NUCAPS soundings near a Tropical Disturbance

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

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)

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.

NUCAPS Soundings available in AWIPS II

June 10th, 2014 |
Suomi/NPP VIIRS 11.45 µm IR channel and NUCAPS sounding points (click to enlarge)

Suomi/NPP VIIRS 11.45 µm IR channel and NUCAPS sounding points (click to enlarge)

NOAA Unique Cross-track Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) Processing System (NUCAPS) Soundings have started flowing into AWIPS-2 at NWS WFOs across the country. These soundings offer high spectral (and high spatial) resolution soundings derived from the CrIS and ATMS instruments that fly on the Suomi/NPP satellite. The toggle above shows the footprint of the soundings in comparison to an 11.45 µm VIIRS instrument (also on the Suomi/NPP satellite) IR image from approximately 1800 UTC on 10 June 2014. The NUCAPS soundings cover a larger area because they are processed by NOAA/NESIS (vs. being downloaded on the X-Band Direct Broadcast antenna at CIMSS in Madison WI, whose antenna is the source of the VIIRS 11.45 µm IR image shown).

The sounding data, if available, are under the ‘Satellite’ menu tab of AWIPS-2, and then NPP Products can be selected to view NUCAPS Sounding Availability, as shown in this screenshot. Once the sounding locations are loaded, the mouse can be used to select a point, and a left click produces a sounding in an NSharpEditor environment; that is, you can edit it (if, for example, you think the surface dewpoint in the sounding is too dry).

The mid-continent overpass at around 1800 UTC can provide valuable information on the possibility of convective development. For example, consider the visible imagery below from 1915 UTC on May 29 2014. Will convection develop out of that broken cumulus field as forecast by the GFS (not shown)?

GOES-13 0.63 µm Visible Imagery, 1915 UTC 29 May 2014 (click to enlarge)

GOES-13 0.63 µm Visible Imagery, 1915 UTC 29 May 2014 (click to enlarge)

The animation below steps through the Suomi/NPP overpass just after 1800 UTC that was used to created NUCAPS soundings on that day, followed by a close-up over Omaha, then a screen-capture of the created sounding. The sounding (which includes surface values close to those reported by the METAR) has only modest values of Convective Available Potential Energy (CAPE), suggesting that convection is unlikely. And, indeed, visible imagery near sunset shows dissipating cumulus clouds.

NUCAPS Sounding over North America, over Omaha and surroundings, and the individual NUCAPS sounding indicated (Courtesy of Dan Nietfeld, SOO at Omaha/Valley WFO, click to enlarge)

NUCAPS Sounding over North America, over Omaha and surroundings, and the individual NUCAPS sounding indicated (Courtesy of Dan Nietfeld, SOO at Omaha/Valley WFO, click to enlarge)

A second case, below, also from Dan Nietfeld, shows NUCAPS soundings before the devastating hailstorm on June 3 in a High Risk region. In this case, the NUCAPS soundings underestimated the temperature/dewpoint at the surface, but the editable sounding software makes quick work of adjusting the lowest part of the sounding, and the CAPE in the adjusted sounding increased from 1800 to more than 3000. (The location of the sounding is shown here; it is the southern of the two circled green dots.) NUCAPS data underscores the potential of any convection.

NUCAPS soundings, original and adjusted, 1849 UTC on 3 June (click to enlarge)

NUCAPS soundings, original and adjusted, 1849 UTC on 3 June (click to enlarge)

(Click here for further information on ATMS; Click here for further information on CrIS). Many thanks to Dan Nietfeld, SOO at Omaha, for imagery above. Hyperspectral Soundings are described in a COMET module that can be viewed here. A paper (pdf format) describing validation of NUCAPS soundings is available here. Suomi/NPP support is provided in part by the NOAA/NESDIS Joint Polar Satellite System (JPSS) program.

Typhoon Soulik in the northwest Pacific Ocean

August 20th, 2018 |

Himawari-8 AHI Band 13 Clean Window (10.4 µm) imagery, 0900-1400 UTC on 18 August 2018 (Click to animate)

Typhoon Soulik, south of Japan and moving westward, has acquired a very large eye — almost 100 miles across! Himawari-8 imagery, above (courtesy JMA), shows the evolution and enlargement of the eye between 0900 and 1400 UTC on 20 August 2018.

GCOM, Suomi NPP and NOAA-20 all passed over Soulik between 1600 and 1715 UTC on 18 August. The Infrared Toggle, below, from NOAA-20 (1608 UTC) and Suomi NPP (1658 UTC) also shows a large eye.

NOAA-20 (1608 UTC) and Suomi NPP (1658 UTC) 11.45 µm Infrared Imagery of Soulik on 18 August 2018 (Click to enlarge)

Day Night Band Imagery from Suomi NPP, below, also shows a large eye. There was little lunar illumination occurring at the time because the moon was below the horizon.

Suomi NPP Day Night Band Visible (0.70 µm) Imagery over Soulik, 1658 UTC on 18 August 2018 (Click to enlarge)

GCOM overflew Soulik at 1702 UTC, and the AMSR-2 instrument on board gave estimates of rain rate, both convective and a the surface. Those are toggled below.

