Hurricane Earl makes landfall in Belize

August 4th, 2016
GOES-14 10.7 µm Infrared Window images, hourly from 0115 through 1015 UTC on 4 August 2016 [click to play animation]

GOES-14 10.7 µm Infrared Window images, hourly from 0115 through 1015 UTC on 4 August 2016 [click to play animation]

Hurricane Earl made landfall around 0600 UTC on 4 August in Belize. The hourly animation from GOES-14, above, shows a rapid warming of the coldest cloud tops over Earl after landfall, as commonly happens. GOES-14 is out of storage to support SRSO-R Operations beginning Tuesday August 9.

The GOES-14 image at landfall shows coldest cloud tops on the north side of the storm. A timely Metop-A overpass (times available at this site) from several hours before landfall provided ASCAT winds, below, that also show strongest winds to the north side of this storm.

Metop-A ASCAT Scatterometer Winds, 0238 UTC 4 August 2016 [click to enlarge]

Metop-A ASCAT Scatterometer Winds, 0238 UTC 4 August 2016 [click to click to enlarge]

Although the strong winds of Earl have diminished now that the storm is over land, Total Precipitable Water values, below, (showing MIRS data, available at this site) remain high and flooding continues to be a threat. Earl is forecast to move along the southern tip of the Bay Campeche starting tomorrow. For more details see the National Hurricane Center website.

Morphed MIRS Total Precipitable Water, 0600 UTC on 4 August 2016 [click to enlarge]

Morphed MIRS Total Precipitable Water, 0600 UTC on 4 August 2016 [click to click to enlarge]

Three geostationary satellites viewed Earl as it moved across the southern Yucatan peninsula. GOES-15, GOES-14 and GOES-13 visible imagery from near 1200 UTC is shown below.

GOES-15, GOES-14, GOES-13 (left, center,right) Visible Imagery of Earl over Belize and Mexico, ~1200 UTC on 4 August 2016 [click to enlarge]

GOES-15, GOES-14, GOES-13 (left, center,right) Visible Imagery of Earl over Belize and Mexico, ~1200 UTC on 4 August 2016 [click to click to enlarge]

Two Geostationary Satellites viewing a system approximately equidistant from both satellites allowed for stereoscopic imagery to be created, below.

GOES-13 and GOES-14 Visible Imagery (0.62 µm), 1415 - 2115 UTC on 4 August 2016 [click to play animation]

GOES-13 and GOES-14 Visible Imagery (0.62 µm), 1415 – 2115 UTC on 4 August 2016 [click to play animation]

Super Typhoon Nepartak

July 7th, 2016

Track of Super Typhoon Nepartak (03 to 07 July 2016) [click to enlarge]

Track of Super Typhoon Nepartak (03 to 07 July 2016) [click to enlarge]

Super Typhoon Nepartak (02W) formed as a tropical depression in the West Pacific Ocean south of Guam on 02-03 July 2016, and tracked northwestward until making landfall in southern Taiwan on 07 July (above). Nepartak rapidly intensified to a Category 4 storm on 05 July, peaking at Category 5 intensity on 06 July (ADT | SATCON wind | SATCON pressure). Two factors helping the storm to reach and maintain Category 5 intensity for a relatively long period of time were (1) the passage over water having large Ocean Heat Content and Sea Surface Temperature values, and (2) an environment characterized by low deep-layer wind shear (06 July/15 UTC | 07 July/21 UTC).

2.5-minute interval rapid-scan Himawari-8 Infrared Window (10.4 µm) images (below) showed the formation of a well-defined eye with an annular storm structure early in the day on 07 July. The eye became less organized as Nepartak approached the island of Taiwan and made landfall as a Category 4 typhoon around 2150 UTC.

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

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

Surface observations (plot | text) from Feng Nin airport (station identifier RCFN) in Taitung City showed sustained winds of 70 knots (81 mph) with a gust to 99 knots (114 mph) from the north-northeast at 21 UTC, and a pressure of 964.0 hPa (27.47″). iCyclone chaser Josh Morgerman recorded a minimum pressure of 957.7 hPa at 2043 UTC (4:43 am local time) in Taitung City:


Shortly before landfall, a comparison of DMSP-18 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images around 20 UTC (below) showed that the eye was still rather distinct on the microwave image.

