Tornado in central California

November 15th, 2015 |

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

An EF-1 tornado was on the ground for about 20 minutes near Denair (Local Storm Report | Facebook post) in central California on 15 November 2015. 1-km resolution GOES-15 Visible (0.63 µm) images (above) showed that clusters of small thunderstorms rapidly developed in an environment of instability along and just behind a fast-moving cold frontal boundary. The location of the tornado is indicated by a red “T” on the 2145, 2200, and 2211 UTC images. Very strong southwesterly winds aloft allowed the upwind portion of the highly-tilted thunderstorms to be brightly illuminated by the low sun angle of late afternoon in mid-November.

The corresponding 4-km resolution GOES-15 Infrared (10.7 µm) images (below) revealed that cloud-top IR brightness temperatures quickly cooled from -23º C at 2130 UTC to -42º C at 2200 UTC.

GOES-15 Infrared (10.7 µm) images [click to play animation]

GOES-15 Infrared (10.7 µm) images [click to play animation]

There was a 30-minute gap in GOES-15 coverage from 2100 to 2130 UTC (due to a full disk scan), but a comparison of 1-km resolution NOAA-19 AVHRR Visible (0.63 µm) and Infrared (10.8 µm) caught the very early growth of the tornado-producing storm at 2115 UTC (below). The cloud-top IR brightness temperatures were as cold as -23º C at that time, indicating a high probability that cloud glaciation had begun.

NOAA-19 Visible (0.63 µm) and Infrared (10.8 µm) images [click to enlarge]

NOAA-19 Visible (0.63 µm) and Infrared (10.8 µm) images [click to enlarge]

A timely overpass of the Suomi NPP satellite allowed a comparison of 375-meter resolution VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images during the time that the tornado was srill on the ground (below). Once again, the strong slant of the storms due to increasing wind speeds aloft allowed the western/southwestern sides of the thunderstorm clouds to be brightly illuminated on the visible image. The coldest cloud-top IR brightness temperature was -51º C (yellow color enhancement), which was just shy of the -53º C tropopause temperature reported on the Oakland rawinsonde report at 12 UTC.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared (11.45 µm) images [click to enlarge]

A VIIRS true-color image of the storm visualized using RealEarth is shown below. The actual satellite overpass time was around 2151 UTC.

Suomi NPP VIIRS true-color image [click to enlarge]

Suomi NPP VIIRS true-color image [click to enlarge]

GOES-15 sounder Lifted Index (LI) derived product images (below) showed the pockets of post-frontal instability over central California — LI values less than -4 C were seen (yellow color enhancement).

GOES-15 sounder Lifted Index derived product images [click to play animation]

GOES-15 sounder Lifted Index derived product images [click to play animation]

Updated Criteria for GOES RSO Calls

November 11th, 2015 |
<strong>GOES-13 Water Vapor (6.5 µm) infrared imagery with Day 1 Convective Outlook and rawinsonde 850 hPa and 300 hPa observations (Click to enlarge)</strong> (Click to enlarge)

GOES-13 Water Vapor (6.5 µm) infrared imagery with Day 1 Convective Outlook and rawinsonde 850 hPa and 300 hPa observations (Click to enlarge) (Click to enlarge)

The Storm Prediction Center has revised its criteria for initiating GOES Rapid Scan Operations (RSO) calls. Previously, RSO was automatically activated when a Moderate Risk (MDT) appeared in the SPC Day 1 Convective Outlook. On October 1st that was changed per a September email from SPC:

Starting October 1, the SPC Lead Forecaster will contact the NCO/SDM to request GOES RSO whenever a Day 1 Convective Outlook includes an ENH Risk area. Data from the first six months of 2015 suggests SPC would request RSO on approximately 10-20 more days compared to the current MDT Risk criterion. Activating RSO on a more frequent basis using the ENH Risk criterion would improve NWS forecaster situational awareness on convectively active days and help prepare users for much higher temporal frequency GOES-R data.

An Enhanced Risk was issued on 11 November 2015 as a strong extratropical cyclone was developing over the midsection of the country. The image above shows the GOES-13 Water vapor imagery from 1145 UTC on 11 November. A strong jet extends from the southwestern United States northeastward. On the previous day (10 November, at 12 UTC) Albuquerque reported 135-knot winds at 300 hPa (and no winds at all at 200 hPa as the balloon was lost to the tracker); at 00 UTC on 11 November, winds were 162 knots just above the 250 hPa level. Strong veering, indicating warm advection, is apparent over the mid-Mississippi River Valley. Low-level warm advection is forecast to increase as the extratropical cyclone intensifies.

Update: GOES-East began RSO at 1545 UTC on 11 November 2015 — a few image animations are shown below.

GOES-13 Water vapor (6.5 µm) images [click to play animation]

GOES-13 Water vapor (6.5 µm) images [click to play animation]

Of particular interest on 6.5 µm water vapor imagery, above, was the tightly-wrapped signature of the middle-tropospheric vorticity center moving northeastward along the Kansas/Nebraska border.

