those temperatures starting to climb on up. 80s and 90s. the other thing to watch wednesday, if you look closely, maybe some mountain thunder in the coastal range. dtw yao jailed in iran accused of spying. tonight, their fate. floods overwhelm part of one ash major city. the latest disaster in this record-breaking year. and sounding off. we'll meet the man who's never seen but often heard on the big screen. captions paid for by nbc-universal television

good evening. as we come on the air tonight, there are some fast-moving developments in libya where it appears rebel fighters have begun the battle for tripoli, what may be their final push to topple the government of moammar gadhafi. there had been reports of explosions and gunfire in the capital this evening. the fact he has not been seen is sure to fuel the questions about his whereabouts and his grip on power. let's get to our chief foreign correspondent in libya with the latest. >> reporter: good evening, lester. rebels started firing wildly in the air when they heard the reports that gadhafi had left the country. but even the rebels here do not know if those reports are true. what we can confirm, however, is that fighting has begun inside

tripoli itself in at least three neighborhoods after the rebels made major advances earlier today. after a week of some of the most intense battles of the six-month revolution against moammar gadhafi, today, a key victory. the u.s. and nato-backed rebels took control of all of the city of zawiya. the rebels have consolidated a base, just 30 miles from tripoli. when we arrived in zawiya today, the scars of the fighting were still fresh, buildings popped by bullets and partially collapsed, spent ammunition everywhere. and by our account, the bodies of at least five of gadhafi's sub-saharan african mercenaries on the ground. the center of zawiya has been taken by the rebels, the downtown area is destroyed. dozens of people have been killed. but this is a strategic area within striking distance of tripoli. the most intense fighting appears to have been at zawiya's

only hotel, the jewel. this hotel is one of the tallest buildings in zawiya. gadhafi sniper and mercenaries were using it as a base. to drive them out, the rebels fired mortars at the hotel and came storming through this door. the rebels have a renewed optimism. we'll be free. as we surveyed the damage, we saw a group of rebels, the same unit we followed on friday as they fought for this city. today they came to celebrate, libyan rebel style. a chaotic and somewhat dangerous barrage of anti-aircraft and automatic weapons fire. these fighters are convinced this war is nearing an end. the top rebel commander in this area has told us that the zero hour, the final battle for tripoli, has now begun. lester?

>> richard, thank you. andrea mitchell is our chief foreign affairs correspondent. she's in our washington bureau. andrea, what are you hearing there? and if the rebels are victorious, what would it mean for the u.s.? >> reporter: clearly, if they are victorious, it would vindicate the american and nato policy. the president is being briefed in martha's vineyard by one of his top national security officials, john brennan. but the u.s., of course, was initially slow to recognize the rebel government. this doesn't mean that all is good because there are concerns about their ability to control violence and to create a viable state. since recognizing them as the sole governing authority in libya and pouring money and weapons into the fighting for gadhafi, the reality for the u.s. is that the rebel leaders are now their only option. that said, lester, the rebel government has been torn by bickering among different factions and tribes. less than three weeks ago, their top military general was killed by some of their own fighters. it does raise questions about whether this transitional government can be trusted to create a broad-based government for the country.

some intelligence experts are warning tonight that there could be prolonged violence ahead. lester? >> andrea mitchell from our washington bureau, thank you. there is news tonight about the fate of two american men arrested by iranian authorities in 2009 along its border with iraq. the men said they were innocent hikers. but a court has now ruled otherwise, sentencing them to eight years in prison for spying. nbc's ali arouzi reports tonight from tehran. >> reporter: shane bauer and josh fattal each received eight years in prison for espionage and entering the country illegally. the two men and their friend, sarah shourd, were arrested a little over two years ago along the iran/iraq border. they denied they were spies saying they were hiking and crossed into iran by mistake. sarah shourd was released on bail last september. she flew back to the u.s. and never returned to iran to face trial. >> this could be the final -- >> reporter: she recently spoke with lester holt expressing hope

that her friends would soon be released. >> that's what we're praying for. we're praying the time for compassion has finally come. >> reporter: before today's sentencing, many thought bauer and fattal would be freed with time served and as a gesture of islamic compassion. now friends were concerned about the toll a long prison term would take. >> you are a pawn in a game that it's unclear what that game is. it has to be very tough. >> reporter: the case has highlighted differences among the ruling elite in iran. while the judiciary has taken a hard line, it was only two weeks ago that iran's foreign minister said he hoped bauer and fattal would be freed. today after the sentences were announced, the u.s. state department issued a statement saying -- we continue to express our hope that the iranian authorities will exercise the humanitarian option of releasing these two young men. observers believe the obama administration will continue its backdoor diplomacy to pressure tehran to free bauer and fattal. >> if that doesn't succeed, there's going to be an impetus to exact some kind of price on

