Dry, still weather really ought to help your protag escape the wolves. Moisture catches scent (puddles, dew on grass, etc) and the smell will pool there (stinky bacteria love skin rafts and water). Also, lack of wind will not push the scent particles around much making tracking more difficult. Alternately, a heavy storm would make tracking virtually impossible. What time of day or night might be important, too, but if the air's hot, dry, and not moving much that should be enough to help your protags.
I'll give you a few ideas about how scent works, then you can work what you want into your story and ignore what you don't. If you get to something and aren't sure, let me know. When you're ready, I'd also be happy to beta read your scene to look for logistical issues, if you like.
That said, if your group splits up, that will help the odds. I think that your protag running atop roofs is a great idea. It should confuse most of the dogs for quite a while anyway, so long as none of them actually see him and bust him that way. They might catch his scent, but it would be so diluted from distance and height that they would have a hard time pinpointing him, unless he stops for any length of time.
Remember, the longer any of your characters stay in one place, the stronger their scent will be there. So, say you hide someone in an alcove, their scent will get stuck there for hours after. If you stuff them in a closet with a closed door, the scent will seep under the door, but it will be much more difficult for the dog, because it will have to have proximity to the door in order to detect the scent. Once it does though the smell will be so strong, there won't be any shaking the animal.
Unfortunately for your protags, an abandoned urban environment will be free of human scent meaning that the character's scent will be very easy to pick up for the wolves.
Rule of thumb - scent moves like smoke. Watch it slide over pavement, then get tangled in grass and bushes. Something to think about when you're moving your characters around. The more "props" the more the scent will get caught and pooled.
Quick lesson on how (we think) scenting works for dogs. Dogs follow essentially two scents - ground (or what comes off your
shoes exactly where you step - that's bloodhound territory, and generally the weaker scent) and "air-scent." Humans shed a downright creepy amount of particles off the top of their heads, which then flows like a cone outward with the wind, with the person as the "point". This is our strongest scent loss by far. So covering your protag's head well won't hide the scent entirely, but it should help a little. Lets just say, I
never remove my hat when I'm hunting.
We're not sure exactly how, but dog's can sense hormones very easily too. Example - if one of your characters is especially panicky (lots of adrenalin pumping through the system), that character will be particularly easy for your wolves to find, and downright distracting from other calmer characters. Sweating heavily, breathing hard, and adrenalin all stink and your wolves
will find that
fast. A blood trail will also make it super easy (I'm sure the vamp would agree), so if any one is injured, they will have a particularly hard time.
If your character goes into water, the wolves will likely work it out, especially if he's under any physical duress. After he leaves, his wet footprints will be like a yellow brick road for them to follow, at least if the wolves are hot on his trail.
A word on wolves. I know these are "special" wolves, but a "natural" wolf will not want to split up to find their quarry. They are far weaker as individuals. Just something to consider when writing your scenes.
Also, all dogs, especially those with a high prey drive (like wolves) can not resist a chase. Its ingrained in their DNA. So if some character gets the bright idea to just run, they are so going down. There will be no outrunning the wolves unless they can get an obstacle between them. I'm not kidding, a fast-moving, shrieking "prey" kicks in a very primal instinct in predators and they just have to chase, unless their teeth are already sunk into something yummy. I thought that might spark an idea for you with this scene, so I wanted to share.
Hope some of that helps, and my meds haven't made my brain so fuzzy that only I think I'm making sense
. Please don't hesitate to ask more questions. Bad portrayals of wolves and dogs is a major peeve of mine, so I'd like to help however I can.
Also, in response to some earlier posts (too lazy to go looking for quotes: sorry) one of the reasons dogs make such excellent tracking machines is because they have the ability to single out an odor and mark it. They actually have a special compartment in their olfactory system just for that purpose (again, we think - there's still a lot human's just don't "get"). So smoke, coffee grounds, febreze, whatever will only confuse them for a few moments at best. Once they've imprinted a scent they can single it out with incredibly accuracy. While smoke and exhaust won't help them breathe by any means, it won't stop them either. It just makes their job harder.
As far as underwater HRD (human remains detection) goes, bodies release gasses as they decomp, which float to the surface, so that's what the dogs key in on as far as we know. After working with an HRD dog, I just can't bring myself to swim anywhere that white foam builds up in a river or lake. "Body foam" - gives me the heebie-jeebies.