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Heavy Rainfall and Flood Watch February 2014


ZONE 51

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Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

Looking like a day of widespread chained heavy showers, these lasting into and overnight tonight, some large totals are possible some showers prolonged with a risk of flooding or increased flood problems.

 

Some areas missing the worst not everyone getting the downpours or at least not to many.

 

The orange zones (on my alert map) are the high risk areas for the largest accm rain, but not all of the covered zones expected to get the heavy rain totals, within the orange zones some areas seeing up to 20mm, but possibly more and up to 30-40mm perhaps a few spots up to 60mm, this most likely over east of Scotland but perhaps the west of Wales to.

 

My alert map is based on the accumulated model data but also the areas wheres most persistent showers are indicated. Have done an orange in areas possibly affected by 30-60mm of rain, the lower end of this amount more likely than the higher end.

 

Areas that could see the heaviest rainfall and accumulated ppn:

 

Parts of Central Southern, the SE, SW, Wales, the East of Scotland, these zones could see the highest totals up to 6am Wednesday of 20-30mm possibly 30mm+ and up to 60mm (the higher amounts are local totals not widespread)

 

Have also highlighted other areas with a Watch for up to 20mm but mostly10-15mm more likely though, rain/ppn areas most at risk from this are covering most of England and Wales, other areas of Scotland and Shetland. 

 

post-11361-0-72841200-1390895491_thumb.p

 

Some thundery, possibly sleet, hail. some snow for Scotland.

Edited by ElectricSnowStorm
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Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

Just a quick post not time now but lots going on over the next few days. For today widespread spells of showery rain and some prolonged/persistent rain at times, some of the rain heavy. The heaviest rain looks likely over the east of Scotland and probably central Scotland too with some large ppn totals here. Some persistent rain for the SE and it's over Kent that some of the highest falls of rain are indicated but also a pulse of large accumulations over the southeast Dorset area from a line of heavy persistent showers. So most places seeing some rain or showers some heavy downpours.

 

Sleet and snow likely in places especially the north, but also the south could get some sleet/wet snow mostly the higher ground though (at first...) 

 

Flood risk likely increasing in the worst affected zones due to the saturated ground it doesn't need much too increase the flooding. Generally rain/snow surface water a problem anywhere due to saturated ground especially the south which is most likely to have flooding more easily for this reason or increased flooding, but also the east of Scotland. Rivers and streams likely rising faster with smaller amounts of rain or snow than would normally be the case, and great concern for the days ahead with the threat of wind and rain storms but also intense shower type downpours.

 

My Alert map to highlight the accumulated ppn/rain up to 6am Thursday. 

post-11361-0-07521000-1390982269_thumb.p

I have also stated on the map that some sleet and snow could fall within the alert/watch areas, but please note as this is a ppn accm map that is based on the blue charts not snow charts snow could fall out of the alert areas where lighter accumulated ppn is indicated but not enough for rain alert!

Edited by ElectricSnowStorm
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Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

Apologies for not being able to update the thread, usually I do the rain maps with interest and have had to miss doing so due to throat infection, just to tired and weak to do a forecast. But if I did you could probably imagine a lot of yellow even orange/amber on the map!

Edited by ElectricSnowStorm
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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

Yesterdays rain front was probably overplayed by the media, stalling and breaking up. By the time it crossed the middle of the country in the early hours, it was just showers and light rain.

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Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

Quick post just adding an alert map here, based on accumulated ppn up to Saturday midnight:

post-11361-0-88907500-1391707407_thumb.p

 

 

Smaller image size:

post-11361-0-31519400-1391707408_thumb.g

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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

Posted Image

Upper Avon at Lilbourbe now in flood and rising swiftly. Managed to get the car through 300m of flooded lane, bit hairy, wave was coming up bonnet at times!!

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  • 3 weeks later...
Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

Apologies for the lack of updates in this thread most of the chat/posts has been in the local threads and Atlantic storm threads and I was to unwell to post, to do the alert maps and forecasts.

 

Recent rain/wind events have very much been a lot to keep up with with everyone involved in the crisis, it must have been very hard work too for the forecasters, I had not seen so many warnings out so frequently. 

 

At this stage I'm not going to input to much and not the alert maps as before, although I might get back to doing them it may only be alert maps for southern counties due to not having time, it is a lot of work going through the model data and making forecasts when there is a lot of weather happening or is going to occur.

 

 

Posted Image

2215 Radar image.

 

 

 

A band of rain is moving east through the country along an occluded front with some heavy bursts, some gusty gales too.

This affects overnight and then tomorrow need to watch out for heavy downpours, EURO4 indicates some particularly heavy potent showers across the S-UK Tuesday.

Posted Image

0000-0300hrs.

 

Posted Image

0600-0900hrs

 

Accumulated ppn data up to 0000hrs (Tue night) from 3 models - 

 

EURO4:

Posted Image

 

GFS:

Posted Image

 

 

NAVGEM:

Posted Image

 

Possibly we could have increasing flood problems for some areas over the next 24-36hrs, the ground is very sensitive to rainfall, the ground is so saturated for many areas and the ground water so high surface flooding is likely to happen quickly and don't need a lot of rain to do this.

