GOES-16 (GOES-East) daytime True Color RGB and Nighttime Microphysics RGB images from the CSPP GeoSphere site (above) covered the period from 0200 UTC on 06 March to 0000 UTC on 20 March 2023 — and eventually showed the circulation of Cyclone Yaku off the coast of Peru (the clockwise circulation of Yaku was initially obscured by deep ITCZ convection, but became more evident around 11 March as the storm approached 10º S latitude). According to surface analyses from the NHC Tropical Analysis and Forecast Branch, Yaku apparently developed along the southern branch of the Eastern Pacific Double ITCZ sometime around 0000 UTC on 06 March (over an area of warm SST anomaly). As Yaku later began to move southward across colder water, deep convection diminished and its low-level circulation became more exposed from 15-19 March — and a distinct circulation was no longer seen by 0000 UTC on 20 March.

The MIMIC Total Precipitable Water product (below) revealed the clockwise circulation of Yaku on/after 04 March.

#Infórmate #Yaku, Ciclón de características tropicales no organizado, se ubica a más de 1600 Km de Lima y no ejercería influencia en la ocurrencia de lluvias sobre la costa y sierra del Perú.

?Líneas rojas, recorrido del 4 al 17 de marzo
?Líneas amarillas, probable recorrido pic.twitter.com/03aR9nI2SU

— Senamhi (@Senamhiperu) March 17, 2023

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This is the first in a series of posts on the 2023 version of PHSnMWnABI modeling. CIMSS this year will again be supplying output to the Hazardous Weather Testbed (HWT, from late May through mid-June 2023) from a modeling system that includes Polar Hyperspectral Soundings (Infrared and Microwave) that are fused with ABI data (refer to this paper or this one on Data Fusion). Blog Posts on the efficacy of this modeling system from last year’s HWT can be viewed here. Model run output is available at this website where you will see a calendar. Choose the day to view. Consider the 500-mb analysis shown below, at 1700 UTC from the 1200 UTC run on 17 March, when a slight risk of severe weather over the central Gulf Coast was forecast by the Storm Prediction Center. The strongest convection stretched southwest to northeast across extreme southeastern Louisiana into southwestern Alabama — the forecast convection has not yet reached Mobile. A second line of showers lingers over southeast Texas.

Radar observations from 1658 UTC (from this site) are shown below. There are similarities between the forecast above and reality below. Convection hasn’t reached Mobile; an area of lingering showers persists over southeast Texas. The leading edge of the storms is over greater New Orleans in southeastern Louisiana.

How did other convective-allowing models do with this event? The 4-panel below shows four different forecasts intialized, as above, at 1200 UTC and valid at 1700 UTC, 5 hours later (Imagery taken from the excellent TropicalTidbits website)

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When clear skies are present (at night!), the Nighttime Microphysics RGB provides little information about the overlying atmosphere. You might see nice Sea Surface Temperature gradients, as in the image below from the CSPP Geosphere site; the North Wall of the Gulf Stream is readily apparent to the east of North Carolina and Virginia.

Can you identify gradients in moisture, or in stability, in the still image above? How about in the animation below from the CONUS (PACUS) sector of GOES-18? This is a big challenge, as knowledge of moisture and stability is important for situational awareness. GOES-R Level 2 products can be added to the animation to better define the thermodynamics of the atmosphere.

Add (clear sky only) Total Precipitable Water (or K Index), two level 2 derived products, underneath the RGB above, as in the animations below. Despite cloudiness, the longitudinally-constrained ribbon of relatively moist air (about 1.5″ in its center versus 1.2-1.3 to the north and south) approaching the central Mexican coast is apparent. Instability, however, shows a wider distribution. In both cases, the satellite is giving more information than can be inferred from just the RGB. It does take practice, however, to separate the colors of the RGB from the colors of the color enhancements used in the TPW or K Index fields.

The Level 2 Moisture distribution, above, is consistent with microwave estimates of moisture from the MIMIC Total Precipitable Water site, below.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) included an overlay of GLM Flash Extent Density and surface fronts — which showed severe thunderstorms that developed across southern Oklahoma (along and ahead of a cold front) and North Texas (ahead of a dryline) during the afternoon and evening hours on 16 March 2023.

1-minute GOES-16 Visible images (above) included time-matched (+/- 3 minutes) plots of SPC Storm Reports — which included a few tornadoes in Texas, hail as large as 2.40 inches in diameter in Oklahoma and 3.00 inches in Texas, and wind gusts as high as 65 knots in Oklahoma.

The corresponding 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images with plots of time-matched SPC Storm Reports (below) indicated that some of the thunderstorm overshooting tops exhibited infrared brightness temperatures in the -70 to -73ºC range (lighter gray pixels embedded within darker black regions).

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