GOES-13 0.65 µm visible channel images (click image to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the cyclonic circulation of clouds and the convective bursts associated with the development of Tropical Storm Bret in the western Atlantic Ocean north of the Bahamas on 17 July 2011.

A morning AWIPS image of MODIS 11.0 µm IR channel data with an overlay of MetOp Advanced Scatterometer (ASCAT) surface winds (below) indicated a broad cyclonic flow with maximum velocities around 22 knots at 14:23 UTC.

MODIS 11.0 µm IR image + ASCAT surface scatterometer winds

Later in the day, a DMSP-18 SSMIS 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed that the deep convection was limited to the eastern semicircle of the tropical cyclone at that time, due to the presence of some westerly wind shear.

DMSP-18 SSMIS 85 GHz microwave image + deep layer wind shear

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GOES-13 10.7 µm IR images (click image to play animation)

AWIPS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed the progression of two long-lived Mesoscale Convective Systems (or “derechos”) on 11 July 2011 — one moving southeastward from the Dakotas and Minnesota, and another moving northeastward from Nebraska. These two MCS features were responsible for a large number of severe weather reports (SPC: 10 July reports | 11 July reports).

Note the elongated band of cirrus that developed  behind the departing MCS feature, curving across parts of Iowa, Nebraska, Kansas, and Colorado toward the end of the IR image animation above — this striated cloud band marked the location of a well-defined deformation zone. Areas of light to moderate turbulence aloft are often present in association with such deformation zones, as was seen by the number of pilot reports overlaid on a GOES-13 6.5 µm water vapor channel image at 17:45 UTC (below).

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

The GOES-13 sounder Total Precipitable Water (TPW) derived product (below; click image to play animation) showed that abundant moisture (TPW values of 50-60 mm or 2.0 to 2.4 inches, violet color enhancement) was in place ahead of the storms as they moved rapidly eastward.

GOES-13 sounder Total Precipitable Water product (click to play animation)

A closer view of GOES-13 10.7 µm IR images with overlays of the Automated Overshooting Top Detection product (below; click image to play animation) revealed a number of overshooting tops, with the minimum cloud top IR brightness temperature of -81ºC occurring over eastern Iowa at 09:45 UTC. The overshooting tops were very evident after sunrise on GOES 0.63 µm visible channel imagery, as they cast shadows upon the thunderstorm anvil tops below (11:45 UTC visible image + overshooting top detection product comparison).

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

A set of three comparisons of 1-km resolution POES AVHRR 10.8 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of improved spatial resolution for more accurate detection of the location and magnitude of the coldest cloud tops on severe thunderstorms. On the 08:22 UTC, 08:47 UTC, and 11:37 UTC POES AVHRR images, the coldest cloud top IR brightness temperatures were -84ºC, -90ºC, and -85ºC, respectively (the coldest GOES-13 IR brightness temperatures were -78ºC for all three of those times). Note that the apparent northwestward displacement of cloud features on the GOES-13 images is a result of parallax error due to the large viewing angle from the geostationary satellite.

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

Very strong surface winds were observed along and in the wake of the well-defined bow echo seen on radar — peak wind gusts included 74 mph at Dubuque, Iowa, 75 mph at Chicago Midway Airport, and 85 mph at Michigan City, Indiana. These strong winds created a seiche across southern Lake Michigan (Seiche Warning | NWS Chicago event summary), with oscillations in water levels seen at Calumet Harbor, Illinois, Milwaukee, Wisconsin, and Holland, Michigan.

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07 July 2011 marks the 5 year anniversary of CIMSS providing MODIS images and products for National Weather Service (NWS) forecast offices to add to their local AWIPS workstations (via LDM subscription). This important “Research to Operations” effort has been a cornerstone of the GOES-R Proving Ground project. As of July 2011, CIMSS has provided experimental MODIS imagery in real-time to 70 NWS sites across the US. Shown below are a few examples of the types of MODIS images and products that are being distributed.

MODIS 0.65 µm isible channel and 2.1 µm near-IR "snow/ice" channel images

A comparison of MODIS 0.65 µm visible channel and 2.1 µm near-IR “snow/ice channel” images (above) shows the values of the snow/ice channel imagery for locating areas of flooding across the upper Missouri River basin (water is a strong absorber at the 2.1 µm wavelength, so it shows up very dark on the images).

MODIS 3.7 µm and GOES-13 3.9 µm shortwave IR images

A comparison of 1-km resolution MODIS 3.7 µm and 4-km resolution GOES-13 shortwave IR images (above) demonstrates the value of improved spatial resolution for the detection of “hot spots (red to yellow color enhancement) associated with active fires that were still burning along the periphery of the Honey Prairie Fire in southeastern Georgia.

MODIS and GOES fog/stratus product images

A comparison of 1-km resolution MODIS and 4-km resolution GOES-11 fog/stratus product images (above) again shows the value of higher spatial resolution for identifying the edges of fog features along the California coast. Also note the appearance of ship tracks in the offshore stratus deck on the MODIS image.

