Rotation off the coast of California near San Francisco was present on Tuesday 2023-03-21 as the area got hit with rains and high windspeeds. The rotation is apparent in both visible RGB satellite imagery and radar reflectivity, animated below using RealEarth. Circular formations in cloud structure, seen by GOES-16, and rain bands picked up in the radar, are visible.

Flood advisories have been issued along much of the state of California, including Los Angeles and Orange Counties. Windspeeds as high as 102 mph were reported near Santa Clarita, CA and 74 mph in Oakland, CA.

California isn’t the only state in the region to experience an excess in rain. Much of central and Northern Arizona are also under flood warnings. Below, the ‘Excessive Rainfall Outlook’ product is displayed in RealEarth. The Excessive Rainfall Outlook is a forecast of the likelihood that rainfall will exceed flash flood guidance (FFG) at a point. This product is issued by the Weather Prediction Center (WPC).

More than 121,000 Californians were without power Wednesday morning and two have been killed by fallen trees.

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By animating daily NOAA GOES-16 ABI Full Disk true color imagery, how the Earth is illuminated over time can be seen. For example, how the terminator falls on the Earth until the Equinox. For details, see “What is a Solstice?” by SciJinks. Or this NOAA post.

11 UTC loops from the (northern hemisphere) fall Equinox to the Spring Equinox. These posted GOES ABI Full Disk imagery are only showing a small number of the pixels, for a fuller resolution image at one time (20-March-2023).

The above loop, and a smaller size. The 16 bands of ABI from GOES-West and GOES-East from UW/CIMSS.

Interactive web page

An interactive web page with half a years worth of GOES ABI Full Disk visible images at 11 UTC. The beginning date is the (northern hemisphere) fall equinox in 2022 and the end date is the spring equinox in 2023. A user can play the animation, as well as annotate the images. For example, draw lines along the terminator for different times of the year. One example might be to compare a solstice to an equinox. Can you estimate the day of the summery equinox? H/T Tom Whittaker, SSEC, for the webapp, as well as those below.

Webapps about the Seasons

H/T

These images were made using NOAA data with geo2grid software, from UW-Madison, SSEC. T. Whittaker is thanked for the webapps.

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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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