Hyperspectral modeling during severe weather

March 23rd, 2022 |

Hyperspectral soundings — for example the Cross-track Infrared Sounder (CrIS) on NOAA-20/Suomi-NPP and the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp — observe the atmosphere at thousands of wavelengths in the near-infrared and infrared part of the electromagnetic spectrum. The excellent spectral resolution allows for good vertical resolution of temperature and (especially) moisture in the atmosphere; Polar Hyperspectral Soundings (PHS) are created from these data to give profiles of temperature and moisture. Data fusion, described in this Smith et al. paper from 2020, relates ABI information to PHS when the polar observations are made (the technique used is a bit different from the GEO+LEO technique described in this Weisz and Menzel paper from 2019). Those relationships are subsequently carried forward in time, thereby exploiting both the excellent spectral resolution available from polar satellites and the excellent spatial and temporal resolution from ABI. Qi Zhang and Bill Smith, Sr. at Hampton University are running a model that takes advantage of this data fusion. Output from this modeling effort have been previously discussed here and here on this blog, and is available here. In the past year, the modeling effort has expanded to include microwave information (from the Advanced Technology Microwave Sounder (ATMS) on NOAA-20/Suomi-NPP) to give more accurate satellite-derived moisture information below the cloud-tops.

The imagery below shows forecasts of Significant Tornado Parameter from two different 3-km runs, one with a domain centered on the risk as defined by the Storm Prediction Center, one with a static domain. Note the close correlation between the region of larger values and the observed tornadoes. Results between the two forecasts are similar, but the false alarm rate is somewhat smaller in the small domain.

SPC Storm Reports from 21 March 2022 (left), and model fields of Significant Tornado Potential, hourly from 0300 to 0600 UTC on 22 March (right) (Click to enlarge)

New Orleans LA was hit by a tornado (discussed here) after sunset on 22 March 2022. Tornado locations are shown by the inverted red triangles in the figures below. The Significant Tornado Parameters from the 3-km model that includes PHS data, microwave data, and ABI data has a maximum in the region of the tornado. This is useful information to have when anticipating the tornado development.

The combination of polar hyperspectral soundings with ABI data has been explored since before the launch of GOES-R, and in fact back to about 2008! Funding for this effort has been supplied in the past by both GOES-R and JPSS Risk Reduction initiatives.

In the (distant) future, when NOAA’s Geostationary Extended Observations (GeoXO) satellite system is in orbit (click here for more information on GeoXO), routine soundings of the atmosphere will allow this type of modeling effort with better initial conditions because there will be a much smaller time between the observations (from Geostationary in the future vs. from Polar Orbiters now) and the model initialization.

Cyclone Batsirai reaches Category 4 intensity

February 3rd, 2022 |

EWS-G1 Infrared Window (10.7 µm) images [click to play animated GIF | MP4]

US Space Force EWS-G1 (formerly GOES-13) Infrared Window (10.7 µm) images (above) showed Cyclone Batsirai in the South Indian Ocean — just north of the island nations of Mauritius and Réunion — during the time period it was classified as a Category 4 intensity storm (00 UTC on 02 February to 15 UTC on 03 February 2022). Note that the small-diameter eye became notably larger by the end of the animation.

A DMSP-17 SSMIS Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) displayed evidence that Batsirai had recently completed an eyewall replacement cycle (ERC), with the faint signature of the original small-diameter eye surrounded by the new large-diameter eye. This ERC process — seen in a 48-hour MIMIC-TC animation — initiated Batsirai’s gradual  decline in intensity.

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

EWS-G1 Visible (0.63 µm) images (below) showed that the small eye was initially cloud-filled, but eventually cleared during the day on 02 February — to reveal the possible existence of eye mesovortices (although such features are difficult to diagnose using 30-minute images) .

