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]

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