Severe thunderstorms in the Northeast US

July 1st, 2017 |

* GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing *

As noted in the Tweet above from NWS Gray/Portland ME, a record number of tornado warnings were issued by that office on 01 July 2017. According to their damage surveys, the tornadoes were rated EF-0 to EF-1, with some straight-line wind damage also seen. GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports (below; also available as a 98-Mbyte animated GIF) displayed the overshooting tops and colder cloud-top infrared brightness temperatures associated with some of the thunderstorms. Note the significant offset between cloud-top features and storm reports — this is due to parallax from the large viewing angle of the GOES-16 satellite (which is positioned over the Equator at 105º West longitude).

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports in red on Visible, and in black on Infrared [click to play MP4 animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports in red on Visible, and in black on Infrared [click to play MP4 animation]

A comparison of Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1744 UTC (below) showed the early stages of convective development in far southwestern Maine, in addition to well-developed thunderstorms in eastern New York (which would later move northeastward to produce a swath of heavy rainfall that caused flooding at some locations).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11..45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11..45 µm) images [click to enlarge]

Thunderstorm development was fueled by high amounts of moisture that had moved into the Northeast US, as shown below by the Blended Total Precipitable Water product (values in the 40-50 mm or 1.6-2.0 inch range) and the Blended Total Precipitable Water Percent of Normal product (with values in excess of 200%).

Blended Total Precipitable Water product [click to enlarge]

Blended Total Precipitable Water product [click to enlarge]

Blended Total Precipitable Water Percent of Normal product [click to enlarge]

Blended Total Precipitable Water Percent of Normal product [click to enlarge]

The hourly evolution of moisture was depicted by the MIMIC Total Precipitable Water product (below).

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

Tropical Storm Bret

June 19th, 2017 |

GOES-16 “Veggie” Band (0.86 µm) animation of Tropical Storm Bret, 1545-2030 UTC on 19 June 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

The fast-moving tropical system in the southern Caribbean Sea has developed a closed circulation and has been named Bret.  Tropical Storm Bret, shown above in an animation of GOES-16 Near-Infrared (0.86 µm) imagery that highlights land/water contrasts (the Orinoco River in Venezuela and Caribbean Islands — some with cloud streamers in their lee — north of Venezuela stand out clearly), is forecast to remain very close to the South American coastline.  Such proximity to land will likely hinder development. Further, wind shear in the atmosphere over the storm is predicted to increase.

Bret is embedded within a ribbon of very moist air (associated with the ITCZ) that stretches from Africa to the northwest Caribbean, as shown in the animation below (taken from this site) that shows morphed microwave observations of total precipitable water.

Microwave estimates of Total Precipitable Water for the 24 hours ending 1900 UTC on 19 June 2017 (Click to enlarge)

For more information on Bret, refer to the National Hurricane Center and the CIMSS Tropical Cyclones sites (where you can also follow the future of the system emerging into the Gulf of Mexico).

Atmospheric river events bring heavy precipitation to California

January 13th, 2017 |

MIMIC Total Precipatable Water product [click to play MP4 animation]

MIMIC Total Precipatable Water product [click to play MP4 animation]

A series of 3 atmospheric river events brought heavy rainfall and heavy snowfall to much of California during the first 10 days of January 2017 (NWS San Francisco/Monterey | WeatherMatrix blog). Hourly images of the MIMIC Total Precipitable Water product (above; also available as a 33 Mbyte animated GIF) showed the second and third of these atmospheric river events during the 06 January11 January 2017 period, which were responsible for the bulk of the heavy precipitation; these 2 events appear to have drawn moisture northeastward from the Intertropical Convergence Zone (ITCZ)..

Terra MODIS Visible (0.65 µm) and Near-Infrared

Terra MODIS Visible (0.65 µm) and Near-Infrared “Snow/Ice” (2.1 µm) images [click to enlarge]

A relatively cloud-free day on 13 January provided a good view of the Sacramento Valley and San Francisco Bay regions. A comparison of Terra MODIS Visible (0.65 µm) and Near-Infrared  “Snow/Ice” (2.1 µm) images (above) showed that snow cover in the higher terrain of the Coastal Ranges and the Sierra Nevada appeared darker in the Snow/Ice band image (since snow and ice are strong absorbers of radiation at the 2.1 µm wavelength) — but water is an even stronger absorber, and therefore appeared even darker (which allowed the areas of flooding along the Sacramento River and its tributaries to be easily identified). A similar type of 1.6 µm Near-Infrared “Snow/Ice” Band imagery will be available from the ABI instrument on the GOES-R series, beginning with GOES-16.

Better detail of the flooded areas of the Sacramento River and its tributaries was seen in 250-meter resolution false-color Red/Green/Blue (RGB) imagery from the MODIS Today site — water appears as darker shades of blue, while snow appears as shades of cyan (in contrast to supercooled water droplet clouds, which appear as shades of white). In the corresponding MODIS true-color image, rivers and bays with high amounts of turbidity (tan shades) were evident; the offshore flow of sediment from a few rivers could also be seen.

Terra MODIS true-color and false-color RGB images [click to enlarge]

Terra MODIS true-color and false-color RGB images [click to enlarge]

 

Late-season Tropical Storm Otto in the southwest Caribbean Sea

November 21st, 2016 |
ascatwinds_1433utc_21nov2016

Metop-A Scatterometer winds at 1430 UTC and GOES-13 10.7 µm Brightness Temperature (Click to enlarge)

A late-season tropical depression has formed in the southwestern Caribbean Sea. The morning Metop-A pass on 21 November 2016 allowed ASCAT scatterometer winds to be sampled over the system: rain-flagged values near tropical storm force were present as shown above. A similar image (from this site) is available here, and also here (from this site).

GOES-13 Infrared (10.7 µm) Brightness Temperatures (Click to animate)

Infrared (10.7 µm) imagery from GOES-13, above, from 1315 through 1715 UTC on 21 November, shows periodic deep convection over the Depression; the grey regions in the deepest convection over the system correspond to brightness temperatures colder than -75 C. The environment surrounding this system, shown below, is marginally favorable for strengthening; sea-surface temperatures are warm, although the oceanic heat content suggests the warmth does not extend through a deep column of water. Wind shear over the storm is modest (but far stronger north of the storm). (Imagery below is from this site). The system is forecast to become a tropical storm within the next 24 hours.

Sea-surface temperatures, Oceanic Heat Content and Wind Shear (Click to enlarge)

Update: Otto was named a tropical storm at 2100 UTC 21 November; GOES-13 Visible (0.63 µm) Imagery is shown below. Numerous tropical overshooting tops can be seen during the course of the day.

GOES-13 Visible (0.63 µm) Imagery on 21 November 2016 (Click to animate)

MIMIC Total Precipitable Water fields, below, show that Otto emerged from a region of persistent deep moisture over the southwestern Caribbean Sea that has been contracting as the storm formed. This region of moisture was focused along the intersection of a stalled and decaying Atlantic frontal zone and the Pacific monsoon trough (hourly animation).

MIMIC Total Precipitable Water fields at 2100 UTC on 17,18,19,20 and 21 November (Click to enlarge)

DMSP-16 Microwave (85 GHz) imagery, below, showed evidence of a closed eye associated with Otto at 2132 UTC.

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

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