View Full Version : temperature inversion

12-17-2006, 03:59 PM
the air temps have been unusually mild as of late, and unusually inverted. *normally the air cools with increasing altitude. *an inversion occurs when the air at the surface is cooler than the air above it. *this occurs most nights when the cooler air settles in the valleys. *if there is enough humidity, fog *will form there. *this situation usually reverses shortly after daybreak as the surface warms, the fog clears, and the surface again becomes warmer that the air above.

we have had some days during the last week where the surface temps failed to rise enough to break this inversion, mostly because we have been under the center of a strong dome of high pressure. *byron has noted in his fishing report today that the temps failed to reach the predicted high. *

i usually fish the elk, a tailwater with lots of generation, in which the water temp is not affected as much by air temps. *i was able to fish thursday, and again yesterday. *i did catch a few, but noticed that the fish were much less active than normal.

i was wondering if anyone has studied the effects of temperature inversion and fish activity. *if there is an effect there it might even suggest the opposite case, *i.e. very unstable air like that which precedes a frontal passage would increase fish activity.

i used to keep up with air stability indices when i flew gliders. *i haven't checked them for a while now, but they are probalby readily available. *maybe this could be an alternative predictor for when the cows are in the barn. * ;)

Byron Begley
12-17-2006, 06:28 PM

Thank you so much for explaining this and bailing me out. I thought I was going nuts. Like I said this morning I was ready to turn this fishing report over to the Easter Bunny. Maybe I should add Air Stability Indices to the report.


12-17-2006, 08:40 PM
Wow...that makes perfect sense. I've been following the water temp online the last few days, and after a promising start, it leveled off, and actually dropped on, I believe, Friday. You hear about inversions all the time in places like Los Angeles, but they can happen anywhere - we even get them here in south Louisiana, where of course there is no mountain/valley situation. I think we had one the other day, when the fog never did quite burn off all day.

12-18-2006, 11:29 AM

i think i can say that most everyone on this board will agree that your report is first class. *this information combined with the other member's posts of their actual experiences is an invaluable resource. *so why don't we leave the easter bunny to jelly beans and colored eggs...

i have heard for years from the seasoned fishermen here on guntersville lake that the fish get real active just before a front moves through. *i had never fished regularly enough to notice, nor did i think that much about it.

my interest in fly fishing for trout was rekindled this past summer, and i have since managed to average to get out about once a week. *the results of the last two outings were so different in terms reduced activity, i got me to thinking...

i live on the brow of sand mountain, overlooking the tennessee river, and wake up many a morning looking down on a beautiful fog laden valley. *this scene is generally short-lived as the fog will usually disipate within an hour or so of sunrise. *but on these strongly inverted days, *the valley stayed in fog well into midday, and even after the fog burned off you could see a definite haze or inversion layer there.

i don't know if this has a lot or a little to do with fish activity. *i really think there must be many factors that play into a good vs. slow day of fishing. *but i think i will start tracking air stability vs. success on the stream and see if there is a pattern. *

i did some research last night and the national weather service computes every day what they call the lifted index. *it is a single digit measure of air stability. a positive value indicates more stable air than baseline, and negative value means more unstable. *these values are based on the twice daily weather balloon soundings.

if there seems to be a correalation there, i'll let ya'll know and maybe we can use it. *thanks again for your report and this very fine forum for the sharing of information.


12-18-2006, 03:35 PM
I don't know about temperature inversion and all that stuff, but it has been my experience that the fish will eat more actively if bad weather is coming in. i think that they sense the change in barometric pressure and it scares them. They don't have the luxury of knowing if it is going to be a passing shower or a flood of biblical proportions so they figure it is going to be the worse and they eat like crazy to get ready for it. they also eat good when it is starting to rain. Not a downspour or flash flood, just a light steady rain, will make the fish eat more. i think it knocks more bugs into the water and that triggers a feading frenzie.

Green Weenie
12-18-2006, 03:54 PM
I agree. It seems like most game, be it fish, deer, birds, etc., move about and feed more just before or just after periods of drastic weather. I'm sure some of this is attributed also to the rapid variance in the barometric pressure. I think a similar thing happens when the generators are turned on or off on our favorite tailwaters. The fish feed ravenously with the falling or rising water.
This is some good stuff, guys. Keep it coming!

12-18-2006, 04:35 PM
I've never had much luck after a good rain. All the fish are full by then ;)

Byron Begley
12-18-2006, 06:44 PM
I don't know if you guys saw it in todays fishing report but I did some checking on air temperature this weekend. It was warmer or the same temperature at night at Mount Leconte (Elevation 6,400 feet) compared to Townsend (Elevation 1,150 feet). This has been an experience for me that I won't forget.


12-18-2006, 09:55 PM
I think there's only going to be a day or two more of these conditions - a front is going to push through. By the end of the week, we're supposed to have more "normal" temperatures for December...nothing super cold, but cool. Y'all will get pretty much the same conditions, probably a day later.

Today, here in the New Orleans area, extremely heavy fog, and it never completely lifted all day...very gloomy - like northern Europe in winter, and almost no wind.

12-18-2006, 10:54 PM
just a few days ago I was speaking with my father and he said he had some friends who were avid bass fishermen and they swore by fishing right before a front moved in. he also said that if the wind is coming in from the east (blowing west) the fishing will be dead. "when the wind is from the east, fishing is least. when the wind is from the west, fishing is best"

12-18-2006, 11:57 PM
when the wind is from the east, fishing is least. when the wind is from the west, fishing is best"

I've heard that phrase before, too...and it might apply to freshwater. But down here in our marsh, a west wind is the kiss of death; it tends to blow the clean, salty water out of the marsh and replace it with low, muddy water. Any wind out of the east or southeast is best for us, but that is a peculiarity of geography, with the Mississippi greatly influencing conditions.

Generally, the fish turn on before a front moves through, and afterwards, they tend to clam up.

12-19-2006, 03:03 AM
The weathermen around Louisville tell us that on a still day, the coldest time of the day is 30 minutes after sunrise. This is because the ground warms from the sunlight. The coldest air is about 100-200 above the surface. When the warmed air rises it displaces the cold air and temperature inversion occurs. This is why fog often occurs at daybreak on still days.

Why lake bass feed before bad weather is simply from the food chain disruption. Heavy clouds = no sunlight. No sunlight=no alge bloom. No alge bloom=no food for the shad and alge eaters. Shad activity then slows and fish activity slows. Takes 12 hours of blue bird skies to start the alge bloom again then fishing activity returns. In the meantime use crawfish patterns they don't feed as much on alge eaters and live shad.