GOES-13 Infrared (10.7 µm) images [click to play animation]

GOES-13 Infrared (10.7 µm) images [click to play animation]

The 10.7 µm Infrared images, above, showed the development of thunderstorms across Iowa which exhibited cloud-top IR brightness temperatures in the -50 to -60º C range (yellow to red color enhancement). Hail, damaging winds, and tornadoes were produced by these areas of deep convection (SPC storm reports).

GOES-13 Shortwave Infrared (3.9 µm) images [click to play animation]

GOES-13 Shortwave Infrared (3.9 µm) images [click to play animation]

3.9 µm Shortwave Infrared images, above, displayed numerous “hot spots” (black to yellow to red color enhancement) due to fire activity in parts of northeastern Oklahoma and southeastern Kansas.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

Finally, 0.63 µm Visible channel images, above, showed the hazy signature of smoke plumes from these Kansas/Oklahoma fires (along with a separate plume of blowing dust). In addition, as clouds cleared along the western edge of the storm, swaths of fresh snow cover could be seen over portions of Wyoming, Colorado, South Dakota, Nebraska, and Kansas. As much as 12.5 inches of snow was reported in northeastern Colorado, with wind gusts of 75 mph creating blizzard conditions.

40th Anniversary of the “Edmund Fitzgerald Storm”

November 10th, 2015 |

NOAA-4 daytime and nighttime Infrared composites [click to enlarge]

NOAA-4 daytime and nighttime Infrared composites [click to enlarge]

Today marks the 40-year anniversary of the powerful Great Lakes storm that was responsible for the sinking of the SS Edmund Fitzgerald (which occurred on 10 November 1975). The image composites (above, courtesy of Jean Phillips, Schwerdtfeger Library) were constructed from daytime and nighttime overpasses of the NOAA-4 polar-orbiting satellite, and show the large cloud shield of the storm moving northeastward from the Great Lakes into eastern Canada during the 10-11 November 1975 period. The rapidly-intensifying nature of the storm can seen by comparing the 12 UTC surface analyses on 09 November and 10 November.

Since the first operational geostationary weather satellites (SMS-1 and SMS-2) were relatively new back in 1975, the CIMSS Regional Assimilation System (CRAS) model was utilized to generate synthetic Infrared (IR) satellite images to provide a general idea of what the satellite imagery might have looked like for this intense storm. The 48-hour sequence of synthetic CRAS IR images (below) shows the evolution of the model-derived cloud features at 1-hour intervals.

CRAS model simulated Infrared imagery [click to enlarge]

CRAS model simulated Infrared imagery [click to enlarge]

Additional information about this Edmond Fitzgerald storm can be seen on this website, as well as the NWS Marquette and this journal article.

A strong storm of similar character developed over the Upper Midwest and Great Lakes region on 9-11 November 1998. GOES-8 (GOES-East) Infrared (10.7 µm) and Water Vapor (6.7 µm) images of this 1998 storm are shown below (and are also available as YouTube videos). This storm set all-time minimum barometric pressure records for the state of Minnesota, with 962 mb (28.43″) recorded at Albert Lea and Austin in southern Minnesota. On the cold side of the storm, up to 12.5 inches of snow fell at Sioux Falls in southeastern South Dakota. Wind gusts were as high as 64 mph in Minnesota and 94 mph in Wisconsin.

GOES-8 Infrared (10.7 µm) images [click to play MP4 animation]

GOES-8 Infrared (10.7 µm) images [click to play MP4 animation]

GOES-8 Water Vapor (6.7 µm) images [click to play MP4 animation]

GOES-8 Water Vapor (6.7 µm) images [click to play MP4 animation]

Hurricane Kate

November 10th, 2015 |

GOES-13 Visible (0.65 µm) imagery (Click to animate) (Click to enlarge)

GOES-13 Visible Imagery, above, shows Tropical Storm Kate northeast of the Bahamas late in the day on 9 November. The storm is over a region of warm sea surface temperatures, below (imagery from the CIMSS Tropical Weather Site), in an environment of low shear. RapidScat winds show winds between 35 and 40 knots to the northeast of the storm center. The projected path is also shown, paralleling the East Coast before moving out to sea. The path takes the storm north of Bermuda as well.

Sea-surface Temperatures, Wind Shear, and near-surface Winds, 9 November 2015 (Click to enlarge)

Suomi NPP viewed the storm as well, shortly after noon on 9 November. The Visible (0.64 µm), near-infrared (1.61 µm) and 11.35 µm imagery are shown below. The 1.61 imagery shows darker returns over ice clouds because of absorption at that wavelength. The extensive cirrus shield over Kate’s convection (and along the East Coast is association with frontal system) is readily apparent. Water-based clouds, in contrast, are bright white in both the visible and near-infrared channels.

Suomi NPP Visible (0.64 µm), near-infrared (1.61 µm) and infrared (11.45 µm) at 1836 UTC, 9 November 2015 (Click to enlarge) (Click to enlarge)

ASCAT winds from 0230 UTC on 10 November (below) also show strongest winds on the northern and eastern sides of the storm.

METOP Scatterometer winds and GOES-13 Infrared (10.7 µm) at 0230 UTC 10 November 2015 (Click to enlarge)

Kate was upgraded to a minimal Hurricane at 0900 UTC on 11 November.