Hurricane Nicholas makes landfall in Texas

September 14th, 2021 |
GOES-16 Mesoscale Sector infrared imagery (Band 13, 10.3), 0321-0844 UTC on 14 September 2021

Hurricane Nicholas made landfall on the Gulf Coast shortly after 0530 UTC on 14 September. It is a challenge to determine the storm center from the animation above, although deep convection is suggestive of its location. Note the collapse of deep convection as well at the end of the animation. Radar imagery, below (from this site), is helpful in placing the storm center.

NEXRAD Composite Reflectivity, 0524, 0534, 0544, 0554 UTC on 14 September 2021 (Click to enlarge)

MetOp-B overflew Nicholas at 0315 UTC shortly before landfall. ASCAT winds (from this site) at 0315 UTC show the circulation center very close to the shoreline. A similar image from the OSI SAF Multiplatform viewer is here.

Metop-B ASCAT winds, 0314 UTC on 14 September 2021 (Click to enlarge)

Nicholas is embedded in very moist air. A 24-hour MIMIC Total Precipitable Water animation, below, shows the moisture plume. Heavy rain is forecast for the central Gulf Coast.

Total Precipitable Water, 1000 UTC on 13 September – 0900 UTC 14 September (click to enlarge)

Nicholas has weakened to a Tropical Storm as of 0900 UTC on 14 September. Refer to the National Hurricane Center website for more information.

Hurricane Ida develops an eye over the Gulf of Mexico, as intensification continues until landfall

August 28th, 2021 |

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-–minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above)  showed that Hurricane Ida gradually developed an eye, as the Category 1 storm intensified to Category 2 by 1800 UTC on 28 August 2021.

DMSP-17 SSMIS Microwave (85 GHz) image at 1235 UTC [click to enlarge]

Microwave (85 GHz) images from DMSP-17 (above) and DMSP-16 (below) — from the CIMSS Tropical Cyclones site — provided 2 views of the eye and eyewall structure at 1235 UTC and 2205 UTC, respectively.

DMSP-16 SSMIS Microwave (85 GHz) image at 2205 UTC [click to enlarge]

Ida was moving across very warm water (SST | OHC) — and was forecast to pass over an area of very high Ocean Heat Content associated with a warm eddy that was shed from the Gulf of Mexico’s Loop Current. Ida was also moving through an environment of low wind shear (below), which favored further intensification as it continued to approach the Louisiana coast.

GOES-16 Infrared images, with contours of deep-layer wind shear at 20 UTC [click to enlarge]

===== 29 August Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

Ida reached Category 4 intensity at 0600 UTC on 29 August; 1-minute GOES-16 Infrared and Visible images (above) depicted a well-defined eye during the hours leading up to the hurricane making landfall along the coast of Louisiana at 1655 UTC.

GMI Microwave imagery at 1510 UTC (below) portrayed a closed eye, with the heaviest precipitation located within the eastern semicircle of Ida.

GMI Microwave (85 GHz) image at 1510 UTC [click to enlarge]

A closer view of 1-minute GOES-16 Visible images (below) revealed the presence of low-level mesovortices within the eye of Ida — a feature often observed with high-intensity tropical cyclones. The mesovortices persisted as the hurricane moved inland, as Ida was slow to weaken. Just east of the eye, Galliano (KGAO) reported wind gusts as high as 85 knots (plot | text), before observations ceased after 21 UTC (presumably due to power outages).  A separate mesonet station at Galliano recorded a wind gust of 122 mph (NWS New Orleans tweet | plot).

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

The MIMIC Total Precipitable Water product (below) showed that Ida was transporting rich tropical moisture northward across the central Gulf of Mexico coast of the US, raising a threat for flooding rainfall. 

MIMIC Total Precipitable Water product, 28-29 August [click to enlarge]

Tropical Depression Nine (now: Tropical Storm Ida) in the western Caribbean

August 26th, 2021 |
VIIRS I01 (0.64 µm) imagery with ACSPO SSTs plotted in clear regions, 1838 UTC on 26 August 2021 (Click to enlarge)

The National Hurricane Center is issuing advisories on a strong Tropical Depression in the western Caribbean Sea, centered to the west of Jamaica — in the southeast corner of the image above. This system is at the edge of the observing capabilities from the CIMSS Direct Broadcast antenna, but the image above, created from that data stream, does show the very warm Gulf of Mexico waters over which the system is forecast to move (much of the orange/red enhancement shows temperatures at/above 30 C/86 F!)

AMSR-2 Microwave imagery from JAXA‘s GCOM-W1 satellite, below, shows an unorganized storm, but plenty of ongoing convection. At the time of this imagery (1802 UTC), the storm was centered near 17.5 N, 69.5 W.

AMSR-2 imagery at 36.5 and 89.0 GHz, 1814 UTC on 26 August 2021 (Click to enlarge)

More information on this system is available at the National Hurricane Center. When named, this storm will be Ida.

Ida was named shortly after 2100 UTC on 26 August. Day Night Band imagery at 0658 UTC on 27 August 2021, below, shows Ida south of Cuba, with indication of shear: the strong convection is displaced slightly to the northeast of the surface circulation (inferred by the curvature in the low-level cumulus). Ida at this time displayed no lightning activity (unlike the convection in the central Gulf of Mexico).

VIIRS Day-Night Band visible (0.70 µm) imagery, 0658 UTC 27 August 2021 (click to enlarge)

SAR Winds over the Pacific Ocean

August 25th, 2021 |
RCM2 SAR Winds over the Pacific Ocean near 51 N, 138 W at 1528 UTC on 25 August 2021 (Click to enlarge)

Synthetic Aperture Radar (SAR) winds over the northwest Pacific, above, derived from Radar Constellation Mission (RCM) Satellite #2, shows a narrow ribbon of strong winds (>30 knots) stretching from 50 N, 138 W towards 53 N, 140 W. What kind of cloud imagery is associated with this wind feature?

Near-sunrise visible imagery from GOES-17, below, shows a narrow band of low-level clouds aligned with the region of stronger winds. This does not appear to be a deep feature: cloud shadows are much larger along the eastern edge of the visible image, which region is east of the SAR domain shown above.

GOES-17 Band 2 (0.64 µm) Visible Imagery at 1520 UTC on 25 August 2021, with and without Lat/Lon lines (Click to enlarge)

A zoomed-out 10.3 µm infrared image, below, documents how subtle the cloud feature associated with the strong winds is. Blue arrows point to the region of strong winds.

GOES-17 Band 13 Clean Window infrared (10.3 µm) imagery, 1520 UTC on 25 August 2021 (Click to enlarge)

SAR Winds are available from a variety of different satellites at this link.