The area of convection that has been percolating within the Caribbean has acquired sufficient organization and speed to be named Tropical Storm Rafael (at 2100 UTC on 4 November, near the end of the animation, above, created at the CSPP Geosphere site). The storm is approaching the island of Jamaica where Tropical Storm Warnings are in effect.

1-minute GOES-16 Visible and Infrared images (above) showed Rafael as it intensified from a Tropical Depression to a Tropical Storm by 2100 UTC. Near the center of Rafael’s circulation there were periodic convective bursts (exhibiting cloud-top infrared brightness temperatures as cold as -88ºC), but there was very little GLM-observed lightning activity near the core of the tropical cyclone. Rafael was located just to the west of Buoy 42058, where the Sea Surface Temperature was 86ºF.

Rafael is currently in a region of warm sea-surface temperatures and low shear (imagery below is taken from SSEC/CIMSS’s tropical weather website), and slow strengthening is forecast as it moves between Jamaica and the Caymans en route to western Cuba.

The area of rich moisture that is supporting Rafael’s convection has been over the western Caribbean since late October. The animation for November of TPW from the MIMIC site (online archive) is shown below. Note, however, the relative dryness over the Gulf of Mexico, where Rafael is forecast to be by week’s end. The storm would have to overcome a significant amount of dryness to remain intense.

Advanced Clear-Sky Processor for Ocean (ACSPO) Sea Surface Temperatures from VIIRS, below, shown with I05 (11.45 µm) data (NOAA-20 data were downloaded at the CIMSS Direct Broadcast site and processed with CSPP software). Note the lack of convection over the Gulf of Mexico, and the water temperatures. Red in the SST enhancement below is approximately 80^oF. Shelf waters are relatively cool.

GOES-East airmass RGB imagery, below, shows Rafael developing within a moist airmass — that is, a green region within the RGB. As it moves northwestward, however, the environment becomes less favorable; this is indicated by regions with more orange. (Here is a Quick Guide on airmass RGB; here is another one)

===== Late 5 November Update =====

1-minute GOES-16 Infrared images (above) showed Tropical Storm Rafael as it intensified to a Category 1 Hurricane near the Cayman Islands at 0020 UTC on 06 November. Cloud-top infrared brightness temperatures associated with convective bursts near the center of Rafael were as cold as -91ºC; however, no GLM-detected lightning activity was seen with this convection during that 9-hour period.

A GOES-16 Infrared/Water Vapor Difference product (below) included an overlay of contours and streamlines of deep-layer wind shear. Rafael continued to remain in an environment of favorably low shear — and tropical overshooting tops that were likely penetrating the local tropopause were highlighted by increasingly negative values of the Infrared/Water Vapor Difference product (reference).

More information on Rafael is available from the National Hurricane Center. Interests in the northwest Caribbean and in the Gulf of Mexico should monitor the progress of this storm.

View only this post Read Less

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-19 (Preliminary/Non-operational) “Red” Visible (0.64 µm) images (above) — which showed thunderstorms that produced hail to 1.75″ in diameter, wind gusts to 94 mph and several tornadoes (SPC Storm Reports) across parts of North Texas. eastern Oklahoma and far northwestern Arkansas on 04 November 2024.

The corresponding 30-second GOES-19 “Clean” Infrared Window (10.3 µm) images are shown below. The coldest cloud-top infrared brightness temperatures associated with some these thunderstorms were -70 to -75ºC.

View only this post Read Less

NUCAPS estimates of temperature and dewpoint give swaths of information over the Arctic — a region where conventional observations are uncommon and widely spaced. The toggle above shows a disorganized low pressure system over central Alaska — light snow is widespread as shown by the surface observations, below (and in the toggle above).

The toggle above includes swaths of temperature and of relative humidity (derived from all NUCAPS profiles at that time) that are shown individually below. The color bar for 850-mb temperature has been modified so that temperatures of 0^oC and -10^oC are contoured in solid black. The >0^oC warmer region (yellow and red in the color curve) is south of the Aleutians. There is a relatively cold patch just northeast of the warm patch, and a stronger boundary between warmer and -10^oC and colder than -10^oC across central Alaska. There is good agreement between the NUCAPS analysis and the GFS analysis of 850-mb temperature at that time (here, from the TropicalTidbit website)

Kodiak Island is very near a region of dry air as indicated by the NUCAPS profiles; relative humidity in the 850-500 mb layer is <20% per the gridded NUCAPS analysis. The toggle below compares the NUCAPS profiles near Kodiak Island (a green profile, at 1323 UTC) with the 1200 UTC sounding at Kodiak. In this case the soundings tell similar stories: a largely dry atmopshere, and the diagnosed levels (FZL, -20^oC and -30^oC) are similar.

The NUCAPS swath also includes Fairbanks and Utqiagvik, both with 1200 UTC soundings. Comparisons at those two sites are shown below. NUCAPS near Fairbanks does capture the near-saturation in the snow-growth region of the atmosphere, and the tropopause height is in agreement; however, the low-level saturation and low-level inversion in the rawinsonde is not in the NUCAPS profile. If a forecaster had access to AMDAR/MADIS profiles from aircraft at the same time, that near-surface NUCAPS deficiency could be mitigated.

The comparison at Barrow/Utqiagvik, below, shows some similarities: the dry slot at mid-levels with relatively moist regions near the surface and below the tropopause. As you make the comparison between NUCAPS and rawinsondes, always recall the very coarse vertical resolution in NUCAPS profiles.

Gridded NUCAPS fields are also available at this SPoRT site, supplying views as shown below.

---

The SPoRT site above also contains microwave estimates of snowfall rate, derived using MIRS algorithms and (for the time shown) ATMS data from NOAA-20. Widespread light snow is indicated, as might be expected by the saturation in the snow growth region within the Fairbanks sounding.

Snowfall rate is also available at this UMD site where data from more satellites are available. Note the similarities in the two fields of snowfall rate from the two sites for the same overpass.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed thunderstorms that produced several tornadoes and damaging wind gusts (SPC Storm Reports) across parts of central Oklahoma on 03 November 2024. Pulses of thunderstorm overshooting tops exhibited 10.3 µm brightness temperatures as cold as -78.6ºC (brighter white pixels embedded within dark black regions) — and Enhanced-V cloud-top signatures were evident with some of the storms; the interior warm portion of the Enhanced-V signature (shades of red, in this particular color enhancement) often highlights where an Above-Anvil Cirrus Plume might be present.

1-minute GOES-16 GLM Flash Points depicted abundant lightning activity associated with these thunderstorms.

View only this post Read Less