GOES-13 / GOES-14 visible channel image

The Atlantic Tropical Season’s seventh named storm, Gert, was southeast of the island of Bermuda on Monday August 15th on a projected path that keeps it well to the east of Bermuda. The morning full-resolution visible imagery (above) from GOES-13 (left) and GOES-14 (right) show a well-defined Central Dense Overcast through which are penetrating a few overshooting tops. These tops are far more easily visualized with the more oblique viewing angle afforded by GOES-14 (overhead at 105º West Longitude vs. 75º West Longitude for GOES-13). AVHRR Infrared Imagery from NOAA-16 shows brightness temperatures below -75º C with the coldest of the overshoots.

GOES-13 Enhanced Infrared and Observed Shear

Gert is at present in a region of small shear, as shown in the analysis above taken from the CIMSS tropical weather website. However, the projected path is towards higher shear. Strengthening to hurricane status may be difficult because of the increase in shear and because of progressively colder water along the projected path of Gert into the northern Atlantic. There has not yet been a hurricane season in the Atlantic during which none of the first 7 named storms — ‘A’ through ‘G’ — achieved hurricane status. (In 2002, Gustav was the first Hurricane after 6 Tropical Storms).

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The following appeared in the Area Forecast Discussion issued by the National Weather Service forecast office at State College, PA on the morning of 12 August 2011:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
523 AM EDT FRI AUG 12 2011

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
HIGH PRESSURE AND ASSOCIATED DRY AIR MASS PRODUCING A NEARLY CLOUDLESS MORNING OVER CENTRAL PA. 07Z MODIS 11-3.7UM IMAGERY SHOWS FOG HAS DEVELOPED IN THE VALLEYS OF WESTERN PA…WHERE COOL AIR IN CONTACT WITH RELATIVELY WARMER RIVER/STREAM WATER. ANY FOG SHOULD BURN OFF BY 8-9AM.

AWIPS images of the 1-km resolution MODIS fog/stratus product along with the corresponding 4-km resolution GOES fog/stratus product image (below) demonstrated the improvement in river valley fog detection that is possible with higher spatial resolution. Note the river valley fog on the MODIS image that was mentioned across western Pennsylvania, as well as other areas of river valley fog across parts of southern New York and northern West Virginia.

1-km resolution MODIS and 4-km resolution GOES fog/stratus product images

About 3 hours later, a similar comparison of 1-km resolution POES AVHRR and 4-km resolution GOES fog/stratus product images (below) show that river valley fog had increased across parts of western and northern Pennsylvania. The large amount of noise on the GOES fog/stratus product made it difficult to accurately locate where river valley fog features had formed.

1-km resolution POES AVHRR and 4-km resolution GOES fog/stratus product images

CIMSS participation in GOES-R Proving Ground activities includes making a variety of POES AVHRR and MODIS images and products available for National Weather Service offices to add to their local AWIPS workstations. Currently there are 49 NWS offices receiving MODIS imagery and products from CIMSS.

The VISIT training lessons “POES and AVHRR Satellite Products in AWIPS” and “MODIS Products in AWIPS” are available to help users understand these products and their applications to weather analysis and forecasting.

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GOES-11 / GOES-14 / GOES-13 visible channel images

The NOAA GOES-14 satellite (positioned over the Equator at 105º West longitude) was brought out of on-orbit storage for a brief period of testing, beginning on 10 August 2011. A comparison of GOES-11 (GOES-West), GOES-14, and GOES-13 (GOES-East) visible channel images (above) shows the evolution of stratus clouds along the southern California coast and the immediate offshore waters of the Pacific Ocean on 10 August. The images are displayed in the native projection of each GOES satellite, so the cloud features appear slightly different due to the different viewing angles.

On the following day (11 August 2011), multi-panel images show data from all 5 channels of the imager instrument on the GOES-11, GOES-14, and GOES-13 satellites (below). Note that the older GOES-11 imager is the last operational GOES to have the 12.0 µm IR channel — this channel was replaced by the 13.3 µm IR channel on GOES-12 through GOES-15.

GOES-11 imager channel data at 12:45 UTC on 11 August 2011

GOES-14 imager channel data at 13:00 UTC on 11 August 2011

GOES-13 imager data at 13:15 UTC on 11 August 2011

An animation of GOES-14 visible channel images (below) shows the passage of the thunderstorm outflow boundary that ended the long string of 40 consecutive days with daily high temperatures of 100º F or higher at Dallas/Fort Worth, Texas — the high temperature there only reached 97º F on 11 August.

GOES-14 visible channel images centered over Dallas/Fort Worth, Texas

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GOES-13 Visible with Airplane Positions

Turbulence associated with a developing line of convection over the Atlantic Ocean east of Florida was severe enough on August 9th to cause five injuries on a Miami-to-Washington DC flight and force an unscheduled landing of the 737-800 aircraft in Charleston, SC. The GOES-13 image, above, shows the path that the aircraft took through a line of developing convection east of Florida (Click here for a flash-based animation). The time that the satellite was scanning the region east of Florida was between 1935 and 1936 UTC (the nominal time of the image, 1932 UTC, refers to the first line scanned in by GOES-13; it takes almost 5 minutes to completely scan North America. See this NESDIS website for the normal scanning schedule).

Animations of visible imagery, 10.7-micrometer infrared imagery, and 6.5-micrometer infrared imagery (the so-called ‘water vapor channel’) all show a similar evolution, namely strong thunderstorms at the coast of Florida at the start of the loop followed by the development of a line of thunderstorms northeastward. It is through this developing line that the airline penetrated. (The flight path is here).

GOES Satellite data are routinely monitored to detect both the initiation of convection, and the presence of Overshooting Tops and Thermal couplets, the latter two features being well-correlated with severe weather and turbulence. Detection suffers, however, because of the relatively poor spatial and temporal resolution afforded by routine GOES scanning. What was detected on this day?

Overshooting tops were detected over the Florida peninsula at 1715 UTC and at 1732 UTC. The top at 1732 UTC is quite apparent in both the visible and infrared loops. Overshooting tops were not detected in the area again before the turbulence event, but their detection prior to the event suggests an airmass with the potential for strong convective development.

Convective Initiation (CI) was flagged along the southwest-to-northeast line of developing convection at 1832 UTC and 1845 UTC, roughly an hour before the turbulence event. (See this link for all Blog Posts on Convective Initiation). Note that the CI detection in this case — occurring — means that glaciation of the clouds has started. CI is drawing the eye to the convective towers that are growing most rapidly; therefore, their tops cool most quickly. It is to these growing cells that a forecaster must pay attention, particularly when they appear in an environment that will sustain overshooting tops.

(Here is an article on this flight from The Aviation Herald).

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