1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) + Total Precipitable Water (TPW) images (above) showed severe thunderstorms that developed along a cold front that moved north-northeast across Argentina and Uruguay on 01-02 December 2023. Pulses of thunderstorm overshooting tops occasionally exhibited infrared brightness temperatures in the -85 to -90ºC range (brighter white pixels embedded within black-enhanced cloud regions). North of the advancing front, TPW values were in the 2.0 to 2.3 inch range (lighter shades of violet), while TPW values decreased to the 0.5 to 0.7 inch range (lighter shades of blue) behind the front.

At Montevideo (METAR site SUAA, located along the southern coast of Uruguay), thunderstorms produced a peak wind gust of 54 knots (62 mph) at 1615 UTC on 01 December (below) — along with rainfall of 80 mm (3.15 in) in a 6-hour period, resulting in significant flooding.

Farther to the west over northern Argentina, strong winds from a convective outflow boundary (just ahead of the cold front) produced blowing dust that reduced the surface visibility at Rosario (SAAR), Santa Fe (SAAV) and Parana (SAAP) (below).

Low clouds within the north-northeast moving convective outflow boundary were apparent in GOES-16 True Color RGB images from the  CSPP GeoSphere site (below).

View only this post Read Less

In July 2022, significant flooding affected metropolitan St. Louis as multiple convective cells trained through the area. (This blog post contains clean window imagery for 26 July portion of the two-day event; the St Louis WFO also discussed the event). This WPC discussion describes the atmospheric setup on 25 July.

A retrospective model run for this flooding event was created using a WRF simulation. The model had 2-km resolution and data were output every 15 minutes. The WRF data were input into a CRTM to convolve the spectral response function at 5.15 micrometers — the novel water vapor channel that is planned for the GeoXO Imager (the follow-on to GOES-R’s ABI) that is planned for launch in the mid-2030s. Weighting functions that compare the 5.15 µm channel with GOES-R channels at 6.19 µm, 6.95 µm and 7.3 µm (for approximately the same atmosphere), below, show much more information from the boundary layer (850 mb and below) sensed by a satellite that detects energy at 5.15 µm compared to longer wavelengths. The image below was created from this image for 5.15 and this image for GOES-R Bands 8-10.

What does the model output tell you? Consider the toggle below. The 5.15 µm imagery shows a region of cooler temperatures (yellow in the enhancement used vs. orange to the north and south) over Nebraska and Kansas into Missouri as highlighted by the blue arrows; a similar distribution is apparent in the 7.3 µm imagery — blue in the enhancement from Kansas/Nebraska into Missouri vs. yellow to the north and south. The cooler brightness temperatures mean that the height of the moisture layer detected is higher in the atmosphere; a likely reason for this moisture distribution is that more moisture is present in this corridor just to the north of a stationary front.

How do the fields change as convection starts to initiate? That is shown in the animation below that covers the times 0000 UTC to 0515 UTC on 25 July 2022. In particular, the 5.15 µm imagery, with a signal that includes more information from lower in the boundary layer, can detect the low-level development of convection over Kansas and Missouri at earlier times than occurs in the 7.3 µm imagery. Compare the cooler brightness temperatures especially between 0230 UTC and 0400 UTC over Kansas and Missouri. The 0345 UTC image, shown below the animation, shows significant 5.15 µm cooling in/around Kansas City (northeast Kansas/western Missouri) that is not as apparent in the 7.3 µm imagery. The lowest-level ‘water vapor’ imagery at 5.15 µm is giving a heads up for convective development about 90 minutes before it appears in the 7.3 µm imagery.

The mp4 animation below shows four water vapor channels from the model simulation every 15 minutes from 0000 UTC – 2345 UTC on 25 July. In addition to the earlier detection of developing convection over central Kansas/Missouri mentioned above, note how the convection initially over southern Missouri dissipates as it moves into regions with warmer brightness temperatures (where low-level moisture is perhaps not quite so abundant). Surface features are visible over Wyoming in the 5.15 µm, especially as the surface warms during the day, indicating information from the surface could be sensed in addition to information related to the distribution of water vapor. Keep in mind these types of very dry regions are not likely candidates for convective initiation. Regions with moderate to high amounts of low-level moisture are less suspectible to this type of surface contamination, making the 5.15um band very useful for early detection of severe storms.