GCOM AMSR-2 Microwave estimates of Precipitation over Soulik, 1702 UTC on 18 August 2018 (Click to enlarge)

(Suomi NPP, NOAA-20 and GCOM imagery courtesy William Straka, CIMSS)

Soulik’s eye was wide enough that a NUCAPS soundings retrieval (Click here for more information on NUCAPS soundings) could be made from data collected during a Suomi-NPP overpass at 0350 UTC on 21 August 2018.  Note the green sounding location within Soulik’s eye — Green dots denote regions where the infrared retrieval was successful.  The sounding at that point is shown below. (NUCAPS imagery courtesy Landon Aydlett, WFO Guam).

Suomi NPP NUCAPS sounding locations at 0350 UTC on 21 August 2018 on top of AHI 10.4 µm Clean Window imagery (Click to enlarge)

Suomi NPP NUCAPS Sounding within the eye of Soulik at 0350 UTC on 21 August 2018 (Click to enlarge)

You can use NUCAPS Soundings to diagnose the difference between the environment in the storm eye, and in the surrounding environment. The animation below shows locations of 5 soundings, one in the Eye, and one north, east, south and west of the CDO.  The five selected soundings are shown at the bottom, with insets showing which sounding is which.  The sounding in the eye shows remarkable warmth, as expected:  at 555 hPa, for example, eye temperatures are around 8º C;  values at the 4 outside points range from 0.4º to 2.9º C.  Sounding parameters as viewed in AWIPS can be seen here.

Suomi NPP NUCAPS Sounding Points overlain on a Day Night Band Image, ~0350 UTC on 21 August 2018 (Click to enlarge). Sounding locations are indicated.

NUCAPS Soundings in and around Typhoon Soulik at the locations indicated, ~0350 UTC on 21 August 2018 (Click to enlarge)

Soulik’s path is projected to remain south of Japan and approach the Korean Peninsula by mid-week. For more information on Soulik, consult the CIMSS/SSEC Tropical Weather Website, or the Joint Typhoon Warning Center.

Tropical Storm Beryl forms in the Atlantic Ocean

July 5th, 2018 |

GOES-16 Band 2 (“Red Visible”, 0.64 µm) Imagery over the Atlantic Ocean, 0915-2130 UTC on 5 July 2018 (Click to animate)

The season’s second named tropical cyclone in the Atlantic Basin has formed.  GOES-16 visible imagery, above (click to play an animated gif), shows Tropical Storm Beryl moving westward just north of 10 º N Latitude between 40 º and 50 º W Longitude.  The infrared imagery (10.3 µm), the Clean Window, below shows a compact storm with cold cloud tops and a central dense overcast.

GOES-16 Band 13 (“Clean Window”, 10.3 µm) Infrared Imagery over the Atlantic Ocean, 0915-2130 UTC on 5 July 2018 (Click to animate)

Much of the tropical Atlantic north of 10 N Latitude shows little convection.  This is because of a Saharan Air Layer, shown below (in red) from a screen capture from the CIMSS Tropical Website (Click here for the latest SAL analysis). An important component of the SAL analysis is the Split Window Difference field (10.3 µm – 12.3 µm) that can diagnose both moisture and dust. The SAL analysis shows considerable dry Saharan air over the Atlantic; Beryl has formed along its southern edge. Compare the SAL analysis to the Split Window Difference field, below, that shows dry air in blue. Similar features are present in both. The GOES-16 Low-Level Water Vapor Infrared Imagery (7.34 µm), here, shows similar features as well. There are multiple ways to diagnose dry air with GOES-16.

Saharan Air Layer (SAL) Analysis, 2100 UTC on 5 July 2018 (Click to enlarge)

GOES-16 Split Window Difference field (10.3 -12.3 µm) Imagery over the Atlantic Ocean, 2100 UTC on 5 July 2018 (Click to enlarge)

NUCAPS Soundings from Suomi NPP can be used to diagnose the thermodynamics of the atmosphere surrounding Beryl. The image below shows NUCAPS Soundings locations between 1500 and 1600 UTC on 5 July 2018, and the points are color-coded to describe the data (as discussed here). A Sounding near 16.3 N, 43.1 W (north of Beryl) shows dryness at mid-levels; total precipitable water is only 1.27″. A Sounding closer to the storm, at 10.3 N, 43.5 W (west of Beryl) is much wetter: total precipitable water is 2.12″. NUCAPS Soundings are available online (over the Continental US only) here.

NUCAPS sounding locations over Beryl at 1500-1600 UTC on 5 July 2018 (Click to enlarge)

Very small (in size) Beryl is forecast to strengthen in the short term. See the National Hurricane Center website and the CIMSS Tropical Website for more information.


==== Update 6 July 2018 ====
Beryl has strengthened and is a hurricane, as of 0900 UTC on 6 July, the first hurricane of the 2018 Atlantic Hurricane season. The sandwich product animation below, courtesy Rick Kohrs and Joleen Feltz, CIMSS, that combines visible (0.64 µm) and clean window infrared (10.3 µm) imagery shows the appearance and subsequent disappearance of a very small eye.

Sandwich product that combines GOES-16 Band 2 (“Red Visible”, 0.64 µm) and Band 13 (“Clean Window”, 10.3 µm) over Beryl, 0815-1515 UTC on 6 July 2018 (Click to enlarge)