If the U.S. Federal Reserve's plans are changing week to week, then the concept of "forward guidance" as a policy tool has been well and truly abandoned.

The latest of this year's financial market quakes is a snapshot of how one of the three main monetary policy levers has been junked of necessity and, probably, by choice.

Just three months ago on March 4, Fed chief Jerome Powell told reporters that an outsize interest rate rise of 75 basis points was not something the central banks' policy committee was "actively considering" as part of its planned series of rate hikes to rein in 40-year high U.S. inflation.

While interest rate and bond markets were jolted somewhat by May inflation numbers released on June 10, Fed officials were in their traditional period of premeeting silence.

But all hell broke loose when the Wall Street Journal's Fed watcher Nick Timiraos on Monday reported the Fed would in fact "consider" a 75-point move.

The entire fixed income complex heaved and was forced to reprice an entirely new and elevated Fed trajectory from last week out to a peak of some 4% peak rates by March of next year. Stock markets nosedived worldwide and the dollar surged.

The last minute guessing game and jumpy decisionmaking — assuming the Fed was involved at all — is a stark departure from years of "forward guidance" designed not to shock markets, enhance transparency and allow investors months or years to absorb changes in policy tack.

The implication for investors is that Fed deliberations and those of other central banks will become far less predictable over the coming months and possibly years — implying greater uncertainty and volatility are on the horizon and will require higher risk premiums to compensate.

Pictet Wealth Management's Thomas Costerg reckons the Fed's reaction function has becoming "backward looking," panicked about past high inflation and prone to political pressure.

Pimco economist Allison Boxer feels the Fed will keep hiking beyond September — creating a "serious risk of overtightening."

But "forward guidance" long into the future has been heavily criticized by many economists.

Should the central bank guide clearly on long rates but not policy shifts?

With an unwind in the Fed's balance sheet also now in the mix, the Fed may see some trade-off between the two to manage a very bumpy ride ahead.

Dolan is editor-at-large for finance and markets at Reuters.