Land breeze convergence cloud band in Lake Michigan

September 23rd, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface and buoy reports [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow cloud band that had developed in Lake Michigan in response to land breeze induced convergence on the morning of 23 September 2018. With inland temperatures cooling overnight into the 30s and 40s F (the coldest in both Wisconsin and Michigan was 29ªF) and lake water temperatures of 64ºF (at the North Michigan buoy 45002) to 69ºF (at the South Michigan buoy 45007), a well-defined nocturnal land breeze was established along the western and eastern shorelines of the lake.

Nighttime VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC (below) showed that the cloud band had not yet formed at those times.

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

The Terra and Aqua MODIS Sea Surface Temperature product (below) confirmed that mid-lake water temperatures were generally in the middle to upper 60s F (green to light yellow enhancement) across the entire length of Lake Michigan.

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

An examination of the MODIS SST product with overlays of RTMA surface winds (below) showed that there was no clear signature in the model wind field of enhanced convergence either before or after the mid-lake cloud band had formed.

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

However, an overpass of the Metop-A satellite at 1559 UTC provided ASCAT surface scatterometer winds that did a better job than the RTMA at highlighting the mid-lake convergence that was helping to sustain the cloud band (below). This example underscores the value that satellite-derived winds can have over even high resolution models.

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Remnants of Post-Tropical Cyclone Florence north of Bermuda

September 20th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of Derived Motions Winds [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images and their Derived Motion Winds (above) revealed the partially exposed low-level circulation associated with the indirect remnants of Post-Tropical Cyclone Florence north of Bermuda on 20 September 2018 (surface analyses). The strongest Visible winds — calculated by tracking cloud features having a height assignment at or below the 700 hPa pressure level — located west and northwest of the circulation center were generally in the 35-40 knot range during the later part of the day, with one target being tacked at 56 knots (though this seemed to be an anomalous outlier).

However, ASCAT scatterometer data from an overpass of the Metop-A satellite at 1335 UTC (below) only sensed surface winds speeds (deduced from ocean surface roughness) as high as 25 knots around the center of the circulation.

Metop-A ASCAT surface scatterometer winds [click to enlarge]

Metop-A ASCAT surface scatterometer winds [click to enlarge]

Using a GOES-16 satellite-winds-derived 850 hPa Relative Vorticity product from the CIMSS Tropical Cyclones site (below), motion of the lower-tropospheric vorticity associated with Florence could be followed from landfall on 14 September to the current position north of Bermuda 6 days later. While the bulk of the vorticity became elongated (as Post-Tropical Cyclone Florence transformed into more of a weak baroclinic frontal wave over the Northeast US on 18 September: surface analyses), a small portion of the remnant 850 hPa vorticity became separated and then moved southeastward across the Atlantic.

GOES-16 Relative Vorticity product [click to play animation | MP4]

GOES-16 Relative Vorticity product [click to play animation | MP4]

Sea Surface Temperature and Ocean Heat Content [click to enlarge]

Sea Surface Temperature and Ocean Heat Content [click to enlarge]

A tropical Invest (98L) was initiated by the National Hurricane Center to gather additional data and more closely monitor this feature. Although the circulation had been moving over the Gulf Stream where warm Sea Surface Temperature and modest Ocean Heat Content existed (above), deep-layer wind shear was increasing over the area due to the approach of a branch of the polar jet stream (below).

GOES-16 Mid-level Water Vapor (6.9 µm) images, with deep-layer wind shear analyzed at 22 UTC [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with deep-layer wind shear analyzed at 22 UTC [click to enlarge]

Although deep convection was displaced to the southeast of the low-level circulation center, the GOES-16 Total Precipitable Water derived product (below) showed that ample moisture remained in place farther to the northwest over the Invest 98L.

GOES-16 Low-level Water Vapor (7.3 µm) images + Total Precipitable Water derived product [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images + Total Precipitable Water derived product [click to play MP4 animation]

===== 21/22 September Update =====

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images (above) showed the cyclonic spin of Invest 98L as it moved south of Bermuda on 21 September.

On 22 September, the circulation continued to drift a bit farther south of Bermuda (below), a few hundred miles north of an area of Saharan Air Layer dust (discussed here) — note the hazy signature of the dust on Visible imagery, along with elevated Aerosol Optical Depth values of 0.6 to 0.7 having a good coverage of medium to high confidence Dust Detection.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, along with Aerosol Optical Depth and Dust Detection products [click to play MP4 animation]

Hurricane Florence continues to approach the southeastern US

September 11th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

Hurricane Florence maintained Category 4 intensity on the morning of 11 September 2018 — and 1-minute (initially 30-second, until 1345 UTC) Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) and “Clean” Infrared Window (10.3 µm) images (below) showed improving eye structure after the tropical cyclone completed an eyewall replacement cycle during the preceding nighttime hours (MIMIC TC). A distinct pattern of transverse banding was also evident within the northern semicircle of Florence on Infrared imagery.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

DMSP-18 SSMIS Microwave (85 GHz) imagery from the CIMSS Tropical Cyclones site (below) showed a large eye at 1015 UTC, and also at 1103 UTC.

DMSP-18 SSMIS Microwave (85 GHz) and GOES-16

DMSP-18 SSMIS Microwave (85 GHz) and GOES-16 “Clean” Infrared Window (10.3 µm) images at 1015 UTC [click to enlarge]

GOES-16 Upper-level Water Vapor (6.2 µm) images with Derived Motion Winds (below) revealed that a well-defined high altitude outflow channel had developed northwest of Florence, helping the storm to maintain its intensity.

