Hurricane Fernanda

July 17th, 2017 |

GOES-16 Visible [0.64 µm, top) and Infrared Window (10.3 µm, bottom) images [click to play animation]

GOES-16 Visible [0.64 µm, top) and Infrared Window (10.3 µm, bottom) images [click to play animation]

* 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 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).

GOES-16 Infrared Window (10.3 µm) images [click to play animation]

GOES-16 Infrared Window (10.3 µm) images [click to play animation]

Mesoscale Convective Vortex over Arizona

July 17th, 2017 |

Terra MODIS Infrared Window (11.0 µm) image, with SPC storm reports of severe winds plotted in cyan [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with SPC storm reports of severe winds plotted in cyan [click to enlarge]

* 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.

GOES-16 Infrared Window (10.3 µm) images, with station identifiers plotted in yellow and SPC storm reports plotted in cyan [click to play animation]

GOES-16 Infrared Window (10.3 µm) images, with station identifiers plotted in yellow and SPC storm reports plotted in cyan [click to play animation]

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.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly surface reports [click to play animation]

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.

SPC Mesoscale Discussion [click to enlarge]

SPC Mesoscale Discussion [click to enlarge]