“Stratospheric instrusion vortex” off the US East Coast

June 25th, 2009 |
GOES-12 water vapor images

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 June25 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

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

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

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

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

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

Canadian Fire and Ice

June 24th, 2009 |
MODIS 3.7 µm shortwave IR images

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

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 (R=visible; G=snow/ice; B=shortwave IR)

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-m resolution MODIS true color image

250-meter resolution MODIS true color image

Hurricane Andres

June 23rd, 2009 |
GOES-11 visible images

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

GOES-11 10.7 µm IR images

Lake Superior lake breeze

June 22nd, 2009 |
GOES-12 visible images

GOES-12 visible images

GOES-12 visible images (above) showed that a well-defined lake breeze developed along the western portion of Lake Superior during the afternoon hours on 22 June 2009. The MODIS Sea Surface Temperature (SST) product from 2 days earlier (below) indicated that SST values in the much of the middle of the lake were still in the low 40s F (blue color enhancement) — and Buoy 45006 was actually reporting a SST value of 39 F on 22 June. In northern Wisconsin, note the large surface air temperature gradient that existed between Port Wing (station identifier PNGW3) which remained in the upper 40s F and Ashland (station identifier KASX) which rose into the low 80s F!

MODIS Sea Surface Temperature product

MODIS Sea Surface Temperature product

Farther to the south, GOES-12 visible imagery also showed that a Lake Michigan lake breeze was moving inland across southeastern Wisconsin and northeastern Illinois (below).

GOES-12 visible image

GOES-12 visible image