weather warning
Posted: Tue Jul 04, 2006 7:51 am
protect them crops down south TORRO CONVECTIVE OUTLOOK issued at 1945GMT on Monday 3rd July 2006
VALID: Tuesday – Thursday 4th – 6th July 2006
Plume of moisture/instability will spread from the south across southern England and into South Wales through Tuesday and overnight into Wednesday, becoming slow moving for a time. This will occur in advance of upper vort max which will be lifting northwards from near Iberia to lie somewhere near the Brest Peninsula by midday Wednesday.
At the surface, a shallow area of low pressure will develop to the SW of the UK, with a further shallow low moving north-northeast from France. By Wednesday afternoon, a complex area of low pressure looks like lying across much of England and Wales.
Convective initiation and evolution is difficult, and tricky to pin down. At this stage it looks like scattered showers or storms will move into parts of SW England/cent-S England overnight tonight, and then continue north or north-west through the Midlands and Wales. Other storms may develop across these areas, and across parts of SE England through the afternoon, although lack of deep forcing looks like limiting the storm coverage. Deep-layer shear is predicted to be fairly low, and as such, any storms will be poorly organized, although could give brief hail to near severe limits, and gusty winds. In addition, torrential rain may lead to local flooding, and frequent cloud-ground lightning is possible.
Later in the day, and especially overnight, a cluster of storms looks like moving out of France into southern counties of England. Differences in model guidance means confidence is low on the areas expected to be impacted, but some frequent lightning and torrential rain is possible. ECMWF predicts a closed low-level circulation moving out of France into cent-S England later in the night and on Wednesday morning, before becoming stationary across the S Midlands. In addition, deep-layer shear is progged to increase across cent-S/SE England and E Anglia later in the night and on Wednesday, with 500 hPa SSE winds of 35 knots atop 850 hPa winds from the E at 15-20 knots, and surface winds from the east of 5-10 knots.
Should this occur, there are 2 areas of concern.
1) Given the depth and amount of moisture in the lower levels of the atmosphere (surface dew-points of 18-19C, 850 hPa dew-points of 10-12C), strong low-level convergence (due to the formation of 1 or more shallow low pressure areas) and deep lifting, very large rainfall totals are possible. ECMWF strongly indicates this, with 24 hour grid-point rainfall totals of over 100mm across Somerset, most of it after 12Z. Thus, parts of the West Country, SW England, cent-S England, SE Wales and the SW Midlands are at risk from flash-flooding, which could be quite widespread. In addition, storms are likely to be very electrically active, and bring marginally-severe hail, and gusty winds.
2) For eastern parts of Cent-S England, SE England, E Midlands and E Anglia – this region currently looks like missing the more widespread activity through the daytime on Wednesday. However, it also looks like kinematics may be sufficient for mesocyclones to form in any storms which do develop. Given the large amount of low-level moisture, and low-level vorticity, there is a risk of tornadoes during the day, in addition to large hail, gusty winds, frequent lightning, and locally torrential rain.
Of these 2 possibilities, the risk of substantial flash-flooding on Wednesday is, at this stage, the biggest concern, with Somerset, Dorset, Wilshire and Bristol the areas currently predicted to be most at risk. However, this is a complex and evolving situation, and attention should be paid to forecasts over the next few days. The risk areas are likely to change as the situation develops, as the various computer models are handling the development and evolution of the upper low somewhat differently.
If the situation remains favourable, CONVECTIVE DISCUSSIONS or WATCHES will be issued on this page.
FORECASTER: RPK
******PLEASE REPORT SEVERE WEATHER TO TORRO HERE********
VALID: Tuesday – Thursday 4th – 6th July 2006
Plume of moisture/instability will spread from the south across southern England and into South Wales through Tuesday and overnight into Wednesday, becoming slow moving for a time. This will occur in advance of upper vort max which will be lifting northwards from near Iberia to lie somewhere near the Brest Peninsula by midday Wednesday.
At the surface, a shallow area of low pressure will develop to the SW of the UK, with a further shallow low moving north-northeast from France. By Wednesday afternoon, a complex area of low pressure looks like lying across much of England and Wales.
Convective initiation and evolution is difficult, and tricky to pin down. At this stage it looks like scattered showers or storms will move into parts of SW England/cent-S England overnight tonight, and then continue north or north-west through the Midlands and Wales. Other storms may develop across these areas, and across parts of SE England through the afternoon, although lack of deep forcing looks like limiting the storm coverage. Deep-layer shear is predicted to be fairly low, and as such, any storms will be poorly organized, although could give brief hail to near severe limits, and gusty winds. In addition, torrential rain may lead to local flooding, and frequent cloud-ground lightning is possible.
Later in the day, and especially overnight, a cluster of storms looks like moving out of France into southern counties of England. Differences in model guidance means confidence is low on the areas expected to be impacted, but some frequent lightning and torrential rain is possible. ECMWF predicts a closed low-level circulation moving out of France into cent-S England later in the night and on Wednesday morning, before becoming stationary across the S Midlands. In addition, deep-layer shear is progged to increase across cent-S/SE England and E Anglia later in the night and on Wednesday, with 500 hPa SSE winds of 35 knots atop 850 hPa winds from the E at 15-20 knots, and surface winds from the east of 5-10 knots.
Should this occur, there are 2 areas of concern.
1) Given the depth and amount of moisture in the lower levels of the atmosphere (surface dew-points of 18-19C, 850 hPa dew-points of 10-12C), strong low-level convergence (due to the formation of 1 or more shallow low pressure areas) and deep lifting, very large rainfall totals are possible. ECMWF strongly indicates this, with 24 hour grid-point rainfall totals of over 100mm across Somerset, most of it after 12Z. Thus, parts of the West Country, SW England, cent-S England, SE Wales and the SW Midlands are at risk from flash-flooding, which could be quite widespread. In addition, storms are likely to be very electrically active, and bring marginally-severe hail, and gusty winds.
2) For eastern parts of Cent-S England, SE England, E Midlands and E Anglia – this region currently looks like missing the more widespread activity through the daytime on Wednesday. However, it also looks like kinematics may be sufficient for mesocyclones to form in any storms which do develop. Given the large amount of low-level moisture, and low-level vorticity, there is a risk of tornadoes during the day, in addition to large hail, gusty winds, frequent lightning, and locally torrential rain.
Of these 2 possibilities, the risk of substantial flash-flooding on Wednesday is, at this stage, the biggest concern, with Somerset, Dorset, Wilshire and Bristol the areas currently predicted to be most at risk. However, this is a complex and evolving situation, and attention should be paid to forecasts over the next few days. The risk areas are likely to change as the situation develops, as the various computer models are handling the development and evolution of the upper low somewhat differently.
If the situation remains favourable, CONVECTIVE DISCUSSIONS or WATCHES will be issued on this page.
FORECASTER: RPK
******PLEASE REPORT SEVERE WEATHER TO TORRO HERE********
More harm than good if we don't get some more!
