTSAT Infrared (10.8 um) images [click to enlarge]

Mesovortices within the eye were seen in rapid-scan Himawari-8 Visible (0.64 µm) images beginning late in the day on 20 November as In-fa intensified to a Category 4 typhoon. (below;  also available as a large 50 Mbyte animated GIF).

Himawari-8 Visible (0.64 µm) images [click to play MP4 animation]

Himawari-8 Visible (0.64 µm) images [click to play MP4 animation]

Hurricane Kate

November 10th, 2015

GOES-13 Visible (0.65 µm) imagery (Click to animate) (Click to enlarge)

GOES-13 Visible Imagery, above, shows Tropical Storm Kate northeast of the Bahamas late in the day on 9 November. The storm is over a region of warm sea surface temperatures, below (imagery from the CIMSS Tropical Weather Site), in an environment of low shear. RapidScat winds show winds between 35 and 40 knots to the northeast of the storm center. The projected path is also shown, paralleling the East Coast before moving out to sea. The path takes the storm north of Bermuda as well.

Sea-surface Temperatures, Wind Shear, and near-surface Winds, 9 November 2015 (Click to enlarge)

Suomi NPP viewed the storm as well, shortly after noon on 9 November. The Visible (0.64 µm), near-infrared (1.61 µm) and 11.35 µm imagery are shown below. The 1.61 imagery shows darker returns over ice clouds because of absorption at that wavelength. The extensive cirrus shield over Kate’s convection (and along the East Coast is association with frontal system) is readily apparent. Water-based clouds, in contrast, are bright white in both the visible and near-infrared channels.

Suomi NPP Visible (0.64 µm), near-infrared (1.61 µm) and infrared (11.45 µm) at 1836 UTC, 9 November 2015 (Click to enlarge) (Click to enlarge)

ASCAT winds from 0230 UTC on 10 November (below) also show strongest winds on the northern and eastern sides of the storm.

METOP Scatterometer winds and GOES-13 Infrared (10.7 µm) at 0230 UTC 10 November 2015 (Click to enlarge)

Kate was upgraded to a minimal Hurricane at 0900 UTC on 11 November.