Ice floes off the coast of Labrador and Newfoundland

July 2nd, 2016

Inspired by this as seen on Twitter:


we decided to take a look at some satellite imagery. GOES-13 (GOES-East) Visible (0.63 µm) images (below) captured the fluid motion of ice floes off the coast of Labrador and Newfoundland on 02 July 2016.

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

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

A comparison of Terra MODIS true-color and false-color Red/Green/Blue (RGB) images viewed using RealEarth (below) aided in the discrimination of cloud vs ice/snow — in the false-color images, snow/ice appeared as shades of cyan, in contrast to supercooled water droplet clouds which appeared as shades of white.

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

An alternative RGB image for use in the discrimination of cloud vs snow/ice is shown below; in this particular false-color RGB image, snow/ice features appear as shades of red. Surface observations at the time of the Terra MODIS image are plotted in yellow.

Terra MODIS Visible (0.65 µm) and False-color images [click to enlarge]

Terra MODIS Visible (0.65 µm) and False-color images [click to enlarge]

2 days later, 04 July maps from the Canadian Ice Service (below) indicated that much of these larger ice floes consisted of thick first-year ice with concentrations in the range of 4-6/10ths to 8-10/10ths; the existence of such ice concentration at this particular location was 4-6/10ths to 9-10/10ths above normal.

Ice Concentration and Ice Stage maps for 04 July [click to enlarge]

Ice Concentration and Ice Stage maps for 04 July [click to enlarge]

Ice concentration Departure From Normal [click to enlarge]

Ice concentration Departure From Normal [click to enlarge]

Dry trade wind surge approaches Hawai’i

July 2nd, 2016

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The MIMIC Total Precipitable Water product (above) showed the westward movement of a surge of dry trade winds toward Hawai’i during the 28 June – 01 July 2016 period. This push of dry air was being driven by a large area of high pressure centered about 1200 miles northeast of the island chain. A very sharp gradient in TPW existed along the leading edge of the dry surge, with values of 50-55 mm (2.0-2.2 inches) ahead of the boundary dropping to as low as 20-25 mm (0.8-1.0 inch) behind it.

GOES-15 (GOES-West) Visible (0.63 µm) images (below) revealed a sharp contrast in cloudiness east of Hawai’i on 29 June, with far fewer and much smaller marine boundary layer cloud elements seen in the dry air east of the leading edge of the trade wind surge.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

On the following day (30 June), GOES-15 Visible (0.63 µm) images (below) showed a vast expanse of small closed-cell convective clouds in the marine boundary layer — a signature of a stable air mass; in this case, due to strong low-level subsidence — extending to distances as far as 1000 miles east and northeast of Hawai’i.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

The progression of the leading edge of the dry trade wind surge could also be followed on daily composites of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 26-30 June, as viewed using RealEarth (below).

Suomi NPP VIIRS true-color composite images [click to play animation]

Suomi NPP VIIRS true-color composite images [click to play animation]

Skew-T diagrams of rawinsonde data from the 2 upper air sites in Hawai’i (Hilo PHTO, and Lihue PHLI) are shown below. At Hilo on the Big Island of Hawai’i, the height of the trade wind temperature inversion descended from the typical height of 5500-6000 feet (near the 850 hPa pressure level) on 30 June to an unusually-low height of around 2500 feet (near the 930 hPa pressure level) at 12 UTC on 01 July. Farther to the west at Lihue on the island of Kaua’i, the dry trade wind surge was just beginning to arrive around the time of the 12 UTC sounding on 01 July — a sharpening of and a slight lowering of the trade wind inversion could be seen in comparison to the earlier 00 UTC sounding.

Hilo, Hawai'i rawinsonde reports [click to enlarge]

Hilo, Hawai’i rawinsonde reports [click to enlarge]

Lihue, Hawai'i rawinsonde data [click to enlarge]

Lihue, Hawai’i rawinsonde data [click to enlarge]

As the strong trade wind flow interacted with the terrain of the islands, areas of high wind gusts were observed — for example, 36 knots (41 mph) at Bradshaw Army Air Field on the Big Island of Hawai’i. In addition, the dew point temperature at that site was as low as 21º F within an hour after that peak wind gust on the afternoon of 01 July.

Gypsy moth defoliation in parts of New England

June 26th, 2016

Props to the Boston/Taunton National Weather Service forecast office for sending out the following on Twitter:

Terra MODIS true-color images from 25 May and 26 June 2016 [click to enlarge

Terra MODIS true-color images from 25 May and 26 June 2016 [click to enlarge]

Taking a closer look at 250-meter resolution Terra MODIS true-color (Bands 1/4/3) Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above), the loss of “green-ness” due to defoliation of large areas of trees is quite evident — most notably in western Rhode Island, but also across the border into extreme southern Massachusetts and in parts of eastern Connecticut. This defoliation was caused by an infestation of gypsy moth caterpillars (media report 1 | media report 2).

The corresponding Terra MODIS false-color (Bands 7/2/1) RGB images (below) also help to highlight the areas of tree defoliation, as indicated by a decrease in bright green hues.

Terra MODIS false-color images from 25 May and 26 June 2016 [click to enlarge]

Terra MODIS false-color images from 25 May and 26 June 2016 [click to enlarge]

On 25 June, the highly-concentrated area of tree defoliation across northwestern Rhode Island exhibited a low Normalized Difference Vegetation Index (NDVI) of 0.4 to 0.6, compared to other areas in the southern and eastern part of the state where NDVI values were in the 0.7 to 0.8 range (below).

Aqua MODIS Normalized Difference Vegetation Index (NDVI) product [click to enlarge]

Aqua MODIS Normalized Difference Vegetation Index (NDVI) product [click to enlarge]

Much of the affected region was experiencing Abnormally Dry to Moderate Drought conditions, and had only received  between 25-75% of normal precipitation during the preceding 30/60/90-day periods — this created ideal conditions for the hatching of gypsy moth caterpillar eggs. If these dry conditions persist, it will limit the ability of the deciduous trees to recover and begin producing leaves again during the remainder of the summer season.

Deadly tornado in Yancheng, China

June 23rd, 2016

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

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

Himawari-8 AHI Visible (0.64 µm) and Infrared Window (10.4 µm) images (above) showed the east-southeastward propagation of a mesoscale convective system which produced a deadly tornado in Yancheng, China around 2:30 pm local time on 23 June 2016 (Weather Underground blog). The location of Yancheng (33°23?N, 120°7?E) is denoted by the cyan * symbol, and the animation briefly pauses on the 0630 UTC images which match the reported time of the tornado. Overshooting tops are evident on the visible imagery, and cloud-top infrared brightness temperatures of -80º C or colder (violet color enhancement) also appear, even after the storm crossed the coast and moved over the adjacent offshore waters of the Yellow Sea (note: due to parallax, the apparent location of the storm top features is displaced several miles to the north-northwest of their actual position above the surface). The spatial resolutions (0.5 km visible, 2 km infrared) of the AHI images are identical to those of the corresponding spectral bands that will be available from the ABI instrument on GOES-R.

An experimental version of the MIMIC Total Precipitable Water product which uses the MIRS retrieval TPW from POES, Metop, and Suomi NPP VIIRS satellites (below) revealed the band of high moisture pooled along the Mei-yu front, which appeared to surge northward across eastern China early in the day on 23 June.

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The 23 June/00 UTC rawinsonde report from Nanjing (located about 260 km southwest of Yancheng) indicated a total precipitable water value of 66.2 mm or 2.6 inches (below).

Nanjing, China rawinsonde report [click to enlarge]

Nanjing, China rawinsonde report [click to enlarge]