GOES-16 Upper-level Water Vapor (6.2 µm) images, with Derived Motion Winds [click to play MP4 animation]

GOES-16 Upper-level Water Vapor (6.2 µm) images, with Derived Motion Winds [click to play MP4 animation]

1-minute GOES-16 True Color Red-Green-Blue (RGB) images (courtesy of Kathy Strabala, CIMSS; details) are shown below. A larger-scale RGB animation beginning at sunrise is available here (courtesy of Rick Kohrs, SSEC).

GOES-16 natural color RGB images [click to play MP4 animation]

1-minute GOES-16 True Color RGB images, 1330-1440 UTC [click to play MP4 animation]

Taking a closer look at the center of Florence later in the day, 1-minute GOES-16 data (below) showed mesovortices within the eye on Visible imagery, along with a narrow radial band of colder (darker red) cloud-top infrared brightness temperatures about 30-50 miles from the inner edge of the eyewall.

GOES-16

GOES-16 “Red” Viisible (0.64 µm) images [click to play MP4 animation]

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

===== 12 September Update =====

Florence remained at Category 4 intensity early in the day as it continued its northwestward motion toward the southeast coast of the US on 12 September. A 20-hour period of 1-minute GOES-16 Infrared images (from 0000-2015 UTC) is shown below.

1-minute GOES-16

1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images, from 0000-2015 UTC [click to play MP4 animation]

Nighttime toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 are shown below (courtesy of William Straka, CIMSS). Bright lightning-illuminated cloud areas can be seen on the DNB images distant to the north and northwest of the storm center; with minimal illumination from the Moon (which was in the Waxing Crescent phase, at only 10% of Full), Florence was illuminated primarily via airglow. On the Infrared images, a coarse pattern of transverse banding was evident along the far southern and western periphery of the storm.

Suomi NPP VIIRS Day/Night Band and Infrared Window images [click to enlarge]

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

NOAA-20 VIIRS Day/Night Band and Infrared Window images [click to enlarge]

NOOA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A sequence of Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images (below) showed dramatic changes in the cold central dense overcast (CDO) of Florence between 02 and 18 UTC.

Infrared Window images from Terra MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

Infrared Window images from Terra MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

During the morning hours, 1-minute GOES-16 Visible and Infrared images (below) once again displayed a distinct eye and eyewall structure, with surface mesovortices evident within the eye. A curious linear standing wave — extending radially outward to the northeast of the storm center — developed from about 13-15 UTC (best seen on Infrared images).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

ASCAT surface scatterometer winds from Metop-A (below) were as strong as 76 knots just northeast of the eye at 1450 UTC.

GOES-16

GOES-16 “Red” Visible (0.64 µm) image with Metop-A ASCAT surface scatterometer winds [click to enlarge]

A stereoscopic animation using GOES-16 and GOES-17 imagery is shown below — to view in three dimensions, cross your eyes until 3 equal images are apparent, then focus on the image in the center. *Note: GOES-17 images shown here are preliminary and non-operational*

Stereoscopic animation using GOES-16 and GOES-17

Stereoscopic animation using GOES-16 and GOES-17 “Red” Visible (0.64 µm) imagery [click to play animation]

During the afternoon hours, GOES-16 Visible and Infrared images (below) showed that the eye presentation  was beginning to deteriorate as Florence weakened to Category 3 intensity by 21 UTC.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

GOES-16

GOES-16 “Clean” Infrared Window {10.3 µm) images [click to play MP4 animation]

The MIMIC Total Precipitable Water product (below) indicated that high TPW values associated with Florence began to move inland along the US East Coast by the end of the day.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

Tropical Storm Gordon

September 3rd, 2018 |

NOAA-20 Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0636 UTC [click to enlarge]

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

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0726 UTC [click to enlarge]

Potential Tropical Cyclone 7 was located between the Bahamas and Florida during the pre-sunrise hours on 03 September 2018. Toggles between VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from NOAA-20 at 0636 UTC and Suomi NPP at 0726 UTC are shown above (courtesy of William Straka, CIMSS).

The storm became better organized and increased in intensity, and was named Tropical Storm Gordon at 1205 UTC. Animations of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) (below) showed Gordon as it moved across far southern Florida (where heavy rain and flash flooding occurred) and into the Gulf of Mexico during the daytime hours.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

===== 04 September Update =====

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (above) and “Clean” Infrared Window (10.3 µm) images (below) showed a series of widespread deep convective bursts within the northeast quadrant of the storm as it moved northeastward toward the Gulf Coast.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

The GOES-16 Rainfall Rate/QPE product (below) indicated rainfall rates of 2-3 inches per hour were possible from this convection, peaking in the 3-4 inch per hour range just after 1300 UTC. However, Infrared cloud-top brightness temperatures warmed dramatically as the convection moved onshore after about 22 UTC — and the Rain Rate product responded accordingly, with a significant decrease in hourly intensity.

GOES-16 Rain Rate product [click to play MP4 animation]

GOES-16 Rain Rate product [click to play MP4 animation]

Metop-A ASCAT surface scatterometer winds of 39 knots were sampled just northeast of the storm center at 1616  UTC (below).

GOES-16 Rain Rate product with Metop ASCAT winds [click to enlarge]

GOES-16 Rain Rate product with Metop-A ASCAT winds [click to enlarge]