EWS-G1 Visible (0.63 µm) images [click to play animated GIF | MP4]

Cyclone Batsirai in the southern Indian Ocean

February 1st, 2022 |
MIMIC Total Precipitable Water estimates, 2100 UTC 31 January – 2000 UTC 1 February 2022 (click to enlarge)

MIMIC Total Precipitable Water esimates over the Indian Ocean for the 24 hours ending at 2000 UTC on 1 February 2022, above, show the strong cyclonic circulation associated with Cyclone Basirai. Its forecast motion is westward towards Madagascar, as shown in the toggle below that also includes sea-surface temperatures and Window Channel (showing a well-structured storm; all images are from the SSEC/CIMSS Tropical Website). A wind shear analysis (also from the SSEC Tropical Website and valid at 1800 UTC on 1 February) for the Indian Ocean shows low shear values over the storm, but relatively high shear between the storm and the island of Madagascar.

Forecast Path for Batsirai, sea-surface temperature analysis, and window channel satellite imagery, times as indicated (Click to enlarge)

Batsirai’s path moves it close to Mozambique/Malawi, two countries that are still being flooded as a result of rains from Tropical Storm Ana a week ago. A VIIRS flood analysis (from this website), below, diagnoses active flooding occurring along the Shire River (south of Lake Malawi) and along the Zambezi River on 31 January 2022.

River Flood Analysis from VIIRS imagery, 5-day composite endings 31 January 2022 (click to enlarge)

For more information on Batsirai, consult the RSMC at La Réunion (click ici) or the SSEC Tropical Website.

Heavy Rain threat over the Samoan Islands

January 27th, 2022 |
MIMIC Total Precipitable Water over the South Pacific Ocean, 0000 UTC on 25 January – 2100 UTC on 27 January 2022 (click to enlarge)

Microwave-derived estimates of Total Precipitable Water (TPW), above, from MIMIC TPW, show an increase in moisture around the Samoan Islands to the west of 170o W. Percent of Normal mappings of blended TPW in this region, as shown below (taken from this site), show values at >150% of normal.

Percent-of-Normal TPW from the NOAA/NESDIS Blended TPW Product website, 1800 UTC on 27 January 2022 (Click to enlarge)

In anticipation of heavy rains, the National Weather Service Pacific Region requested a Mesoscale Domain (a complete list of messages is here) centered on Tutuila, the main island of American Samoa, through 1100 UTC on 28 January. An animation of GOES-17 Band 13, below, (every 5 minutes, rather than the 1-minute cadence of Mesoscale domains) overlain on top of the Level 2 Total Precipitable Water product (a product that is computed hourly for the Full Disk domain), shows a focus of convection moving westward over American Samoa and Samoa. Note the degradation of the Level 2 Product TPW that is associated with the poor functionality of the Loop Heat Pipe on GOES-17 that occurs at night. Magenta values in the TPW enhancement signify values exceeding 2″. Samoa and American Samoa are within a ribbon of exceptional moisture.

GOES-17 Mesoscale 2 domain Band 13 (Clean Window, 10.35 µm) overlain on top of clear-sky Full Disk Total Precipitable Water, 0900 – 2144 UTC on 28 January 2022 (Click to enlarge)

GOES-17 Visible Imagery, below, during the daytime, also show widespread convection moving into the Samoan waters. A benefit of the visible imagery is that surface lines of convergence that may initiate convection are apparent with the 5-minute cadence shown below; those lines are even more apparent in 1-minute imagery (shown here from 1825 – 2234 UTC)

GOES-17 Band 2 Visible (0.64 µm) Imagery, 1734 – 2144 UTC on 27 January 2022 (Click to enlarge)

Added, 28 January: the two final hours of the mesoscale domain are shown below. The axis of the deepest moisture has shifted westward through the mesoscale domain from the previous day; showers continue to develop.

GOES-17 Clean Window infrared (Band 13, 10.35 µm) and Total Precipitable Water, 0903 – 1102 UTC (Click to enlarge)