Believe it or not I was taught this sort of thing in the Army.
No, you will not survive if you’re at work. The blast would vaporize your building at that close a range.
There is a chance you will survive the initial blast if you are at home. However, that’s a chancy thing. Anyone unfortunate enough to be outside who has a clear line of sight to the explosion will likely be burned to death by the flash; if they are looking towards the WTC site at the time, they’ll probably be blinded as well. A one-megaton bomb will set fire to almost anything combusible at six miles on a clear day. The range of a bomb set off at ground level won’t be as far as if it were exploded in the air, but six miles is close for a 1-megaton bomb (even by superpower standards that’s a huge bomb.) Your house will probably be set on fire by the thermal flash, and if exposed your car will probably be destroyed as well, set on fire and the tires melted. If you’re inside at the time there you could likely escape your burning house, but your car will be burning like a campfire.
One cannot overemphasize the importance of NOT LOOKING AT IT. Even after the initial flash, the fireball will be blindingly bright for several moments afterwards, enough to blind you and cause third degree burns. It is absolutely essential that you be shielded from the thermal flash during and immediately after the explosion.
Remember also the danger of having almost everything on fire; gas mains can explode, fuel tanks rupture, gasoline-fuelled vehicles can blow up.
Even if your car is spared - if it’s behind your house relative to the WTC, say - it’s possible the electromagnetic pulse will render it useless anyway. Unless it’s a really old car.
- Following the thermal flash will come a shockwave that, at 6 miles, will probably knock your house down. Again, the shockwave is weaker than it would be if the bomb were airburst, so if there is a lot between you and the WTC site, your house may be spared. However, the devastation at 6 miles will be huge; most buildings will be destroyed. A 1-megaton bomb will knock over most structured at 10 miles.
The shockwave will be followed by tremendous, hurricane force winds, extraordinarily hot and very powerful. At 6 miles it could be enough to kill you if the heat and shockwave haven’t already.
You would also have substantial seismic damage as well.
In general, I would say that at six miles your odds of survival are not good if a bomb that powerful were set off. At six miles you will be subjected to thermal effects and a shockwave so powerful that escape would be extremely difficult.
However, it is unlikely a terrorist bomb would be so large. 1 megaton is larger than most nuclear weapons. You would probably be looking at a detonation of 10-200 kilotons (a 200 KT bomb is still a friggin’ big bomb) and in that case your odds of survival are actually pretty good at 6 miles.
It’s difficult to say how quickly you’ll be poisoned by radiation, since it depends on how the weather is. That won’t kill you instantly with a smaller bomb, so you may as well PUFO as quickly as you possibly can.
Stay low, in the basement if possible, until the blast effects of the bomb - thermal flash, shockwave, and wind - are passed.
Then, assuming you don’t have a fallout shelter built into your home, get away from the explosion as quickly as possible.
It is possible that you may have family members needing immediate medical attention. However, the number of people injured in a Manhattan nuclear blast would exceed the available medical services of the entire State of New York, so you should be prepared to render medical aid on your own. Even for a small bomb, anyone unfortunate enough to have a line of sight to the burst will be burned. Have first aid supplies close at hand. Antibiotics and disinfecting agents are critical for treating bad burns.
Have a contingency plan in case your car is rendered useless by EMP. Strollers, baby carriages, bicycles can all be used to transport kids and supplies. Naturally, your leaving may be directed by federal of Guard troops or other government agents. Follow their instructions if they seem to know what they’re doing; avoiding panic and cooperating will be key to keeping things going as smoothly as possible.
It won’t be hard to see where the fallout is headed; the mushroom cloud will visibly move with the wind. So you can adjust your direction of flight accordingly. It also would not hurt to wear surgical masks or some other form of protection, and maybe raincoats or ponchos, and gloves. If you can avoid breathing in irradiated particles and keep it off your skin, you can minimize your risk as much as might be possible.
At your distance, I would think it is QUITE probable that you and your family can survive a nuclear blast of the sort a terrorist would set off. Just keep a level head.