The water entering rivers very fast. Saturated ground is like when there is solid frozen ground or even hard dry ground nothing can absorb easily.

Edited by Tobor
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Posted
  • Location: Stanwell(south side of Heathrow Ap)
  • Weather Preferences: Thunderstorms, squally fronts, snow, frost, very mild if no snow or frost
  • Location: Stanwell(south side of Heathrow Ap)

There's a band of rain continuing crossing the country tonight some heavy with very gusty conditions or gales so some added local surface water could be an issue in places.

 

Keeping watch for some heavy showers Thursday but main concern is a potent small feature moving across the south Thursday night/Friday:

Posted Image

The problem from this low for south UK is rainfall (affecting England and Wales) sleet and snow is possible with the system and it is all precipitation falling onto saturated and flooded ground, if the snow does settle if it happens then so something rather different for the south, but also flood problems too, we could be looking at the SE flood zones being hit with quite a bit of precipitation through Friday and possibly Saturday but also other southern areas at risk:

Posted Image

The low could be pulling in more ppn over the SE and EA Friday night:

Posted Image

Early hours of Friday rainfall/snowfall could be affecting in this position from SE to Wales as shown by GFS here:

Posted Image

 

This is an upcoming cold spell so the rain will be cold the cold could turn that rain to sleet or snow with accm this most likely the hills, but even low levels could see some sleet/snow at least falling.

 

Thursday eve:

Posted Image

 

Early hrs Friday:

Posted Image

 

Friday Afternoon/eve:

Posted Image

 

The rainfall/ppn is a concern over the next few days, here is Euro4's accumulated ppn data up to Friday eve (18z +48) 

 

Posted Image

 

Up to 32mm being indicated by the model for parts of S-UK up to Friday evening . The track of the low not set in stone so expect amounts to change and locations affected. Stay tuned to the TV/Radio /web chat.

 

Flood risk probably increasing for some areas over the next few days, ground water and river flooding ,unfortunately. But the long term outlook using probability is that warmer more settled weather could arrive, the lovely blossom trees are out round here not that this is going to change the weather mind but at least to lets us know Spring is on the way and this can of course bring high pressure.. 

 

 

Tobor.

 

(if you don't know, I was ElectricSnowStorm)

Edited by Tobor
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Posted
  • Location: cleethorpes
  • Location: cleethorpes

thanks tobor that ties with the GFS I saw upto 6th march. 

 

How acurate are weather stations rain accumulation.  According models we should get no more than  9mm  yet according to my station we got 42.9mm in the night.  Has a rain rate of 18.0 mm/hr.

 

ps the volume worst area tracked further south than yesterdays forcast this meant my area got alot rain according met observation it also hanged for awhile too resulting heavy rainfall.

Edited by vladthemert
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Posted
  • Location: North York Moors
  • Location: North York Moors

thanks tobor that ties with the GFS I saw upto 6th march. 

 

How acurate are weather stations rain accumulation.  According models we should get no more than  9mm  yet according to my station we got 42.9mm in the night.  Has a rain rate of 18.0 mm/hr.

 

ps the volume worst area tracked further south than yesterdays forcast this meant my area got alot rain according met observation it also hanged for awhile too resulting heavy rainfall.

The overnight rain was certainly more than predicted with about 13mm here in the space of 3 hours.42.9mm seems a bit suspect though, could it have been spraying off something nearby in the wind?On wunderground Louth reports about 12mm 

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Posted
  • Location: cleethorpes
  • Location: cleethorpes

The overnight rain was certainly more than predicted with about 13mm here in the space of 3 hours.42.9mm seems a bit suspect though, could it have been spraying off something nearby in the wind?On wunderground Louth reports about 12mm 

 

Thats very likely as live high rise its hanging over the veranda  slightly out abit there maybe not enough gap from above does hang out 1 foot.  Could be getting rain could easily cascade during heavy spells causing false reading.  Maybe need oftset it but only had the machine 4 days.

 

I have this website to compare to see if it ties up can adjust when they update there data for today.

 

http://www.realweather.net/wxhistory.php

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

thanks tobor that ties with the GFS I saw upto 6th march. How acurate are weather stations rain accumulation. According models we should get no more than 9mm yet according to my station we got 42.9mm in the night. Has a rain rate of 18.0 mm/hr.ps the volume worst area tracked further south than yesterdays forcast this meant my area got alot rain according met observation it also hanged for awhile too resulting heavy rainfall.

The overnight rain was certainly more than predicted with about 13mm here in the space of 3 hours.42.9mm seems a bit suspect though, could it have been spraying off something nearby in the wind?On wunderground Louth reports about 12mm

Yeah, I agree, that seems rather excessive, the total has got skewed somehow.The 24hr accumulative map gives a fairly good idea on the largest totals. :)post-15177-0-20713600-1393497289_thumb.p Edited by Mapantz
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