Using MODIS SST’s for Sea Fog and Precipitation

During the cool season (late November through mid April) WFO Corpus Christi experiences radiational fog and sea fog.  The sea fog is a particular challenge to forecast, can persist for a few days and sometimes advects inland.  This type of fog can be a hazard in ship channels and affect wind farm operations during bird migration periods when the visibility is reduced to 1 mile or less.  It is generally understood that during inverted lower tropospheric conditions, and the advection of a milder air mass and higher dewpoints that sea fog can develop over the relatively cooler nearshore waters (upper 50s to mid 60s in this case).  During the period from December 12 to 14, 2009 such conditions developed over the bays and nearshore waters and resulted in persistent dense fog along the Coastal Bend and possibly extending out to the offshore waters of the Gulf of Mexico.

During the evening of December 12th sea fog (1/4 mile or less) rapidly moved inland along the Coastal Bend while a low-level warm front also produced periods of drizzle and low stratus across South Texas.  The fog was slow to dissipate during the morning hours on December 13th and persisted over the bays and nearshore waters.  During the early morning hours on December 14th, dewpoints rose into the 60s across the offshore waters and eventually into the lower 70s.  Dewpoints as high as the upper 60s reached into inland areas along the Coast on December 14th.  Sea fog continued to be an issue during this period and persisted until a cold front arrived on the morning hours of December 15th.

Leading up to and during the sea fog event, forecasters used the combination of  the 1-kmMODIS SST’s product and the animation of the GOES fog (image below) depth to help for their marine and coastal forecasts.  These products were considered for issuing a long duration dense sea fog advisory, extending advisories and for inland dense fog advisories.

GOES fog depth product loop from 1131 to 1230 UTC 13 December 2009.

An upper level weather disturbance arrived on December 16th and produced a widespread stratiform precipitation event resulting in 1 to 2 inches of rainfall in South Texas.  Of particular interest was the heavier convective cells that occurred across the nearshore waters.  This area of enhanced rainfall and a few cloud to ground lightning strikes was in a stationary low level coastal convergence trough and may have been fueled by the much warmer SST’s evident on the MODIS products (darker blue color in image below).  Forecasters used the MODIS product for analyses and short term predictions of this rainfall event.

MODIS 1-km composite SST image at 0700 UTC 16 December 2009.

KCRP base reflectivity loop from 1509 to 1820 UTC 16 December 2009.

One thought on “Using MODIS SST’s for Sea Fog and Precipitation

  1. Great post! These are both great uses of SPoRT products for coastal applications. The loop of the GOES fog product nicely shows the onshore migration of fog. These satellite products are especially helpful for gaining information over the data void Gulf. What other observations do you have over the Gulf that report fog and sky conditions? Is it just ship reports or do can you get this information from buoys, too?

    Additionally, the radar definitely appears to show the convective precipitation is developing right along the edge of the warmer waters as seen in the MODIS SSTs.

    Thanks for the post!

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