Suomi/NPP 11.35 µm infrared channel, 0717 UTC on 1 July 2014 and NUCAPS sounding locations in green (click to enlarge)

Suomi/NPP overflew the developing tropical depression #1 (now Tropical Storm Arthur) east of Florida early in the morning on July 1st. The CrIS and ATMS instruments on board S/NPP provide data for NUCAPS soundings that are routinely distributed to AWIPS II. The image above is an overlay of the 11.35 µm infrared imagery with the sounding locations plotted as green dots. Seven sounding locations are indicated on the image above (Here is the image without the seven sounding locations) How well do NUCAPS soundings represent the tropical atmosphere that is supporting the development of Arthur?

The 7 soundings indicated in the plot above are: 1 (Just south of Pensacola, FL), 2 (Off the coast of Georgia), 3 (northeast of Arthur in the tropical Atlantic), 4 (Cape Canaveral), 5 (north of Tampa Bay), 6 (the western tip of Cuba) and 7 (northeastern Cuba).

GOES Sounder DPI Total Precipitable Water at 0700 UTC on 1 July 2014 (click to enlarge)

How does Precipitable Water from the NUCAPS soundings compare to observations from other satellite-based systems? GOES Sounder DPI TPW from 0800 UTC shows values around 50 mm over interior the southeast United States, and over the tropical Atlantic to the northeast of the tropical system. A corridor of lower values, around 30-35 mm, extends northeast of Jacksonville, FL. Smaller values (30-40 mm) also extend southeastward from the lower Mississippi River valley into the Gulf of Mexico. A similar pattern in the precipitable water is evident in the blended product, here. Precipitable water values from the NUCAPS soundings appear, for this case, to be too low. The value at Cape Canaveral (point 4), for example, is 1.59″ (40 mm, versus close to 50 mm from the Sounder and the Blended Product); off the coast of Georgia (point 2), 1.30″ (33 mm vs. close to 41 mm from the Sounder and Blended Product); south of Pensacola (point 1), 1.25″ (31 mm vs. 35 mm from the Sounder and the Blended Product); north of Tampa Bay (point 5), 1.46″ (37 mm vs 47 mm from the Sounder and the Blended Product); northeast of the tropical system (point 3), 1.84″ (47 mm vs 49 mm from the Sounder/Blended Product); western Cuba (point 6), 1.70″ (43 mm, similar to the 44 mm from the Sounder/Blended Product); and northeast cuba (point 7), 1.22″ (31 mm vs. 39 from the Sounder and 34 from the Blended Product). The lowest 3 kilometers of the atmosphere (where most of the moisture resides) is the most difficult part for a satellite-based sounding, but there do appear to be differences between the two satellite-based sounding products (GOES and NUCAPS) in this case.

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

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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.

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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)

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

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)

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