Late-season Tropical Storm Otto in the southwest Caribbean Sea

November 21st, 2016
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Metop-A Scatterometer winds at 1430 UTC and GOES-13 10.7 µm Brightness Temperature (Click to enlarge)

A late-season tropical depression has formed in the southwestern Caribbean Sea. The morning Metop-A pass on 21 November 2016 allowed ASCAT scatterometer winds to be sampled over the system: rain-flagged values near tropical storm force were present as shown above. A similar image (from this site) is available here, and also here (from this site).

GOES-13 Infrared (10.7 µm) Brightness Temperatures (Click to animate)

Infrared (10.7 µm) imagery from GOES-13, above, from 1315 through 1715 UTC on 21 November, shows periodic deep convection over the Depression; the grey regions in the deepest convection over the system correspond to brightness temperatures colder than -75 C. The environment surrounding this system, shown below, is marginally favorable for strengthening; sea-surface temperatures are warm, although the oceanic heat content suggests the warmth does not extend through a deep column of water. Wind shear over the storm is modest (but far stronger north of the storm). (Imagery below is from this site). The system is forecast to become a tropical storm within the next 24 hours.

Sea-surface temperatures, Oceanic Heat Content and Wind Shear (Click to enlarge)

Update: Otto was named a tropical storm at 2100 UTC 21 November; GOES-13 Visible (0.63 µm) Imagery is shown below. Numerous tropical overshooting tops can be seen during the course of the day.

GOES-13 Visible (0.63 µm) Imagery on 21 November 2016 (Click to animate)

MIMIC Total Precipitable Water fields, below, show that Otto emerged from a region of persistent deep moisture over the southwestern Caribbean Sea that has been contracting as the storm formed. This region of moisture was focused along the intersection of a stalled and decaying Atlantic frontal zone and the Pacific monsoon trough (hourly animation).

MIMIC Total Precipitable Water fields at 2100 UTC on 17,18,19,20 and 21 November (Click to enlarge)

DMSP-16 Microwave (85 GHz) imagery, below, showed evidence of a closed eye associated with Otto at 2132 UTC.

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) image [click to enlarge]

“Medicane” in the Mediterranean Sea

October 31st, 2016

EUMETSAT Meteosat-10 Infrared Window (10.8 um) images [click to play MP4 animation]

EUMETSAT Meteosat-10 Infrared Window (10.8 um) images [click to play MP4 animation]

A compact tropical-like cyclone (often referred to as a “medicane“) moved across the Mediterranean Sea during the 28-31 October 2016 period. EUMETSAT Meteosat-10 Infrared Window (10.8 um) images (above; also available as a 71 Mbyte animated GIF) showed the system as it developed over the Ionian Sea between Italy and Greece, initially moved southwestward, and then turned to the east where it eventually passed near the Greek island of Crete on 31 October (producing a wind gust to 52 knots at Chania’s Souda Airport LGSA and causing some wind and water damage: media story 1 | media story 2). In addition, a wind gust to 50 knots was seen on a ship report at 12 UTC on 28 October, just to the west of the storm center.

The corresponding EUMETSAT Meteosat-10 Visible (0.64 um) images (below; also available as a 17 Mbyte animated GIF) provided a more detailed look at the structure of the storm during the daylight hours of those 4 days.

EUMETSAT Meteosat-10 Visible (0.64um) images [click to play MP4 animation]

EUMETSAT Meteosat-10 Visible (0.64um) images [click to play MP4 animation]

Daily snapshots of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images viewed using RealEarth are shown below. The hazy signature of blowing dust/sand from northern Africa could be seen within the broad southeast quadrant of the storm circulation.

Suomi NPP VIIRS true-color images [click to enlarge]

Suomi NPP VIIRS true-color images [click to enlarge]

There was ample moisture available to fuel convection around the storm, as seen in the MIMIC Total Precipitable Water product (below).

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The surface wind circulation of the medicane was well-sampled on a variety of Metop-A and Metop-B overpasses, using ASCAT plots (below) from this site.

Metop-A and Metop-B ASCAT surface scatterometer winds, 28-31 October [click to play animation]

Metop-A and Metop-B ASCAT surface scatterometer winds, 28-31 October [click to play animation]

Suomi NPP ATMS images (below; courtesy of Derrick Herndon, CIMSS) revealed the areal coverage of the small “warm core” on Channel 8 (54.94 GHz) and Channel 7 (53.596 GHz); a north-to-south oriented vertical cross section showed the depth of the thermal anomaly associated with the medicane.

Suomi NPP ATMS Channel 8 (54.94 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 8 (54.94 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 7 (53.596 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 7 (53.596 GHz) image, 31 October at 0037 UTC [click to enlarge]

 

North-to-south vertical cross section of Suomi NPP ATMS brightness temperature anomaly [click to enlarge]

North-to-south vertical cross section of Suomi NPP ATMS brightness temperature anomaly [click to enlarge]

For additional information, see this blog post from the Capital Weather Gang.

 

Hurricane Matthew moves into the Bahamas

October 5th, 2016
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Morphed Microwave Imagery showing the eye of Matthew from 1400 UTC 3 October through 1345 UTC 5 October (Click to enlarge)

The animation of Matthew, above, from morphed microwave imagery (from this site), shows the toll that interaction with the high terrain of Hispaniola and eastern Cuba has had on the storm (causing it to be downgraded from Category 4 to Category 3 intensity). The formerly distinct eye had eroded, although eye re-formation occurs at the end of the animation. Once again, a comparison of microwave vs infrared imagery revealed that the well-defined eye structure was much more apparent using microwave data. Strengthening/Re-organization of Matthew in the near term will be governed by Sea Surface Temperatures (that are warm) and wind shear (shown below, from this site, that is weak).