---

Thanks to Zhenglong Li, Nate Miller and Mat Gunshor, CIMSS for these images! For more information on GeoXO, click here.

View only this post Read Less

Hourly GOES-West imagery from the CSPP Geosphere site, above (direct link to animation), shows the development of a broad Kona Low over the Hawai’ian islands. MIMIC Total Precipitable Water (TPW) fields over the eastern Pacific, below, show a very moist airmass moving into the eastern Hawai’ian islands as the Kona low develops to the west. The OSPO Percent of Normal fields at 1200 UTC on the 29th (here), show values >150% of normal throughout the Hawai’ian island chain. The next few days will be wet in Hawai’i — the entire state is under either Flood Watches or Flood Advisories.

Airmass RGB imagery, below, from GOES-18 shows the dark green coloration that is characteristic of deep tropical moisture to the south of Hawai’i. The developing Kona Low, to the west of Kauai, is surrounded by air rich in potential vorticity, as suggested by the orange tint in the RGB. The developing low is also cut off from the main belt of westerlies that are north of 40^oN Latitude.

---

NOAA-20 overflew the Hawai’ian island chain around 0000 and 1200 UTC on 29 November. The near-full Moon on the 29th provided ample illumination for the Day Night Band imagery, shown below. A developing low is obvious to the west of Kauai, and convective clouds associated with rich moisture shown in the MIMIC animation above is apparent over the Hawai’i.

NUCAPS data from two sequential NOAA-20 overpasses can be used to assess how the atmosphere is changing. The toggle below compares NUCAPS’ estimate of 500-mb temperature at 2339 UTC on the 28th and 1210 UTC on the 29th. The -12^oC isotherm moves south during these 12 hours although the -16^oC isotherm retreats northward.

The toggle below compares NUCAPS profiles near 20 N, 166 W. Significant upper-tropospheric cooling is apparent between 2345 UTC on 28 November and 1214 UTC on 29 November!

The 0000 and 1200 UTC soundings at Lihue, below, also show cooling in mid-levels during the 12 hours.

The Direct Broadcast antenna in Honolulu (link) is a useful source for microwave estimates for rainrate derived from polar orbiting satellite for systems affecting Hawai’i. The toggle below shows rainrate from MetopC (0744 UTC) and NOAA-20 (1208 UTC); heavy rain has moved onto the Big Island from the southeast, and it is slowly approaching Kauai from the west

For more information on this wet event, refer to the National Weather Service office in Honolulu.

View only this post Read Less

10-minute interval GOES-16 (GOES-East) True Color RGB images (source) from 0930-1900 UTC on 13-26 November 2023 (above) showed Iceberg A23a just east-northeast of Joinville Island (at the tip of the Antarctic Peninsula). Although cloud-free periods were scarce during those 14 days, even on most of the cloudy days the silhouette of A23a was evident. During that time, A23a was the largest iceberg in the world (although it was smaller in area than recent icebergs such as A68).

On 2 days in mid-November when cloud cover was at a minimum, a toggle between “Natural Color” RGB images from Landsat-9 (at 1239 UTC on 14 November) and Landsat-8 (at 1233 UTC on 15 November) is shown below (source) — which revealed a small amount of westward drift during that 24-hour period.

While the NOAA-20 VIIRS Sea Ice Temperature derived product at 0000 UTC on 13 November (below) generally displayed values near or just below freezing (medium shades of orange) across much of the surface of A23a, there were some areas across the northern portion of the iceberg that exhibited above-freezing values (darker shades of orange) as warm as 274.4 K or +1.25C (suggesting that some surface melting was occurring).

However, on 27 November GOES-16 True Color RGB images (below) showed that fractures — likely induced by wind stress as an occluded cyclone moved across the area (surface analyses) — began developing within the southern and eastern portions of A23a.

View only this post Read Less