The storm talk this weekend is probably nothing. The winter behind it is not

If you have seen the chatter about a tropical storm hitting Southern California over Labor Day weekend, the short version is that it is unlikely. The National Weather Service has it as the least likely of the outcomes on the table. A minority of models spin up a system off the coast of Mexico, most of them bring humidity and a small chance of showers, and that is about it. A tropical storm has to get a lot of things right in a row to make it this far north, and it usually does not.

So that is not the thing to plan around. The thing to plan around is what NOAA said about the winter two weeks earlier.

What the forecast actually says

The Climate Prediction Center has an El Niño Advisory in effect. In its 13 August discussion it put the odds of a very strong event through this autumn and winter at better than 90 percent, and gave a 69 percent chance that October through December finishes above 2.5 degrees Celsius above normal in the tropical Pacific. That would put it among the strongest on record going back to 1950.

Strong El Niño winters have tipped Southern California wetter before. It happened in 1982-83 and again in 1997-98, and those are the winters people still bring up when they talk about roofs failing all at once.

It is not a promise, though. The 2015-16 El Niño was one of the strongest ever measured, and Southern California still finished the season below average, the fifth dry year in a row. Researchers at Scripps later put it down to conditions in the Indian Ocean and western Pacific that shoved the storm track north into Oregon and Washington instead. NOAA is careful about this in its own wording: the chances of El Niño impacts are larger, but they are not guaranteed.

That is the honest position. A wet winter is more likely than usual. It is not certain. The sensible response is not to panic about it, and not to ignore it either. It is to spend an hour looking at your roof while the weather is still dry and the roofers still answer the phone.

Why this matters more here than the forecast suggests

Murrieta is a tile roof town, and tile fails in a way that hides itself. Concrete tile is a rain shield rather than a waterproof layer. The felt underlayment beneath it does the actual sealing, and felt has a much shorter life than the tile sitting on top of it. That is why a twenty year old roof can look perfect from the street and still let water into a ceiling. What you can see from the ground tells you very little about the layer that is doing the work.

Then there is how rain arrives here. The valley does not get weeks of steady drizzle. It gets most of its rain in a handful of concentrated storms, which means a roof that seemed fine in November can produce a brown ring on the ceiling in one afternoon in December. Small faults do not reveal themselves gradually. They wait for the first storm that drops an inch in a few hours.

The last piece is the order things happen in. The Santa Ana winds come before the rain, not after. By the time the first real storm arrives, the wind has already lifted tiles, worked at flashing around chimneys and skylights, and loosened things at the edges. The damage gets done in October and the consequences turn up in December, which is why so many people are surprised by a leak on a roof that was quietly damaged two months earlier.

What to look at now

Nearly all of this can be done from the ground with a pair of binoculars, and it should be. Walking on a tile roof breaks tile, so people who go up to check for damage often come down having caused some. Roofs are also the sort of place people fall from. If something needs a closer look, that is what a roofer with a ladder and the right footwear is for.

• Tiles that have slipped or cracked. Look for one sitting lower than the ones around it, a broken corner, or a gap where you can see dark felt underneath.
• The valleys. Where two roof planes meet, all the water from both of them funnels into one line. Valleys carry more water than anywhere else on the roof and they are usually where failed underlayment shows first. Leaves and needles sitting in a valley are worth clearing before the rain.
• Anything that pokes through the roof. Chimneys, skylights, vents and pipes are sealed with flashing, and flashing is exactly what wind pulls loose. Look for metal that has lifted, separated or rusted through.
• Flat and low slope sections. Patio covers and room additions are built differently from the tile field around them, and in practice they are often where the water is actually coming in. Standing water or bubbling on a flat section is worth a call on its own.
• Gutters and downspouts. A gutter packed with debris backs water up under the roof edge, which is a slow way to rot a fascia board. Check that downspouts still send water away from the foundation rather than against the wall.

Signs you already have a leak and have not noticed

Roof leaks rarely start with water dripping on the floor. They start quietly, and the early signs are easy to explain away.

• A faint brown or yellow ring on a ceiling or high on a wall, particularly one that has been there long enough that you have stopped seeing it.
• Paint that has blistered or a patch of ceiling texture that looks slightly swollen.
• A musty smell in a closet, a hallway, or the corner of a room that does not shift.
• Daylight visible through the roof boards from inside the attic, or dark staining on the underside of the sheathing.
• Insulation in the attic that is flattened or damp in one spot.

Attic staining is the useful one, because it shows up long before anything reaches the ceiling below. If you can get a torch into the attic safely, look at the underside of the roof near the valleys and around anything that penetrates the roof.

If you are going to call someone, call now

This is the same advice we give every autumn, and an El Niño forecast is just a stronger reason for it. Right now the winds have mostly done their damage and the rain has not started, so a roofer can get up there in dry weather, take photographs, and quote a repair properly.

In December that changes. Every roofer in the valley is triaging emergencies, the good ones are booked, and a repair that needed two hours in October becomes a tarp and a promise to come back. You also lose the ability to compare quotes, because when water is coming through a ceiling most people take the first available person.

One more thing worth saying plainly: a leak does not always mean you need a new roof. Often the underlayment has failed in one area and not generally, and a localized repair is the right answer. A roofer should be able to show you photographs of what they found rather than asking you to accept a replacement quote on trust. If the first thing you are offered is a full tear off without evidence, get a second opinion.

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