Potential Vorticity (PV) anomaly aiding convective development

July 2nd, 2013 |
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

AWIPS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the development of pockets of thunderstorms across Iowa, eastern Nebraska, and northwestern Missouri  on 02 July 2013.  Several of these storms produced hail up to 1 inch in diameter (SPC storm reports).

Note the pronounced cyclonic spin across the region of thunderstorm development — this was due to the approach of a compact shortwave trough that was rotating around the western periphery of a larger-scale upper-level trough of low pressure that was centered over the middle Mississippi River valley on that day. This shortwave trough had a nice signature on GOES-13 6.5 µm water vapor channel images (below; click image to play animation).

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

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

GOES-13 sounder Total Column Ozone product

GOES-13 sounder Total Column Ozone product

In addition, the GOES-13 sounder Total Column Ozone (TCO) product (above; click image to play animation) revealed that a distinct maximum in TCO values (red color enhancement) accompanied this disturbance. NAM40 model overlays of the pressure of the Potential Vorticity (PV) 1.5 surface (a general indicator of the height of the dynamic tropopause) suggested that a PV anomaly was associated with the high TCO values (below) — and this PV anomaly was likely helping to dynamically force some of the development of thunderstorms seen across the region.

GOES-13 sounder Total Column Ozone product with NAM40 PV 1.5 pressure and 500 hPa geopotential height

GOES-13 sounder Total Column Ozone product with NAM40 PV 1.5 pressure and 500 hPa geopotential height

Potential Vorticity anomaly approaching Baja California and Southern California

November 5th, 2019 |

GOES-17 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm) and Air Mass RGB images, with and without contours of PV1.5 pressure [click to play animation |MP4]

GOES-17 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm) and Air Mass RGB images, with and without contours of PV1.5 pressure [click to play animation |MP4]

GOES-17 (GOES-West) Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm) and Air Mass RGB images (above) displayed the signature of dry, ozone-rich air associated with a Potential Vorticity (PV) anomaly approaching Baja California and Southern California on 05 November 2019. The “dynamic tropopause” — taken to be the pressure of the PV1.5 surface — descended to the 500 hPa level within this PV anomaly.

A GOES-17 Water Vapor image with plots of available NOAA-20 NUCAPS soundings (below) is labeled with sounding points within the core of the PV anomaly (Point 1) and within the core of the driest air (Point 2).

GOES-17 Upper-level Water Vapor (6.2 µm) images, with plots of available NOAA-20 NUCAPS soundings [click to enlarge]

GOES-17 Upper-level Water Vapor (6.2 µm) images, with plots of available NOAA-20 NUCAPS soundings [click to enlarge]

The NUCAPS sounding profiles for Point 1 and Point 2 are shown below. The middle/upper troposphere was quite dry at both locations.

NUCAPS sounding profile for Point 1 [click to enlarge]

NUCAPS sounding profile for Point 1 [click to enlarge]

NUCAPS sounding profile for Point 2 [click to enlarge]

NUCAPS sounding profile for Point 2 [click to enlarge]

Potential Vorticity anomaly over the East Pacific Ocean

January 29th, 2019 |
GOES-17 Air Mass RGB images [click to play animation | MP4]

GOES-17 Air Mass RGB images [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 Air Mass RGB images from the AOS site (above) showed the characteristic signature of a Potential Vorticity (PV) anomaly over the East Pacific Ocean on 29 January 2019. A descending tropopause brought ozone-rich air from the stratosphere down to very low altitudes — and this ozone-rich air was highlighted by deeper shades of red (the Air Mass RGB uses the 9.6 µm Ozone band to calculate the Green component). A Gale Force low became better organized beneath this PV anomaly, quickly reaching it’s occluded stage (surface analyses).

The deepening midlatitude cyclone also exhibited a vivid signature on GOES-17 Mid-level Water Vapor (6.9 µm) imagery (below). An overlay of the GFS75 model PV1.5 pressure — a parameter commonly used to diagnose the level of the “dynamic tropopause” — showed values as low as 800 hPa at 18 UTC.

GOES-17 Mid-level Water Vapor (6.9 µm) images, with and without contours of GFS75 model PV1.5 pressure [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images, with and without contours of GFS75 model PV1.5 pressure [click to play animation | MP4]

Strong potential vorticity anomaly off the California coast

February 9th, 2010 |
GOES waver vapor imagery + PV1.5 pressure + 500 hPa geopotential height

GOES waver vapor imagery + PV1.5 pressure + 500 hPa geopotential height

A strong potential vorticity (PV) anomaly was propagating southeastward just off the California coast on 09 February 2010 — and this feature had a striking presentation on AWIPS images of GOES-11 water vapor channel data (above), with a pronounced arc of very dry air (yellow color enhancement) seen around the periphery of the circulation. According to the CRAS model fields, the tropopause (taken to be the pressure of the PV1.5 surface) was being brought downward as low as the 600 hPa pressure level within the core of the PV anomaly.

Images of the GOES-11 sounder Total Column Ozone derived product (below) depicted ozone values as high as 430 Dobson Units (red color enhancement) in the vicinity of the PV anomaly, supporting the idea that the tropopause height was very depressed within the circulation feature.

GOES sounder Total Column Ozone + PV1.5 pressure + 500 hPa geoptential height

GOES sounder Total Column Ozone + PV1.5 pressure + 500 hPa geoptential height

=================================

GOES-11 Sounder and Imager water vapor channel images

GOES-11 Sounder and Imager water vapor channel images

A 4-panel comparison of the three water vapor channels on the GOES-11 Sounder (6.5 µm, 7.0 µm, and 7.4 µm) and the GOES-11 Imager 6.7 µm water vapor channel (above) showed that the dry air signature was even quite evident on the Sounder 6.5 µm channel (darker blue color enhancement, upper left panels) — this particular water vapor channel weighting function normally peaks quite high in the atmosphere (around 325 hPa), where these types of water vapor gradients and signatures are usually not as well-defined.

However, due to the dry air within the middle to upper troposphere associated with the PV anomaly, the weighting functions of all 4 of the GOES-11 water vapor channels (calculated using rawinsonde data from Vandenberg Air Force Base) peaked at altitudes that were quite a bit lower compared to the more “normal” conditions that would be seen in a US Standard Atmosphere or USSA environment (below). Convection moving onshore across southern California that day was responsible for at least one sighting of a waterspout in the San Diego area, and inland precipitation amounts of 1.0 to 1.5 inch were widespread.

GOES-11 sounder and imager water vapor weighting functions (Vandenberg vs USSA)

GOES-11 sounder and imager water vapor weighting functions (Vandenberg vs USSA)