Two Tropical Storms in the Pacific

June 30th, 2014
GOES-15 0.62 µm visible channel images (click to play animation)

GOES-15 0.62 µm visible channel images (click to play animation)

Tropical Storms Douglas (center of the image) and Elida (right-hand side of the image) have formed in the tropical Pacific to the west of Mexico. From the animation above (click here for an animation of the 10.7 µm imagery), Elida is in an environment of northerly/northwesterly shear: the strongest convection is forming south of the low-level circulation. This should in the short term inhibit significant strengthening. Douglas is moving into a region of cooler Sea-surface temperatures and is therefore weakening (SST imagery was captured here). Note, for example, how strong convection is not forming in the center of Douglas’ circulation.

One observation that can be related to the vigor of a tropical cyclone is the number of overshooting tops (OTs) within the storm circulation. This website displays OTs for any active storm. The still image below shows the OTs detected over Douglas and Elida at 2130 UTC on 30 June. It is uncommon for a storm to weaken significantly in the short term when OTs persist. There are more OTs over Elida than over Douglas in this image. Here are time series for the number of OTs with Douglas and with Elida.

GOES-15 0.62 µm visible channel images (click to enlarge)

GOES-15 Automated Overshooting Tops detected over the eastern Pacific (click to enlarge)

40 years of Satellite Imagery

June 27th, 2014
Synchronous Meteorological Satellite (SMS-1) 11 µm infrared channel image, 2130 UTC 27 June 1974 (click to enlarge)

Synchronous Meteorological Satellite (SMS-1) 11 µm infrared channel image, 2130 UTC 27 June 1974 (click to enlarge)

The oldest satellite image in the SSEC data archive is shown above, taken 40 years ago on 27 June 1974, from SMS-1 (the corresponding visible image can be seen here). The infrared channel sensed radiation in a broad spectrum between 10.5 and 12.6 µm (source). The SMS-1 satellite (launched on 17 May 1974) was positioned over the Equator over eastern South America, at about 45 degrees West Longitude.

More information on the SSEC Datacenter archive is here.

Saharan Air Layer dust over the Gulf of Mexico

June 21st, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data on 20 June 2014 (above; click image to play animation; also available as an MP4 movie file) and on 21 June 2014 (below; click image to play animation; also available as an MP4 animation file) revealed the hazy signature of a veil of Saharan Air Layer (SAL) dust aloft over much of the southern and western portions of the Gulf of Mexico.

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

The hazy dust signature also showed up well in Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images, as visualized using the SSEC RealEarth web map server (below).

Suomi NPP VIIRS true-color RGB images

Suomi NPP VIIRS true-color RGB images

The SAL tracking product showed the strong pulse of SAL dust emerging from the African continent on 10 June, then moving rapidly westward across the Atlantic Ocean and over the Caribbean Sea by 17 June (below; click image to play animation).

Meteosat-10 Saharan Air Layer tracking product (click to play animation)

Meteosat-10 Saharan Air Layer tracking product (click to play animation)

Thunderstorms over the interior of Alaska

June 19th, 2014
Suomi NPP VIIRS 0.64 µm visible channel images, with contours of GFS90 500 hPa geopotential height

Suomi NPP VIIRS 0.64 µm visible channel images, with contours of GFS90 500 hPa geopotential height

AWIPS images of Suomi NPP VIIRS 0.64 µm  visible channel data (above) showed the development of early afternoon thunderstorms over the interior of Alaska as an upper-level low moved westward over the region on 19 June 2014.

An animation of VIIRS 11.45 µm IR channel images spanning the 18-19 June period (below) depicted large areas of cloudiness exhibiting cold cloud-top IR brightness temperature values in the -45 to -50º C range (darker red color enhancement). During this time some locations across the interior of Alaska received over 4 inches of rainfall, prompting the issuance of Flood Warnings for parts of the Goodpaster, Salcha, and Upper Chena Rivers.

Suomi NPP VIIRS 11.45 µm IR channel images

Suomi NPP VIIRS 11.45 µm IR channel images

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Blended Total Precipitable Water product (click to play animation)

Blended Total Precipitable Water product (click to play animation)

The Blended Total Precipitable Water (TPW) product (above; click image to play animation) showed areas where TPW values were in the 25-30 mm or 1.0 to 1.2 inch range (darker green to yellow color enhancement). The corresponding Percent of Normal TPW product (below; click image to play animation) indicated that these TPW values were generally in the 150-200% of normal range for this region and this time of year.

Percent of Normal Blended Total Precipitable Water product (click to play animation)

Percent of Normal Blended Total Precipitable Water product (click to play animation)