MODIS 11.0 µm and GOES-13 10.7 µm IR images

A comparison of 1-km resolution MODIS 11.0 µm IR and 4-km resolution GOES-13 10.7 µm IR images (above) shows the improved depiction of transverse banding cirrus features (which are a signature of potential turbulence). There were a few pilot reports of light to moderate turbulence across that particular region of transverse banding.

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

A comparison of the 1-km resolution MODIS 6.7 µm and the 4-km resolution GOES-13 6.5 µm “water vapor channel” images (above) shows a much better depiction of the compact middle-tropospheric vorticity feature over Quebec, Canada.

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature product

On the previous day (06 July 2011), generally cloud-free conditions over the western Great Lakes allowed a nice view of the Sea Surface Temperature (SST) across that region — note that SST values were still as cold as 40.3º F over parts of Lake Superior (above). The corresponding MODIS 0.65 µm visible image showed a few well-defined lake breeze boundaries, as well as a thin northwest-to-southeast oriented plume of smoke from wildfires burning in Canada.

MODIS Total Precipitable Water, Lifted Index, K Index, and Total Totals products

4-km resolution MODIS products that might be useful for assessing the pre-convective environment include the Total Precipitable Water, Lifted Index, K Index, and Total Totals products (above).

MODIS Cloud Phase and Cloud Top Temperature products

Other 4-km resolution products include the Cloud Phase and Cloud Top Temperature products (above).

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GOES-11 0.65 µm visible and 10.7 µm IR images (click image to play animation)

Strong thunderstorm outflow winds (gusting as high as 69 mph) created a severe dust storm (or “haboob“) in the Phoenix, Arizona area around 02:00 to 03:00 UTC on 06 July 2011 (or 7pm to 8pm local time on 05 July 2011), restricting the surface visibility to near zero with blowing dust and forcing a 45-minute Ground Stop at Phoenix Sky Harbor Airport (an interesting YouTube video of the approaching dust storm is available here). The Phoenix National Weather Service forecast office published a summary of the event, and additional information and 3D radar animations are available on the AccuWeather WeatherMatrix blog. A high-resolution GOES image can be found at the NOAA Environmental Visualization Laboratory.

McIDAS images of GOES-11 0.65 µm visible channel data during the day and GOES-11 10.7 µm IR channel data at night (above; click image to play animation) show how the Mesoscale Convective System over Arizona on 05 July evolved into a Mesoscale Convective Vortex (MCV) on the following morning over the deserts of southern California, as the cirrus canopy of the convective system eroded to reveal the mid-level circulation. The MCV then appeared to play a role in helping to initiate new convective activity over California later in the afternoon on 06 July.

AWIPS image comparison from 18:00 UTC on 06 July

MCVs maintain their structure through the release of latent heat associated with condensation when clouds form and especially when precipitation forms. This release of heat alters the stability of the atmosphere, inducing the formation of a cyclonic potential vorticity anomaly. MCVs erode when they encounter high wind shear.

An AWIPS image comparison (above) shows GOES visible channel data (the seam in the middle of the images demarcates data from GOES-11 or GOES-West and GOES-13 or GOES-East; note that the older GOES-11 data is darker because of the age and degradation of that satellite’s visible sensors), GOES 10.7 µm IR channel data, the Blended Total Precipitable Water (TPW) Percent of Normal product, and 850-300 hPa layer wind shear from the GFS and RUC models. In the present example, the MCV exists in an axis of low values of 850-300 hPa wind shear, as noted by model forecasts from the RUC and from the GFS. Abnormally high values of precipitable water are also present, exceeding 200% of normal according to the ‘Blended Product’ that combines observations from the GOES Sounder and ground-based GPS stations. Rawinsonde reports from Phoenix (00 UTC and 12 UTC on 06 July) and from Yuma (12 UTC and 14 UTC on the 06 July) show abundant moisture and relatively low shear. All of these data show environmental conditions that support MCVs.

GOES-11 Sounder TPW and LI derived product images

In the pre-convective environment across southern Arizona on 05 July, GOES-11 Sounder derived product images (above) showed Total Precipitable Water (TPW) values in the 40-50 mm (1.6 to 2.0 inch) range, and Lifted Index (LI) values as low as -5º to -8º C.

MODIS 11.0 µm IR image + negative and positive cloud-to-ground lightning strikes

As the MCS continued to move westward across Arizona, an AWIPS image of 1-km resolution MODIS 11.0 µm IR data at 05:33 UTC (above) showed cloud top IR brightness temperatures as cold as -72º C (black color enhancement), along with numerous negative and positive cloud-to-ground lightning strikes. At that time, the thunderstorm outflow winds were moving through Blythe, California (station identifier KBLH) producing wind gusts of 46 knots (52 mph) with a reduction in visibility to 1.5 miles, and also through Yuma, Arizona (station identifier KNYL) producing wind gusts of 40 knots (46 mph) with a reduction in visibility to 1.25 miles.

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