Case Study: 02 - 03 August 1997

• I. Introduction and SatRep Diagnosis for 02 August 1997/06.00 UTC
  • Introduction
  • Overview of satellite imagery for 02 August 06.00 UTC
  • Key parameters on isobaric surfaces for 02 August 06.00 UTC
  • Relative streams and conveyor belts for 02 August 06.00 UTC
• II. Development of Upper Level Low and Rapid Cyclogenesis
  • Introduction for Upper Level Low and Rapid Cyclogenesis
  • Very Short Range Forecast from 02 August 06.00 UTC - 18.00 UTC
  • Development of cloud configurations during Very Short Range Forecast
• III. Diagnosis for 03 August 1997/00.00 UTC
  • Overview of satellite imagery for 03 August 00.00 UTC
  • Key parameters on isobaric surfaces for 03 August 00.00 UTC
  • Relative streams and conveyor belts for 03 August 00.00 UTC
  • Summary
• IV. Diagnosis for 03 August 1997/06.00 UTC
  • Overview of satellite imagery for 03 August 06.00 UTC
  • Key parameters on isobaric surfaces for 03 August 06.00 UTC
• V. Very Short Range Forecast from 03 August 1997/06.00 UTC - 18.00 UTC
  • Introduction for Very Short Range Forecast
  • Development of cloud configurations during Very Short Range Forecast for 03 August 06.00 UTC - 18.00 UTC
  • Diagnosis for 03 August 18.00 UTC with parameters on isentropic surfaces

02 - 03 August 1997 - Relative Streams And Conveyor Belts For 03 August 00.00 UTC

03 August 1997/00.00 UTC - Meteosat WV image; position of vertical cross section indicated

In the image above a vertical cross section line is chosen which crosses the WV band at the rear side of the upper level low, the dry slot, the cloudiness over Ireland intensified by the PVA maximum in the left exit region of the jet streak and the southernmost part of the Warm Front Shield.

03 August 1997/00.00 UTC - Vertical cross section; black: isentropes (ThetaE), orange thin: IR pixel values, orange thick: WV pixel values

Isentropes and IR + WV pixel values show a typical upper level low situation around 55N/14W where a peak in the WV signal identifies the rear side of the Upper Level Low. The WV minimum around 53N/10W corresponds to the Dark Stripe, while the broad maximum to the south represents the Warm Front Shield. Isentropes show a Baroclinic Boundary of the Upper Level Low; isentropes of 322K and 330K represent surfaces respectively within and above this Baroclinic Boundary.

03 August 1997/00.00 UTC - Meteosat IR image; magenta: relative streams 322K - system velocity 268° 18 m/s, yellow: isobars	03 August 1997/00.00 UTC - Meteosat IR image; cyan: potential vorticity 330K, red: isobars for potential vorticity, magenta: relative streams 330K - system velocity 268° 18 m/s, yellow: isobars for relative streams

Relative streams on these surfaces show a lot of typical features for both the Upper Level Low and Rapid Cyclogenesis. At the lower surface of 322K (left image) a rising stream over the British Isles from south-east to north-west is a typical phenomenon on low surfaces for Rapid Cyclogenesis; however, the pronounced cyclonic circulation in the area of the Dark Stripe corresponds to the Upper Level Low. At the higher surface of 330K (right image) a typical frontal situation can be noticed over west Ireland with a strongly rising Warm Conveyor Belt accompanying the Warm Front Shield and the dry intrusion from north-west in the area of the Dark Stripe. This is again a situation which typically appears with Rapid Cyclogenesis.