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)

SAR data for winds and ice over the Great Lakes

January 10th, 2022 |
Radarsat Constellation Mission (RCM) observations over Lake Superior, 11:59 UTC on 10 January 2022 (Click to enlarge)

Data from this site shows SAR observations over the Great Lakes daily around 0000 and 1200 UTC. The image above shows SAR data over Lake Superior just before 1200 UTC on 10 January. The background flow used in processing shows strong northwesterly winds. Note the relative calm in the lee of the Keewenah peninsula, and an interesting boundary in the winds near Michipicoten Island. As noted in this blog post from December, the strongest winds are likely associated with enhanced Lake-Effect bands, as enhanced vertical mixing in those bands will allow stronger upper level winds to mix down to the lake surface.

Does ABI imagery show enhancements in the regions where the SAR data indicates enhanced mixing with convective bands? Consider the 3.9 µm image below (from this NOAA/STAR website) from 1201 UTC. Cold cloud tops northeast of Marquette MI do correlate well with the strong winds in that regions.

GOES-16 Band 7 (3.9 µm) at 1201 UTC on 10 January 2022 (click to enlarge)

Scatterometry can also be used to measure winds on the lake surface. The imagery below (from this website) shows vectors from the Chinese HY-2B scatterometer at 1330 UTC. Spatial resolution for this imagery is much coarser, and observations closer to shore do not occur. Northwest winds of at least 30 knots are indicated however.

HY-2B scatterometry at 1310 UTC, 10 January 2022 (Click to enlarge)

A careful observer of the SAR winds above might notice very strong winds in/around Little Bay de Noc, the northeastern part of Green Bay. Care must be taken to differentiate between ice and winds in regions where ice is present, as SAR data can be also used to identify regions of ice. The toggle below of NOAA-20 True and False color imagery over the western Great Lakes (from the VIIRS today website) does show cyan regions — typical of ice — over northeastern Green Bay. (Click here for highest resolution False Color imagery from NOAA-20 on 9 January)

NOAA-20 True and False color over the Great Lakes, 9 January 2022 (Click to enlarge)

What kind of wave heights are these strong northwesterly winds generating over Lake Superior? Altimetric data from SMAP, below, (source) shows 6-8 foot waves over western Lake Superior. The longer fetch for the region northeast of Marquette probably means much higher waves there.

Wave Heights (feet) at ~0315 UTC on 10 January 2022 (click to enlarge)

Tropical disturbance near Fiji

January 7th, 2022 |
GOES-17 Geocolor imagery and Flash Extent Density, 1506-1911 UTC on 7 January 2022 (Click to enlarge)

GOES-17 ABI and GLM imagery (from this NOAA STAR website), above, over the southern Pacific Ocean show a region of potential tropical cyclogenesis to the west of Fiji, near the western boundary of this mapping. This Invest Area has been percolating for much of the week. Despite low values of shear (shown below, from this website) and warm sea-surface temperatures, intensification to a tropical depression has not yet occurred (see this discussion from the Joint Typhoon Warning Center). However, GLM observations of Flash Extent Density (FED) do show occasional lightning events within the developing system.

Diagnosed wind shear, 1800 UTC on 07 January 2022 (Click to enlarge)

Upper-level water vapor imagery (GOES-17 Band 8, at 6.19 µm), below, from 1940 UTC, shows a distinct cirrus overcast at about 17 S, 172 E. Substantial dry air is not indicated in the water vapor imagery, nor in a MIMIC TPW mapping from 1200 UTC (downloaded from here), shown below.

Upper-level water vapor imagery (GOES-17 Band 8, 6.19 µm), 1930 UTC on 7 January 2022 (Click to enlarge)
MIMIC Total Precipitable Water fields, 1200 UTC on 7 January 2022 (Click to enlarge)

Scatterometry over this system on 7 January (downloaded from this website), show an increase in symmetry to the storm between the HY-2B overpass at 0630 UTC and the HY-2C overpass at 1330 UTC. For more information on this system over the weekend, refer to the SSEC/CIMSS Tropical Website, the Joint Typhoon Warning Center, and the Fiji Meteorological Service.

Scatterometery over the south Pacific, 0630 and 1330 UTC on 7 January 2022 (Click to enlarge)

Ozone and the airmass RGB

December 13th, 2021 |
GOES_17 airmass RGB, 2200 UTC on 12 December 2021 (Click to enlarge)

A GOES-17 airmass RGB, above, shows a strong feature in the Gulf of Alaska. It’s common to associate the orange and purple regions within that polar feature (that is accompanied by cloud features consistent with very cold air aloft) with enhanced ozone. What products are available online to gauge the amount of ozone?

The OMPS instrument on board NOAA-20 (and on Suomi-NPP) senses in the ultraviolet (from 250-310 nm) to compute ozone concentration. (For more information on OMPS, refer to this document) The figure below, taken from this Finnish website, shows ozone concentration for the 24 hours ending at 0110 UTC on 13 December. A distinct maximum is apparent over the Gulf of Alaska. Note the northern terminus of the observations that are related to the time of year: there is little Sun north of 60 N. The data for this were downloaded from the Direct Broadcast site at GINA at the University of Alaska-Fairbanks. OMPS data are also available (from Suomi-NPP) at NASA Worldview.

To determine the time of the data in the image below, consult the NOAA-20 orbital paths here. This image (from that site) shows a NOAA-20 ascending overpass between 2235 and 2245 UTC over the Gulf of Alaska.

Daily Composite of Ozone concentration for the 24 hours ending 0111 UTC on 13 December 2021 (click to enlarge)

NOAA-20 also carries the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) instruments that are used to create NUCAPS vertical profiles; one of the trace gases retrieved in this way is ozone. The distribution of ozone (with values in regions where it was dark) from NUCAPS is shown below (from this website maintained by SPoRT), and it corresponds roughly with the OMPS estimates shown above.

Gridded NUCAPS estimates of ozone, 2217 UTC on 12 December 2021 (Click to enlarge)

Conclusion: The assumption that upper-tropospheric ozone values are large in regions where the airmass RGB is tinted red or purple is a good assumption, especially if other structures in the RGB — such as cumulus cloud development in the cold air — reinforce the idea that an intrusion of stratospheric air is occurring. The strong storm that this lowered tropopause is supporting is accompanied by a moist feed of air moving into central California, as shown below by MIMIC total precipitable water fields.

Total Precipitable Water, 2200 UTC on 12 December 2021 (Click to enlarge)

Gridded NUCAPS fields are being tested within RealEarth, as shown below. They should be generally available soon.

RealEarth Gridded NUCAPS estimates of ozone, 2217 UTC on 12 December 2021 (Click to enlarge)