the iranians for continuing to engage in this completely outrageous behavior. >> reporter: at this point, a humanitarian option may be the best hope for the two americans. it's the holy month of ramadan in iran, and traditionally, prisoners are pardoned at the end of it, which is ten days from now. lester, experts i've spoken to and conventional wisdom seem to suggest that bauer and fattal will be freed. having said that, the relationship between these two countries is that iran isn't in the business of doing the u.s. any favors. if they're not released in the next two weeks, they could be here for a long time. >> ali arouzi in tehran, thank you. it was an emotional day on a tiny island in norway where survivors of the massacre of 69 people at a youth camp returned to the scene to remember the friends and relatives they lost. we get our report tonight from nbc's jay gray. >> reporter: the boat ride may

have been just five minutes. but it was a difficult journey. >> i was scared and also filled with a little bit of anxiety. the images from last time were so horrible. >> reporter: these are the last images this young man and so many survivors had of utoya. >> we escaped our lives. everything was about getting away from it there. i was a bit scared and worried, yeah. >> caller: worried about what he would feel as he went back. a trip that he made on this ferry, the same boat that the confessed killer, anders breivik, used the day of the deadly attack. but as he coasted into the island where he spent the last ten summers, the sounds of screams and bullets gave way to a decade of what was so good about this place. >> it's ten years with good memories and one year with bad memories. but that was the result of one man. but the good memories from all those years is the results from hundreds and hundreds of good friends.

so they really live stronger in me now. >> reporter: the strength that took him back to the place he hid until the gunfire forced him into the water, the strength that helped him to leave personal memorials to friends who did not survive. a strength and comfort that only comes with being here and being together. none of those who escaped that horrific day will ever stand alone again. >> we are going to be veterans all our lives of this day that happened. we're going to be friends. we're going to know each other and we are hugging each other still. >> reporter: and holding tight to the memories 69 friends lost. jay gray, nbc news, just off utoya island. back in this country tonight, rescuers have found the body of a fourth victim after flash floods outside pittsburgh. seemingly out of nowhere, the streets there filled with water in some places up to nine feet,

washing away cars and in some cases, leaving people to swim for their lives. nbc's michelle franzen has the latest. >> reporter: swept away. flash floods killed four people outside pittsburgh, including a mother and her two daughters, who were trapped inside their submerged car. today search and rescue crews recovered the body of a fourth victim, an elderly woman who was reported missing. nearly a dozen others stranded in their vehicles say they barely had time to escape when water swallowed a section of road. >> i couldn't open my doors. i had to climb out through the window and sit on my roof. >> i called 911. they said, try to swim. but the water was over my head. >> reporter: amy says the low-lying stretch is known for flooding but has never seen anything like this. >> the road just exploded. water just started -- it was like geysers. >> reporter: rescue crews used boats to reach drivers like bob

bailey who appeared to be standing in waist-deep water. >> i was standing on my roof. and the water was up over like to my ankles. so it was covered. it was completely submerged in the water. >> reporter: emergency crews say back-to-back storms overwhelmed drain systems with water over nine feet deep. the water has since receded, leaving behind a string of vehicles and a layer of mud, the latest in extreme weather playing out. michelle franzen, nbc news, new york. tonight, president obama is wrapping up day three of a ten-day vacation trip to martha's vineyard with his family. and while the white house calls this a working vacation, the president's republican rivals are working the campaign trail targeting the president and the economy. nbc's mike viqueira has our report. >> reporter: rick perry was back on the campaign trail today in south carolina.

just seven days after joining the race, the conservative texan is now considered a top-tier candidate. >> getting america working again is the focus -- it's like a laser on our campaign. >> $16 trillion -- >> reporter: perry's rise has come in part at the expense of another surprise frontrunner, michele bachmann, who won the iowa straw poll also just a week ago. both perry and bachmann are competing for some of the same conservative tea party voters. but experts say that race to the right might end up helping president obama with key independent voters next year. >> to the extent the republicans playing up their differences and their positions, some of which are pretty conservative, that's good for the president. >> reporter: but the economy remains bad. three days into his august break on martha's vineyard, mr. obama used his weekly address to pledge more action and to slam congress. >> we need them to put aside their differences to get things done. >> reporter: since world war ii,

