Shannon Weather Radar Offline 14th-30th July

snaps

Strange today, heavy yellow spells of rain have swept over me today and we have had nothing, even the last 3 or 4 hours there has been constant yellow over us and nothing!

Oscar Bravo

Likewise here(Castlebar) snaps.showed rain(yellow spells too) all evening over here and its more or less dry.certainly no persistant rain.

weisses

Same here in Dingle

Su Campu

The rain this evening is being produced by an upper warm front at around 700hPa (~10,000ft), which lies well ahead of the main surface front. The radar may be picking up elevated precipitation which evaporates somewhat before reaching the surface.

Aiel

Forgive my ignorance but have to ask.Does the radar pick up drizzle no?I know drizzle is from very low cloud's so its possible it doesnt detect it.I just ask because its showed no cloud's over Galway all morning yet it couldnt be more grey,dull and damp here right now since very early this morning.

Deep Easterly

Aiel wrote: »

Forgive my ignorance but have to ask.Does the radar pick up drizzle no?I know drizzle is from very low cloud's so its possible it doesnt detect it.I just ask because its showed no cloud's over Galway all morning yet it couldnt be more grey,dull and damp here right now since very early this morning.

I have noticed that myself, that sometimes the radar does not pick up on drizzle. Maybe it is to do with the intensity. Drizzling like mad here all moring but not registering any great amounts.

The current radar:



is more likely showing where the drizzle is most intense.


As to sat pics, I could be wrong but I think the intensity of cloud showing on them is to do with the temperatue of the cloud tops. The whiter and more and dense the cloud looks on a sat pic the cooler the cloud is. That is why I think that thin wispy cirrus cloud can often look more threatening from above than low thick stratus which usually contained in a much warmer airmass.

WolfeIRE

steady drizzle all day here too. Miserable day.

Su Campu

The diameter of the drops plays a huge role in determining the radar's output, plus its sensitivity setting, etc. As drizzle droplets are by definition <0.5mm, they must fall below the radar's sensitivity.

People are describing damp, misty conditions, which would imply droplet diameters even much smaller again, hence the reason why they're not showing up.


Reflectivity perceived by the radar (Ze) varies by the 6th power of the rain droplets' diameter (D), the square of the dielectric constant (K) of the targets and the drop size distribution (e.g. N[D] of Marshall-Palmer) of the drops. This gives a truncated Gamma function, [13] of the form:

|K|2 N0e − Λ D D6dD Precipitation rate (R), on the other hand, is equal to the number of particles, their volume and their fall speed (v[D]) as:

R = N0e − Λ D (πD3/6) v(D)dD

odyboody

As a long time lurker I thought I had learnt a thing or 2 but those formulas hurt. Didn't understand them even slightly but my brain hurt just looking at them:o

Deep Easterly

odyboody wrote: »

As a long time lurker I thought I had learnt a thing or 2 but those formulas hurt. Didn't understand them even slightly but my brain hurt just looking at them:o

Don't worry, you're not the only one!!

https://www.youtube.com/watch?v=JqZo07Ot-uA

Su Campu

Well looks like we're not the only ones with radar issues.....Spain are missing 4 of their 14 radars!

Ciaran500

Some odd readings from it this morning

GSF

looks like the repairs didnt achieve the desired result

Aiel

Yep,i noticed that this morning too.It would be funny if it actually wasnt so serious.Like how it might affect farmers,pilots etc if it was heavier weather then that showing up,or not showing up, should i say.

Discodog

Ciaran500 wrote: »

Some odd readings from it this morning

Looks like a time lapse image bit like the star tracks that you get if you aim a camera at the Pole Star.

Parakeets

Curiously this noisy scan is useful for identifying where the cross-over line is between each adjacent radars in Donegal Bay and South Irish Sea, by observing the straight lines showing the cross over point. This shows which radar has priority at the interface.