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Diagnosed wind shear, 0900 UTC on 5 October 2016 (Click to enlarge)

Total Precipitable Water fields (from this site, using data from here), below, show abundant moisture surrounding Matthew at its present position. There is dry air over the eastern United States landmass, however.

Morphed Total Precipitable water from MIRS, 1300 UTC 4 October – 1200 UTC 5 October (Click to enlarge)

Morphed Total Precipitable water from MIRS, 1300 UTC 4 October – 1200 UTC 5 October (Click to enlarge)

During the morning and afternoon hours, the satellite presentation of Matthew began to slowly improve on GOES-13 Visible (0.63 µm) and Infrared Window (10.7 µm) imagery, below (MP4 | animated GIF), with well-defined convective bursts seen later in the day. Note: the noise seen on the 1645 UTC images was due to solar RFI.

GOES-13 0.63 µm Visible (left) and 10.7 µm Infrared Window (right) images [Click to play animation]

GOES-13 0.63 µm Visible (left) and 10.7 µm Infrared Window (right) images [Click to play animation]

Hurricane Matthew makes landfall in western Haiti, then eastern Cuba

October 4th, 2016

GOES-13 Visible (0.63 µm) Imagery, 1045-1245 UTC on 4 October 2016 (Click to enlarge)

Hurricane Matthew has made landfall in western Haiti. The rocking animation (click here for a straight animation) above shows the cloud-filled eye of the storm crossing the Tiburon Peninsula. The storm’s center is forecast to remain largely over water as it moves through the Windward Passage between Cuba and Hispaniola.

A closer look using a 2-panel comparison of GOES-13 Visible (0.63  µm) and Infrared Window (10.7 µm) images, below, shows the deteriorating satellite presentation following interaction with the topography of the islands. The GOES-13 satellite was in Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-7 minutes.

GOES-13 0.63 µm Visible (left) and 10.7 µm Infrared Window (right) images [Click to play animation]

GOES-13 0.63 µm Visible (left) and 10.7 µm Infrared Window (right) images [Click to play animation]

NOAA-18 overflew the region around 1130 UTC while the eye was on land, and the toggle below shows Visible (0.64 µm) and Infrared Window Channel (10.8 µm) imagery from 1130 UTC. The cloud-filled eye is distinct in the infrared image at that time, but a sequence of POES AVHRR Infrared (12.0 µm) images showed the rapid deterioration shortly after landfall (as was seen in the GOES-13 images above).

NOAA-18 AVHRR Visible (0.64 µm) and Infrared (10.8 µm) Imagery, 1130 UTC on 4 October 2016 (Click to enlarge)

A toggle between 1215 UTC GOES-13 Infrared Window (10.7 µm) and 1217 UTC DMSP-18 SSMIS Microwave (85 GHz) images from the CIMSS Tropical Cyclones site, below, revealed that a well-defined eye was still evident in the microwave data.

GOES-13 Infrared Window (10.7 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [Click to enlarge]

GOES-13 Infrared Window (10.7 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [Click to enlarge]

Aqua overflew Matthew shortly after 1800 UTC on 4 October, and the toggle below shows the 1-km visible (0.65 µm) and the 1-km ‘Cirrus Channel’ (1.38 µm). The Cirrus Channel detects radiation at a wavelength where very strong absorption by water vapor is occurring; only high clouds are detected with this channel, and the toggle between the Cirrus Channel and the Visible nicely outlines the cirrus canopy of the storm. The Advanced Baseline Imager (ABI) on GOES-R also includes a Cirrus Channel.

Aqua MODIS Visible (0.65 µm) and

Aqua MODIS Visible (0.65 µm) and “Cirrus Channel” (1.38 µm) at 1832 UTC on 4 October 2016 [Click to enlarge]

Meanwhile, to the northeast of Matthew, in the tropical Atlantic, Tropical Storm Nicole has formed. The animation of visible imagery from GOES-13, below, shows a sheared storm; the low-level circulation is west of the deepest convection. It’s unlikely that Nicole will intensify much under such sheared conditions. Cirrus outflow from Matthew is evident at the south and west of Nicole.

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

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

ASCAT on METOP-A sampled both storms in its morning overpass over the western Atlantic, as shown below. The maximum scatterometer-derived wind speeds were 60 knots with Matthew and 40 knots for Julia.

GOES-13 Visible (0.63 µm) image, with Metop-AASCAT winds [Click to enlarge]

GOES-13 Visible (0.63 µm) image, with Metop-AASCAT winds [Click to enlarge]

Late in the day on 04 October, Category 4 Hurricane Mathew made a second landfall along the far eastern tip of Cuba. As seen in the image toggle below, in spite of a ragged appearance on GOES-13  Infrared Window (10.7 µm) imagery, a distinct eye was still seen using DMSP-18 SSMIS Microwave (85 GHz) data.

GOES-13 Infrared Window (10.7 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [Click to enlarge]

GOES-13 Infrared Window (10.7 µm) and DMSP-18 SSMIS Microwave (85 GHz) images [Click to enlarge]