Sentinel-1A overflew the country of Savai’i and the south Pacific to its south on 1 October 2023 (Click here to view the scene at the OceanDataLab website; data are also available at NOAA/STAR’s SAR data website). A benefit of the SAR data is its remarkable horizontal resolution, manifest above as very narrow regions of strongest winds (nearly 30 knots, red in the enhancement used) within a broad region of 20-knot winds (green and yellow in the enhancement used). The southern edge of this scene is 16.8^oS, and the arcs of stronger wind start at about 14.3^oS. Metop-B and Metop-C sampled the region on 1 October, as shown below, two Advanced Scatterometer (ASCAT) views from the ascending passes (near 0900 UTC) and descending passes (near 2000 UTC).

The ca. 2000 UTC ASCAT observations shown below don’t really sample the region (between 14^o and 17^o S) sampled by SAR data above. One might be tempted to draw a line from the eastern to western swaths of strongest winds to anticipate winds of 20-25 knots to the south of Samoa, that is, an expansion northward of the observed winds at ca. 0900 UTC shown above. Peak ASCAT winds are 25 knots however, in contrast to the 30-knot SAR observations.

Consider the horizontal scale of the wind observations you are using as you interpret them.

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Persistent rains over the New York City metropolitan area have caused urban flooding on 29 September (29 September is the wettest day since 1948 in NYC well!). MIMIC TPW, above (source), shows moisture moving inland from the Atlantic Ocean. It’s often the case that heavy rain is accompanied by advection of moisture at multiple layers in the atmosphere; the Advected Layer Precipitable Water product, below (source), identifies two sources of moisture moving over metropolitan New York: moisture from the Atlantic is moving towards New York in the layer from the Surface to 850 mb; moisture from the Great Lakes is moving towards New York in the 700-500 mb layer, accompanying what appears to be a mid-level impulse. The edge of that feature from 700-500 mb is close to New York at 1800 UTC, the end of the animation, as shown in this annotated image (see the dotted orange line in the lower left image).

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GOES-16 imagery, below, shows persistent redevelopment of convection over western Long Island/metropolitan New York City. As in the ALPW fields, a boundary is approaching metropolitan New York City by the end of the animation (1851 UTC). Perhaps the passage of that boundary will lessen the likelihood of convective redevelopment (caveat: your blogger is not a paid forecaster!) Abundant moisture (values exceeding 1.6″) is to the southeast of New Jersey (reddish orange in the enhancement), with more modest values (1.3-1.4 inches, yellow in the enhancement used) over New Jersey/eastern Pennsylvania.

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GOES-16 Visible/Infrared Sandwich RGB images (above) provided a closer look at the NYC area — METAR 1-hour Precipitation Accumulations were as high as 1.96 inches at Central Park (surface observations), 1.42 inches at Farmingdale (KFRG, surface observations), 1.40 inches at La Guardia Airport (KLGA, surface observations) and 1.24 inches at Kennedy International Airport (KJFK, surface observations). Such rainfall rates contributed to the high precipitation totals across the region, which exceeded 9 inches in the NYC area.

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NOAA-20 overflew New York just before 1800 UTC on 29 September 2023. In the Sounding Availability Plot below, a line of NUCAPS profiles stretching east-northeastward from the central DelMarva peninsula are plotted in green — meaning the infrared retrieval converged to a solution — and boxed in purple. The individual profiles are shown in the animation, with locations indicated. The 3 easternmost soundings show a profile very similar to the 1200 UTC sounding at Upton, NY (also available here); that is, nearly moist adiabatic and close to saturation.

NUCAPS profiles can be horizontally interpolated to a grid. The 850-500 mb lapse rate computed from those fields is shown below. The most unstable air stretches back into northern Virginia.

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Two Mesoscale Prediction discussions from NOAA’s Weather Prediction Center (WPC) (11:35 PM on the night before the event; 5:05 AM on the morning before the event) show how well this event was anticipated.

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Scientists at CIMSS are putting a test version of the CSPP Geosphere site through its paces. The new version includes Level 2 products (Cloud Top Height, Cloud Top Pressure; both can be displayed using geo2grid software) — at full ABI resolution. The True-Color animation above shows Tropical Storms Phillipe and Rina in close proximity over the tropical Atlantic Ocean. (Rina’s exposed low-level circulation is very apparent!) The animation below include a Cloud Top Height overlay, with a scale shown. Cloud Top Heights over Rina peak at around 16000 m; those over Phillipe include values exceeding 17000 m

A toggle between the two images at 1650 UTC is shown below. Screen controls are not saved when imagery are exported, but those controls can be seen in this screenshot.

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Stay tuned for an announcement for the update to CSPP Geosphere!

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Dust RGB images (above) showed a plume of resuspended ash (brighter shades of pink) from the 1912 Novarupta-Katmai eruption in Alaska, which was being transported offshore across the Shelikof Strait toward Kodiak Island on 27 September 2023. Surface volcanic ash within the Valley Of Ten Thousand Smokes.was being lofted by strong northwesterly winds.

Volcanic ash (VA) was reported at Kodiak Airport (PADQ) for 7.5 hours, from 2123 UTC on 27 September to 0453 UTC 28 September (below) — for example, see METAR cursor sampling at 2200 UTC, 2300 UTC and 0000 UTC — but the ash was not restricting surface visibility below 10 miles.

1-minute GOES-18 Nighttime Microphysics RGB + daytime True Color RGB images from the CSPP GeoSphere site (below) provided a more detailed view of the ash plume.

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