GOES-17 (GOES-West) “Clean” Infrared Window (10.35 µm) images (above) showed the movement of numerous thunderstorms across American Samoa during the 16-18 February 2020 period. This deep convection was being forced by an active South Pacific Convergence Zone or “Monsoon Trough” (surface analysis) and the presence of Tropical Invest 96P (named TD07F by the Fiji Met Service / Nadi Tropical Cyclone Centre) northwest of Samoa. Due to outflow from a nearby thunderstorm, winds gusted to 60 knots at Pago Pago, American Samoa (NSTU) at 11 UTC on 17 February.

With an increasing probability of Invest 96P becoming better organized (aided by low values of deep-layer wind shear along with modest upper-level divergence), a GOES-17 Mesoscale Domain Sector was positioned over the Samoan Islands on 18 February — providing “Red” Visible (0.64 µm) and “Clean” Infrared Window images at 1-minute intervals (below). During this period, the coldest convective overshooting tops exhibited infrared brightness temperatures in the -80 to -85ºC range (which corresponded to the tropopause temperatures seen in Pago Pago rawinsonde data).

===== 20 February Update =====

Another tropical depression (Invest 97P/TD09F) developed along the active Monsoon Trough on 20 February (surface analyses), intensifying just south of American Samoa to become Tropical Cyclone Vicky (TC 17P) as of 18 UTC (JTWC advisory). Once again a GOES-17 Mesoscale Sector was positioned over the region — “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the gradual organization of Vicky; the coldest cloud-top infrared brightness temperature of convective overshooting tops was -90ºC. Surface observations revealed a wind gust to 65 knots at Pago Pago, American Samoa just before 20 UTC.

GOES-17 Infrared Window (11.2 µm) images from the CIMSS Tropical Cyclones site (below) showed that Vicky was moving through an environment characterized by of low values of Deep Layer Wind Shear, a favorable factor for further intensification.

Hourly MIMIC Total Precipitable Water images during the 16-20 February period (below) displayed the northwest-to-southeast oriented band of elevated moisture along the South Pacific Convergence Zone (or Monsoon Trough). The Samoan Islands are centered near 14.3° S latitude, 170.1° W longitude.

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GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the circulations associated with a pair of Hurricane Force low (surface analyses) during the 13-15 February 2020 period. At the limb of the GOES-16 Full Disk view, plots of hourly surface wind revealed gusts in the 70-80 knots range at stations in Iceland — including Keflavik International Airport near Reykjavik and Akurnes along the southeast coast. One site north of Reykjavik recorded a wind gust of 138 knots.

Sequences of VIIRS Infrared Window (11.45 µm) and True Color RGB images from NOAA-20 and Suomi NPP during those same days as viewed using RealEarth are shown below.

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images during the 14-16 February period are shown below. Named “Storm Dennis” by the UK Met Office, the system brought high winds to much of Europe.

Additional information about this event is available on the Satellite Liaison Blog.

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Prediction: This is the most beautiful satellite image you will see today. The above imagery, from the talented Rick Kohrs at the Space Science and Engineering Center, knits (seemingly seamlessly) together vertical local-noon swaths of multispectral visible/near-infrared Geostationary imagery, all using McIDAS-X. At some point in the near future, daily imagery will be created, and then an annual movie. (Click here for an image from 21 March 2019, or from 21 September 2019).

In each image, the sub-point of a satellite used to create the image is evident in the Sun Glint (at 140.2ºE for Himawari-8, or 137.2ºW and 75.2ºW for GOES-17 and GOES-16, respectively). Values at the eastern and western edges do not match up because they are offset by 1 day. A break-point has to be inserted, so why not at the edge?

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GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed a large Mesoscale Convective System (MCS) west of Resistencia (station identifier SARE) in far northern Argentina on 14 February 2020 — this MCS developed southeast of an area of low pressure that was situated well north of a slow-moving cold front (surface analyses). The coldest GOES-16 cloud-top infrared brightness temperature was -94.1ºC on the 0750 UTC image.

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 0452 UTC) and Suomi NPP (at 0541 UTC) as viewed using RealEarth (below) revealed intricate patterns of cloud-top waves and radial banding.

Plots of available NOAA-20 NUCAPS sounding points are shown below. NUCAPS profiles immediately north and south of the MCS revealed a very moist and unstable atmosphere, with Total Precipitable Water values around 2.4 inches and Most Unstable air parcel Convective Available Potential Energy (CAPE) values of 4500-5200 J/kg. The red NUCAPS profile dots indicate points where both the infrared and microwave retrievals failed — these are located within the core of the MCS.

Plots of rawinsonde data from Córdoba, Argentina (below) — located not far southwest of the MCS — indicated a tropopause temperature of -74.7ºC at an altitude of 16.4 km on 14 February at 12 UTC.

 

You’ll have to add one @70_dbz… Here is a MCS over Argentina early this morn (0748 UTC). 18 km deep (according to GPM-DPR), with a -92 degC brightness temperature (according to GOES-16, on NASA Worldview). What. A. Beast. https://t.co/KkSVpETkuk pic.twitter.com/KJU3jieuCp

— Randy Chase (@DopplerChase) February 14, 2020

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