As a preface, let us clearly understand the evolving situation...
In military parlance, Israel is what is termed a 'one bomb country'. What this means in essence is that 'one nuke' detonated over Tel'Aviv would constitute a catastrophic and fatal strike on Israel. One out of every six Israelis live in Tel'Aviv, and it is the financial and communications hub of the nation.
The Iranian nuclear program is immense, and 300 facilities are expressly dedicated to nuclear research and development. Taking a cue from North Korea, many Iranian nuclear facilities are located either underground or within mountains. The scattered surface facilities are all ensconced within concentric rings of anti-air-missile batteries. Iranian scientists, engineers, and technicians well understand the 'nuclear fuel cycle'. What they lack is practical hands-on experience in managing all facets of nuclear technology. Even so, they have now arrived at a critical juncture in nuclear weapons develpoment known as the cascade-centrifuge. There is only one use for this technology and that is to obtain enriched weapons-grade uranium from uranium-hexaflouride, which is a by-product of the nuclear fuel cycle. A one thousand unit cascade will yield enough weapons-grade uranium to produce from one to five nuclear weapons per year.
It has been proposed by many that Israel should launch a conventional and preemptive air strike against Iran. To be quite frank, this is not a viable possibiity for numerous reasons. Geographical distance and a large target universe are the main negative considerstions. Israeli fighter jets would have to refuel somewhere enroute to accomplish a round-trip strike. The rich target universe would demand hundreds of sorties over the course of many days. In the interrum, Iran would certainly launch conventional missiles against Israel... with possible C&B warheads. In summation, the only country with the requisite military resources to launch a comprehensive and lengthy preemptive strike against Iran is the United States.
Despite the numerous carrot and stick negotiations conducted by many nations and organizations to curtail Iranian nuclear proliferation, Iran seems determined to possess nuclear warheads. In the not too distant future, Iran will arrive at what Israel has termed the 'tipping point'. This is a precise point where Israel will be able to determine with certainty that Iran is nuclear weapons capable.
This thread is entitled 'Israeli nuclear counterstrike'. Unlike the president of Iran, Israel has never threatened any nation with nuclear armageddon. Thus the thread author assumes that Israel will self-limit itself to retaliatory nuclear strikes against Iran. I reiterate... Israel is a one-bomb country. Ponder that truism and then reconsider the thread premise. Could it be flawed? Must Israel wait until its very heart is lanced with a mortal wound? Would you?