no president has been reelected with an unemployment rate of over 7.5%. that rate now stands at 9.1%. and experts predict it will be around 8% on election day 2012. >> we're looking at a economy for 2012 that at a minimum is going to feel recessionary and may actually be in a recession. >> reporter: with the weak economy a big target, republicans have not let up in their attacks on the president. >> the fact that this recession went on so long and has been so difficult from which to recover, a lot of the blame for that lies at the feet of the lack of presidential leadership. >> reporter: with campaign season now in full swing, republicans are in an all-out fight to take on a president who could be politically weakened by a struggling economy. mike viqueira, nbc news, washington. >> much more on decision 2012 on "meet the press" tomorrow morning. obama campaign adviser robert gibbs and indiana governor mitch daniels will be the exclusive guests. when "nightly news" continues on this saturday,

seasons change but the seemingly endless cycle of extreme weather does not. and later, he brings in the noise. meet the sound man for some of hollywood's biggest hits. is it a robot? no. is it a jet plane? nope. is it a dinosaur? [ laughs ] [ male announcer ] inside every box of heart healthy cheerios are those great tasting little o's made from carefully selected oats that can help lower cholesterol. stickers? uh-uh. a superhero? ♪ kinda. [ male announcer ] and we think that's the best prize of all. ♪ are switching from tylenol to advil. here's one story. i'm sean. i switched to advil 10 months ago. cyclists are a crazy bunch. when you're out there trying to push to your limits, you have some pain and it can be really vicious. i really like advil because it takes care of it all. neck, shoulder pain

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mark potter. >> reporter: from coast to coast, it's been a disastrous year weatherwise in the u.s. the worst was in joplin, missouri, which was demolished by a huge tornado in may with 160 people killed, 8,000 homes and businesses destroyed. during a rash of tornadoes this spring, many other cities were hit. >> in any year we typically see weather extremes. this year, however, we've seen the extreme of the extremes. >> reporter: in the southwest, extreme heat brought wildfires, drought, crop and livestock losses. flooding caused widespread damage in the upper midwest and mississippi valley. and early in the year, tons of heavy snow ground parts of the northeast and midwest to a halt. and now we're in hurricane season, where an above-average number of storms predicting. so far this year, only a weak tropical storm has hit the united states. but we are now entering the statistical height of hurricane season. the weather this year has killed

more than 600 people nationwide. and already nine separate weather events have each caused more than $1 billion in damage, tying a record set during all of 2008. total losses to homes, businesses and agriculture, $35 billion. forecasters blame the combination of an unusually active global weather pattern and population growth in vulnerable areas. >> even general weather nowadays has the potential to inflict more harm on society just because there are more people and there are more things in weather's way. >> reporter: to make america safer, the national weather service is launching a project called "weather ready nation." in six cities over the next month, it will test a new severe weather warning system and better emergency response procedures. >> we had over 540 people lose their lives in tornadoes alone this year. i know we can bring that number down. >> reporter: an effort to save lives in a year when the weather just will not let up.

mark potter, nbc news, miami. when we come back, predicting crime before it happens, the new high-tech way one city is protecting its streets. might turn into something more. and when it does men with erectile dysfunction can be more confident in their ability to be ready with cialis for daily use. cialis for daily use is a clinically proven low-dose tablet you take every day, so you can be ready anytime the moment's right. ♪ [ man ] tell your doctor about all your medical conditions and medications and ask if your heart is healthy enough for sexual activity. don't take cialis if you take nitrates for chest pain as this may cause an unsafe drop in blood pressure. [ man ] do not drink alcohol in excess with cialis. side effects may include headache, upset stomach, delayed backache or muscle ache. to avoid long-term injury seek immediate medical help for an erection lasting more than 4 hours. if you have any sudden decrease or loss in hearing or vision, stop taking cialis and call your doctor right away.

