Dew as rain predictor

[midlf]

The spouse heard somewhere that dew in the morning means no rain in the forecast and dry in the morning indicates rain. Our location is SE Wisc. Anyone ever heard this before? She has been keeping track the last few weeks and so far it's somewhat reliable.

 

[deereguy]

I heard the same thing from a golf course sup. They used the theory to know whether to turn on the irrigation or not that day.

It seems to be a very predictable method.

 

[jbrumberg]

midlf:

I pasted the definition of dew that I got from Googling. I am a certified weather geek, but not a meteorologist. I am/was a certified weather watcher. There is an element of truth to the "rule". The key to dew formation is the radiational cooling effect which is most prominant during cloudless cold nights which is typical of a good strong high pressure weather system that usually means good weather . I have been scrutinizing the weather for over thirty years and I think the "Dry Rule" holds an element of truth for the reasons I mentionned. I do not support the "Dry Rule" just for the reasoning that the same conditons paired with wind and/or a very low dew point high pressure system will inhibit dew formation.

dew, thin film of water that has condensed on the surface of objects near the ground. Dew forms when radiational cooling of these objects during the nighttime hours also cools the shallow layer of overlying air in contact with them, causing the condensation of some water vapor.

Jay

 

[Amontilado]

Midl,

Never heard of that rule, but as with any "rule of thumb", it's in how it is applied. Dew forms with a very calm boundary (near ground) layer, even more calm than when fog forms. Down here on the "Guff"(Gulf) coast, we can have dew in the morning, but when the Gulf breeze comes onshore during the late spring into early fall, it may or may not touch off thunderstorms in one little piece of the world. It's just a part of the big equation.

Steve

 

[jbrumberg]

Midl,

Never heard of that rule, but as with any "rule of thumb", it's in how it is applied. Dew forms with a very calm boundary (near ground) layer, even more calm than when fog forms. Down here on the "Guff"(Gulf) coast, we can have dew in the morning, but when the Gulf breeze comes onshore during the late spring into early fall, it may or may not touch off thunderstorms in one little piece of the world. It's just a part of the big equation.

Steve

Amontilado AKA Steve:

I agree. Convective uplifting = thunderstorms and/or showers which are just thunderstorms that did not quite "make it". There are too many variables to make weather "Rules". "The Red Sky In Morning... Sailors Take Warning Rule" kind of applies better to the British Isles than the eastern US. Sun dogs and rings around the sun/moon, jet contrails becoming cirrus clouds are pretty accurate indicators of rains usually within 24 hours. I never could understand the old sailor Rule- "When the Sea Hawg Jumps... Man the Pumps" Jay

 

[Marine1]

If I have dew in the morning there will always be rain in my bathroom by noon.

Seriously though, the one about the moon's halo means rain in 24-48 hours seems to be fairly reliable in my neck of the woods.

Is there always dew in the desert because they don't get much rain there. I know it gets cold overnight so maybe. I don't know.

I'm just waiting for Global Room Temperature.

 

[rogdan]

I've heard this all my life and just believed it as passed down knowledge through generations of my family. I have never put it to the test though but we had no dew this morning and the forecast is for rain today (we need it).

 

[scott_vt]

The spouse heard somewhere that dew in the morning means no rain in the forecast and dry in the morning indicates rain. Our location is SE Wisc. Anyone ever heard this before? She has been keeping track the last few weeks and so far it's somewhat reliable.

Mornin Steve,
Gee thats possible, but I have heavy dew this morning and we are supposed to get thunder showers later on today !

Cant make heads or tails out of that !

 

[jbrumberg]

scott vt:

I had the same conditions this morning and had some T storm activity this afternoon as you. It's the high humidity and convective lifting dynamic. Your VT hills contribute to this as well. The sunlight "stirred things up" today. I love watching those cumulus clouds build up in the afternoon ! I really can not help myself when it comes to weather and unfortunately a few other things. Jay

PS: Any idea what a "sea hawg" is?

 

[rogdan]

I've heard this all my life and just believed it as passed down knowledge through generations of my family. I have never put it to the test though but we had no dew this morning and the forecast is for rain today (we need it).

The theory didn't hold water, no rain yesterday.