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

However, the MIMIC-TC product (below) revealed how quickly the eyewall structure eroded once the circulation of Nepartak encountered the rugged terrain of Taiwan.
MIMIC-TC product [click to enlarge]

MIMIC-TC product [click to enlarge]

Looking back to earlier periods in the storm history, a 2-panel comparison of Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images from 06-07 July (below) revealed the presence of mesovortices within the eye on the visible imagery. The spatial resolution of these Visible (0.5 km) and Infrared (2 km) AHI images is identical to what will be provided by the ABI instrument on GOES-R.
Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play MP4 animation]

Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play MP4 animation]

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from 07 July (viewed using RealEarth) is shown below; the actual satellite overpass time for this image was around 0444 UTC.
Suomi NPP VIIRS true-color image on 07 July [click to enlarge]

Suomi NPP VIIRS true-color image on 07 July [click to enlarge]

During the period of rapid intensification on 06 July, 2.5-minute interval rapid-scan Himawari-8 Infrared Window (10.4 µm) images (below) revealed pulses of storm-top gravity waves which were propagating radially outward away from the eye of Nepartak (especially evident during the later half of the animation period).
Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

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

It is also interesting to note that nighttime mesospheric gravity waves could be seen propagating away from the eye/eyewall region of Nepartak at 1729 UTC or 1:29 am local time on a 06 July Suomi NPP VIIRS Day/Night Band (0.7 µm) image (below, courtesy of William Straka, SSEC). Since very little illumination was provided by the Moon (which was in the Waxing Crescent phase, at only 5% of Full), these waves were being illuminated by airglow.
Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

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

The MIMIC-TC product (below) also showed that Nepartak completed an eyewall replacement cycle on 06 July.
MIMIC-TC product [click to enlarge]

MIMIC-TC product [click to enlarge]

Animations of 10-minute interval Himawari-8 Infrared Window (10.4 µm) images spanning nearly the entire life cycle of Nepartak — from a tropical depression south of Guam on 03 July to landfall over mainland China on 08 July — are available as an MP4 movie (139 Mbytes) or an animated GIF (493 Mbytes).

Tropical Storm Colin in the Gulf of Mexico

June 6th, 2016

MIMIC Total Precipitable Water derived from Microwave imagery, 2300 UTC 02 June - 2200 UTC 05 June [click to enlarge]

MIMIC Total Precipitable Water derived from Microwave imagery, 2300 UTC 02 June – 2200 UTC 05 June [click to enlarge]

The 2016 Atlantic Tropical Season’s third named storm has formed in the Gulf of Mexico just north of the Yucatan Peninsula; Colin became the earliest named “C” storm on record for that basin. MIMIC Total Precipitable Water values for the 72 hours ending at 2300 UTC on 5 June 2016, above, show the storm embedded within a deep band of tropical moisture that has surged northward from the Monsoon Trough / Intertropical Convergence Zone into the northwestern Caribbean and southern Gulf of Mexico (MIMIC TPW + surface analyses). Moisture extends northeastward along the projected path of the storm into northern Florida. Extensive rains are likely over the Southeast US as the storm moves north. Total Precipitable Water (TPW) from MIMIC is a simple band difference between two microwave channels; that difference is invalid over land where emissivity is highly variable. However, MIRS data can estimate TPW over land and water, and its distribution over the eastern United States, below, derived from a morphed animation of the observations, gives a better indication of the spread of rich moisture over the southeastern United States. In addition, the Blended TPW Product showed values in excess of 70 mm (2.76 inches) over the Gulf of Mexico, which were in excess of 170% of Normal.

MIRS-based Total Precipitable Water, 2300 UTC 05 June [click to enlarge]

MIRS-based Total Precipitable Water, 2300 UTC 05 June [click to enlarge]

Colin was poised to moved over a region of higher Ocean Heat Content that was located in the eastern Gulf of Mexico, which could help to fuel additional bursts of deep convection similar to that seen on POES AVHRR infrared imagery, below. For more information on Tropical Storm Colin, refer to the CIMSS Tropical Cyclones site and the National Hurricane Center.

POES AVHRR Visible (0.86 µm) and Infrared (12.0 µm) images [click to enlarge]

POES AVHRR Visible (0.86 µm) and Infrared (12.0 µm) images [click to enlarge]

Bonnie

May 29th, 2016

GOES-13 6.5 µm Water Vapor Infrared images [click to play animation]

GOES-13 6.5 µm Water Vapor Infrared images[click to play animation]

Tropical Depression 2 was upgraded to Tropical Storm Bonnie at 2100 UTC on Saturday 28 May, the second named storm of the 2016 Atlantic Season (Hurricane Alex, which formed in January, was the first named storm). The water vapor animation above shows that Bonnie’s initial spin may be traced to a front associated with an occluded system which crawled through the eastern United States, exiting on about 23 May 2016. It’s not uncommon for vorticity associated with extratropical cyclone fronts to sow the seed of a tropical cyclone, especially early (or late) in the season. In this case, the cold front failed to pass Bermuda, and by 27 May, persistent thunderstorms about halfway between Bermuda and the Bahamas suggested tropical cyclogenesis was underway (GOES-13 visible image animations: 26 May | 27 May).

