GOES-12 visible images

GOES-12 visible images (above) showed a nice example of convective initiation along an outflow boundary from thunderstorms a few hours earlier across northeastern Iowa on 25 June 2009. This new convection that developed along the outflow boundary produced hail of 1.5 inch in diameter and damaging winds in extreme northern Illinois (just south of the Wisconsin border) during the 20:42 -21:02 UTC period.

A comparison of AWIPS images of the MODIS visible channel and a Red/Green/Blue (RGB) composite using MODIS bands 01/07/31 (below) showed the value of the false-color RGB imagery to help highlight the darker green patch of wet ground produced by heavy rainfall from the initial area of thunderstorms. Ice crystal clouds appear as varying shades of pink in the RGB image, which also helps to identify growing areas of cumulus clouds that have glaciated.

The next generation of AWIPS (AWIPS2) should offer NWS forecasters the ability to create and display this type of 24-bit RGB imagery (which is not possible using the 8-bit graphics capability of the current AWIPS system).

MODIS visible + false-color RGB image

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GOES-12 water vapor images

A small “dry swirl” feature (yellow color enhancement) was seen on AWIPS images of the GOES-12 6.5 µm water vapor channel (above) off the East Coast of the US on 24 June – 25 June 2009.

A comparison of a GOES-12 water vapor image with the corresponding GOES-12 sounder Total Column Ozone product at 21:00 UTC on 24 June (below) confirmed that this was a small-scale “stratospheric intrusion vortex”, with ozone values greater than 370 Dobson Units (lighter green color enhancement) in the vicinity of the dry feature on the water vapor imagery.

GOES-12 water vapor + GOES-12 sounder Total Column Ozone product

An overlay of GFS40 model fields on GOES-12 water vapor and Total Column Ozone images (below) indicated that the dynamic tropopause (taken to be the pressure of the PV1.5 potential vorticity surface) was as low as the 400 hPa level at 12:00 UTC on 25 June.

GOES-12 water vapor image + GOES-12 sounder Total Column Ozone product

A more detailed view of the vortex could be seen using 1-km resolution MODIS 6.7 µm water vapor images (below).

MODIS water vapor images

A comparison of MODIS water vapor, IR window, and visible images (below) showed that there was a lack of high clouds with this stratospheric intrusion vortex — only low-level clouds existed over the region in the vicinity of the vortex.

MODIS water vapor + IR + visible images

A comparison of a MODIS water vapor image with 1-hour MADIS satellite winds and GFS40 400 hPa height (below) showed that the stratospheric intrusion vortex was located just to the northeast of the closed low that was off the US East Coast during the period.

MODIS water vapor image + satellite winds + GFS 400 hPa height

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MODIS 3.7 µm shortwave IR images

Wildfire activity was beginning to increase across parts of Quebec, Canada on 24 June 2009 — and AWIPS images of the MODIS 3.7 µm shortwave IR channel (above) revealed a number of large fire “hot spots” (red to yellow color enhancement) that were increasing in areal coverage between 16:29 UTC and 18:14 UTC.

According to the CIMSS Wildfire ABBA product (below), some of these fires were hot enough to saturate the 3.9 µm shortwave IR sensor on GOES-12 (yellow fire pixels).

GOES-12 Wildfire ABBA product

In addition, false color Red/Green/Blue (RGB) images using the MODIS visible channel, the 2.1 µm near-IR “snow/ice” channel, and the 3.7 µm shortwave IR channel (below) also showed that during the 105 minutes between the 2 MODIS images there was a significant amount of southward displacement to the ice that remained in the northern half of James Bay — ice in the bay (as well as glaciated ice crystal clouds) exhibited varying shades of pink in the RGB image, in contrast to areas of open water (darker blue colors) or supercooled water droplet clouds (varying shades of white).

MODIS RGB images (Red=visible; Green=snow/ice; Blue=shortwave IR)

A 250-meter resolution MODIS true color image from the SSEC MODIS Direct Broadcast site (below) showed even more detail in the ice floes in James Bay, as well as some new smoke plumes from fires that had begun to burn in far eastern Ontario.

250-meter resolution MODIS true color image

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GOES-11 visible images

Hurricane Andres (briefly) became the first hurricane of the Eastern Pacific tropical cyclone season on 23 June 2009. However, the satellite presentation of Andres was rather unremarkable: even though a low-level “eye” circulation was recognizable on GOES-11 visible images from the CIMSS Tropical Cyclones site (above), the GOES-11 IR cloud top temperatures (below) were quite warm over the center of the Category 1 hurricane due to the fact that deep convection was displaced well to the south. However, a small convective burst could be seen developing along the southern periphery of the low-level circulation center on the final visible image at 20:00 UTC.

GOES-11 10.7 µm IR images

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