Growing up and living here in Southern California one of the best jobs you can have, in my opinion, is being a weather forecaster mainly because it’s almost the same weather here all year long with an average air temperature of around 72 degrees. What an ideal job! But all kidding aside, we do get some good, cold winter storms roll in from northwest from time to time and we have some years where we get what is called an “El Nino” season where it will rain hard every two to three days from January until April due to unusually warm ocean water around the equator pushing to the north. These storms are normally warm and loaded with moisture and, when they mix with cold air loaded with ice from the northwest, the warmer air will melt the ice high in clouds and pull a large percentage of the water out of the clouds making fishing very interesting.
So, first let’s begin by looking at the true definition of weather: The atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation. In the world of fishing weather it’s one biggest driving forces that make fish move in the water columns from deep to shallow water and vice versa. Fish always look for stable conditions. One of the reasons for this is the way they mentally map out an area where they’re going to hunt, feed, or spawn and when the water level drops, or rises quickly, or weather changes drastically, most fish will back off and suspend and wait till these situations stabilize before they will begin to remap a hunting, feeding, or spawning area. So when you have a really cold-air winter storm start to move in, you’ll notice a change in how the fish start to act and feed. There are two factors at play here: barometric pressure and low-light conditions.
Barometric pressure is an atmospheric pressure as indicated by a barometer and the atmosphere is basically just air surrounding the earth. When you have water in the atmosphere you have low pressure which will be measured by a barometer. The more water that’s in the air, the lower the barometer reading will be and so on. So whenever you look up and see a blue sky, this is a high pressure light-air condition and when you look up and see clouds in the sky this is a low-pressure condition with lots of water and ice floating in the sky. But, due to Earth’s gravity, these clouds have weight and want to fall towards the earth. And what determines the weight of the clouds are their size of the clouds and elevation. The higher in elevation the cloud is in the sky, the more the water molecules in the top of the clouds freeze and sink down towards the earth. This frozen water really weighs the cloud down. So when we get a cold storm from the north-west, with hundreds of miles of clouds packed together that are high in elevation, it’s like a freight train in the sky that has carts loaded with water and ice and as it moves closer to land you start to see the barometer readings drop. This is how it all begins in our world of fishing in relation to cold air and atmospheric pressure on the water.
So now we have this huge mass of cold and wet air that we call a storm moving towards the lake. The atmosphere is being pushed which creates heavy atmospheric pressure in front of the storm which is shown by a drop on the barometer. As a result, the fish, which use an internal swim bladder system that gives them the ability to control buoyancy and stay at different water depths, begin to feel the affect of this pressure that is in front of this cold air storm rolling in. The swim bladders are internal and filled with an oxygen gas mixture. The less gas that’s in the bladder will allow the fish to sink and with more gas in the bladder the fish will rise. The swim bladder is much like our lungs except most fish cannot expel the gas out as quickly as we can let air out of our lungs. This means that the fish needs time to slowly absorb the gas from the swim bladder to the outer glands. And as a fast moving cold storm approaches, the fish feel the pressure on their bladder first due to the added water pressure resulting from the increase in atmospheric pressure on the water. This increase in pressure starts to compromise the fish’s buoyancy in the water and starts to make the frustrated fish move to shallower areas to help relieve some of the added water pressure on their swim bladder.
To better understand this situation, if a fish is suspended in a lake is sitting at around 20 feet using it’s swim bladder for buoyancy, it has adjusted and is comfortable sitting at 20 feet with 20 foot of water weight pressure above it. But ,when you quickly add atmospheric pressure like a storm moving in and putting added pressure on top of the water, this adds to the water weight above the fish which makes the fish very uncomfortable. The fish will then start moving around and trying to find relief from this new added water pressure. In a few hours or more, the fish can start to adjust and absorb some of the bladder gas and find some relief from the new pressure rolling in overhead by the approaching storm. So, as you can see in this huge game of adjustments, which is change in a fish’s environment and will put the fish on the move until it can find some stability which may take some time for the fish to adjust to.
Now with lots of suspended fish getting frustrated and moving toward the shallows to find some relief from the pre-frontal conditions the bigger the fish the more affected it is. I have seen some monster fish move up shallow swimming around in just a couple of feet of water and most of the time these fish are very aggressive and easy to catch. I have found the pre-frontal dropping barometer window that will push fish shallow to be very small and length depends on how cold the approaching storm is along with the storm size and speed. But typically where I live the pre-frontal fishing window is around 3-6 hours and then the fish seem to adapt and adjust to the new atmospheric pressure overhead.
The other factor of having clouds overhead is the low-light condition. Fish love to hunt and feed under low-light conditions. Hunting out of a shadow is much easier than on a bright sunny day condition where small fish tend to hide until there are low-light conditions. The one factor you need to pay attention to after a storm has arrived is to look for stable conditions. If a storm rolls in and you get 2-3 days of steady clouds and rain, the fish will adapt after about 48 hours. But as soon as anything changes drastically, all bets are off and the fish will go back to a holding pattern till conditions stabilize. This is by far a very frustrating time as a fisherman because every atmospheric disturbance is a mixture of things and tend to always be just a bit different than any other before it. So finding tiny windows like in a pre-frontal falling barometer, or when the storm stalls over your area for a few days and conditions stabilize where you can find small productive fish catching windows where the fish are willing to bite is all part of the challenge of paying attention to change. Knowing how to read a barometer and understanding what kind of storm is in the atmosphere is all part of the homework you need to do to understand when and where you need to be.
But here in Southern California, we get the majority of our storms throughout the year from the West or Southwest and these storm are built off warmer waters so the clouds are thinner and warmer with no ice at the top of them. These storms tend to stretch for hundreds of miles and since the density of lower, warmer, thinner clouds is less they won’t push the barometer readings as low and these storms tend to be slower moving also so the fish have plenty of time pre-frontal to adjust to a slower change in the atmosphere. What I normally look for with type of weather is the shallow low-light condition. Typically the weather is very steady and the fish have had plenty of time to adjust and are in the shallows hunting and feeding. This has historically for me been a great time for a swimbait mid-depth (5′-10′) or on the surface. I have had some great times under theses conditions and landed some giant bass.
Some storms are packed with winds from all different directions and, once again, the rule of stable conditions in the fishing world applies. The fish will ride out the winds and wait for conditions to stabilize offshore suspended and as soon as the conditions stabilize the fish will start to move shallow and explore the inshore areas once again and begin their hunting and feeding ritual.
I have found that even on clear blue sky during a high-pressure weather pattern that the fish will look for stable conditions and once again if the weather stays in a stable pattern for more than 48 hours you can start to pattern the fish and find them to be much more predictable in their daily migration routes from deep to shallow water and vice versa and now it’s more about the timing of their movements with low-light conditions along with the moon, and sun phases.
So next time you watch the news and see that the weather is changing you’ll know how to change with it and catch more fish.