MIMIC Total Precipitable Water derived from Microwave imagery, 1800 UTC 28 May - 1700 UTC 30 May [click to enlarge]

MIMIC Total Precipitable Water derived from Microwave imagery, 1800 UTC 28 May – 1700 UTC 30 May [click to enlarge]

Total Precipitable Water fields from the microwave MIMIC product, above, show the system was embedded deep within tropical moisture (24-26 May animation). Tropical moisture associated with the storm moved up the east coast of the United States into the mid-Atlantic States with local flooding reported. This longer animation (from 21 through 28 May) shows that persistent westward motion of moisture occurred over the tropical Atlantic well in advance of Bonnie’s formation.

Rapidscat Scatterometer Winds, 1012 UTC on 27 May [click to enlarge]

Rapidscat Scatterometer Winds, 1012 UTC on 27 May [click to enlarge]

The tropical wave that produced Bonnie showed a closed circulation as early as 1012 UTC on 27 May according to Rapidscat scatterometer winds, above, and MODIS Sea Surface Temperatures, below, showed very warm water (with SST values of 80º F) over the Gulf Stream.

MODIS-based Sea Surface Temperatures, 1848 UTC on 27 May [click to enlarge]

MODIS-based Sea Surface Temperatures, 1848 UTC on 27 May [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0621 UTC on 27 May 2016 [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0621 UTC on 27 May 2016 [click to enlarge]

Suomi NPP overflew this tropical system at various times during its lifecycle. Shortly after midnight on 27 May 2016, above, strong convection was centered just north of the apparent surface circulation (as inferred by the curved bands of low-level clouds, clouds made visible by moonlight in the night-time VIIRS Day/Night Band visible imagery). Twenty-four hours later, at 0742 UTC on 28 May, below, in a more zoomed-in view, the (then) Tropical Depression Number 2 is supporting strong convection that is obscuring the low-level circulation center.

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0742 UTC on 28 May 2016 [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0742 UTC on 28 May 2016 [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0723 UTC on 29 May 2016 [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0723 UTC on 29 May 2016 [click to enlarge]

Finally, at 0723 UTC on 29 May, (above) after strong wind shear has displaced all convection well north of the center, the low-level circulation of Tropical Storm Bonnie is southeast of the South Carolina Coast. Strong convection is over North Carolina. This shear was noted in the 0300 UTC and 0900 UTC (29 May) Discussions from the National Hurricane Center. The effect of shear is apparent in the two GOES-13 Infrared Images below, from 2045 UTC on 28 May when convection was close to the center, and from 1045 UTC on 29 May, shortly before landfall, when convection was stripped from the center and displaced well to the north.

GOES-13 Infrared (10.7 µm) Imagery at 2045 UTC on 28 May and at 1045 UTC 29 May 2016; the Yellow Arrow points to the low-level circulation center [click to enlarge]

GOES-13 Infrared (10.7 µm) Imagery at 2045 UTC on 28 May and at 1045 UTC 29 May 2016; the Yellow Arrow points to the low-level circulation center [click to enlarge]

Closer views of the sheared system on 28 May can be seen on 1906 UTC VIIRS and 1937 UTC AVHRR Visible and Infrared images, as well as a GOES-13 Visible animation.

===== 01 June Update =====

GOES-13 Visible (0.63 µm) images [click to play MP4 animation]

GOES-13 Visible (0.63 µm) images [click to play MP4 animation]

The remnant circulation of Bonnie moved very slowly northeastward during the 30 May – 01 June period, as seen in GOES-13 Visible (0.63 µm) images covering each of those 3 days (above; also available as a large 95 Mbyte animated GIF). The periodic formation of deep convective clusters continued to produce heavy rainfall over parts of far eastern North and South Carolina.

On the morning of 01 June, an overpass of the Metop-B ASCAT instrument sampled the flow around the low-level circulation center (LLCC) off the coast of North Carolina; several hours later, Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images provided a high-resolution view of the system at 1755 UTC (below). Cloud-top IR brightness temperatures were as cold as -78º C within the small convective cluster located just north of the LLCC.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]