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automotive performance is gone. and all we have left are fallen leaves and broken dreams and -- oh. wait a second. that is a dodge durango. looks like american performance is doing just fine. ♪ carry on. ♪ we're back with a new tactic in law enforcement that sounds like it's straight out of a sci-fi flick, predicting where and when a crime might be committed. might remind you of the plot from the tom cruise thriller "minority report." but in one california city, it's real life. we get our report tonight from nbc's peter alexander. >> reporter: when santa cruz police received reports of a possible assault this week, sergeant christian lamoss was right around the corner. >> we can't be everywhere at once.

this was a neighborhood that was identified as a location that we needed extra patrols in. we came here, did extra patrols. >> reporter: stopped a crime. >> we were able to stop a crime in process. >> reporter: lamoss wasn't just there by chance. he was directed to that area by a computer program to uses up-to-the-minute data to find patterns and to predict where and when crimes might happen in the future. >> we liken this to earthquakes leading to aftershocks. just like the original crime, many crimes may follow it. >> reporter: it's called predictive policing. >> in this 500-by-500-foot area, crimes have been occurring that the model picked up on. >> reporter: this is a place you're going to revisit? >> we're going to revisit it today. >> reporter: before each shift, police officers are alerted to several hot spots, locations where they'll perform extra check. here in santa cruz, early indications suggest the program is working. in the first six months of this year, there were nearly a dozen burglaries or car thefts in this parking garage alone. last month, with the targeted patrols in place, there were

none. police arrested two women at that garage found casing cars. one for an outstanding felony warrant, the other for carrying illegal drugs. in fact, burglaries here were down 27% in july compared to the same month a year ago. nationwide, the city budgets being slashed and police forces dwindling, several cities and states are considering similar predictive policing programs including boston, chicago and los angeles. >> when times get tough, departments shrink in size. and we need to be more efficient in how we deploy our scarce resources. >> reporter: a new crime-fighting strategy where the motto for police isn't just to protect but to predict and serve. peter alexander, nbc news, santa cruz, california. seven months after she was shot in the head, we learned today that congresswoman gabi giffords now knows who was killed in that shooting rampage in tucson. her spokesperson says giffords

was deeply saddened by it. her inner circle had been keeping the names from her until they felt she was strong enough to handle the news. up next here tonight, behind the sound -- of movies. clinically proven to relieve tough pain twice as fast as before. what, did you invent this or something? well, my team did. i'm eric first, lead scientist at bayer. wow. look. it has microparticles. it enters the bloodstream faster and rushes relief right to the site of pain. better? great! thanks. [ male announcer ] new bayer advanced aspirin. extra strength pain relief. twice as fast. test our fast relief. love it, or get your money back. test our fast relief. do you often experience the feeling of a dry mouth? it can be the side effect of many medications. dry mouth can be frustrating... and ignoring it can lead to... sipping water can help, but dentists recommend biotene.

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[ male announcer ] glucerna. woman: day care can be so to save some money, i found one that uses robots instead of real people. 'cuz robots work for free. robot 1: good morning... robot 1: ...female child. sfx: modem dial-up noise woman: flaws? yeah, um, maybe. anncr: there's an easier way to save. anncr: get online. go to geico.com. get a quote. 15 minutes could save you 15% or more on car insurance. finally tonight, we want you to meet a guy who's making a lot of noise in hollywood. he's played key roles in some of the biggest movies of all time. though you haven't seen him on the big screen, you've no doubt heard him. here's nbc's amy robach.

>> reporter: in "the devil wears prada," anne hathaway is strolling. but it's not her heels you're hearing. no, they belong to this man, marco costanzo. and for him, nothing sachets like a 13 wide. >> 13 wide, very difficult to get. >> reporter: he's responsible for the sound effects of hundreds of hollywood movies. from heavy snow and broken glass to holsters and horses, he's making film magic with household items and in the most unlikely of settings. what could pass has a hoarder's basement is his state-of-the-art sound stage. a huge warehouse tucked away in new jersey and filled to the brim with just about anything from anywhere. >> i have no problem diving into a dumpster or lifting something off of a sidewalk that's being thrown away. new jersey has some of the best garbage in the world. >> reporter: and it's his trash that makes it to the big screen. remember the bath scene in "the big lebowski"?

jeff bridges is in the tub. but it's costanzo doing the splashing. he replicates every drop. in "true grit," whether it's a trot or a gallop, the best hooves often come from a tree. and for "good fellas," when it comes to all those hugs and back-slapping, forget about it. >> adding a sound to a film enables it to give it a sense of realism. if there was no sound, it would seem empty. but as soon as you bring in some of these other sounds, everything becomes a little bit more natural. >> reporter: natural but unexpected. take a haunted house or creaky door, for costanzo, the best sounds come from this butcher table, a gift from a friend. no matter the sound, he delivers.

and just remember the next time you see an actress walking in high heels, there's a chance he's the one you're hearing, every step of the way. amy robach, nbc news. that's "nbc nightly news" for this saturday. i'm lester holt reporting from new york. i'll see you tomorrow morning on "today" and right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com good evening, i'm diane dwyer. we begin with news from