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

On 15 July Hurricane Fernanda became the first Category 4 tropical cyclone of the 2017 Northern Hemisphere season. GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of a well-defined eye during the period of rapid intensification. As the National Hurricane Center mentioned, it was unusual to have a hurricane of this intensity at such a low latitude in the Eastern North Pacific Basin.

#Fernanda is among strongest hurricanes in the East Pacific at such a low latitude (<12°N). 100 kt at 10.9°N! @UMiamiRSMAS @capitalweather pic.twitter.com/nVJm622tE6

— Brian McNoldy (@BMcNoldy) July 14, 2017

Fernanda fluctuated between Category 3 and Category 4 intensity during the 15-17 July period (ADT | SATCON) as it passed over the warm waters of the East Pacific Ocean (Sea Surface Temperature and Ocean Heat Content) — and trochoidal oscillations in the northwestward motion of the eye could be seen in GOES-16 Infrared Window (10.3 µm) imagery (below).

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

Strong summer monsoon season thunderstorms developed over Arizona in the pre-dawn nighttime hours on 17 July 2017, producing damaging winds across the Phoenix area (SPC storm reports). A Terra MODIS Infrared Window (11.0 µm) image (above) revealed cloud-top brightness temperatures as cold as -77ºC at 0508 UTC.

GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed the development and eventual dissipation of the overnight convection.

During the following daytime hours, GOES-16 “Red” Visible (0.64 µm) images (below) displayed the circulation of a Mesoscale Convective Vortex (MCV) as it propagated west-southwestward across southern Arizona. Note that surface dewpoint temperatures were in the upper 60s to low 70s F across southern Arizona, an indicator of the monsoon moisture that was in place across the region. The MCV appeared to play a role in helping to force the development of new thunderstorms later in the afternoon in the vicinity of the Arizona/Mexico border.

On the previous evening, a Mesoscale Discussion from SPC (below) mentioned the presence of weak deep-layer wind shear over the portion of Arizona affected by these nighttime severe thunderstorms — MCVs often form in such a low-shear environment.

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

Strong morning thunderstorms with a few severe weather reports, and abundant heavy rain (24-h totals ending 1200 UTC on 12 July 2017, from here), spread over the northern part of the GOES-16 default western Mesoscale Sector on the morning of 12 July 2017. The animation above shows the GOES-16 Advanced Baseline Imager (ABI) 10.3 µm imagery with Geostationary Lightning Mapper (GLM) Lightning Flash event locations superimposed, at 1-minute timescales. The top of the default Mesoscale Sector cuts through central Wisconsin.

Click here to see a graphic with the GLM Flashes for the 3 different hours.

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A comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images on 12 July 2017 (above; courtesy of William Straka, SSEC) shows the large iceberg (named A-68) that had separated from the Larsen-C ice shelf in Antarctica (Project MIDAS).

===== 13 July Update =====

A 12 July vs 13 July comparison of VIIRS Infrared Window and Day/Night Band images (below) revealed a slight expansion of the ice fracture, as Iceberg A-68 slowly drifted away from the Larsen-C ice shelf.

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