(John Kemp is a Reuters market analyst. The views expressed are his own)

LONDON, April 8 (Reuters) - U.S. crude production will peak this month, according to revised forecasts published by the country’s Energy Information Administration (EIA).

Output will average 9.37 million barrels per day (bpd) in April and the same in May before falling to 9.33 million bpd in June and 9.04 million bpd by September, the EIA predicted in the April edition of its Short-Term Energy Outlook (STEO).

Production is expected to peak a month earlier and 10,000 bpd lower than the EIA forecast in the January STEO, reflecting continued low wellhead prices and a sharper-than-expected slowdown in new well drilling.

Production is forecast not to exceed this month's level for another 18 months. The EIA has cut its forecast for the end of 2016 by 230,000 bpd compared with three months ago (link.reuters.com/ped54w).

While the EIA’s Brent price forecast is largely unchanged, prices for West Texas Intermediate crude have been marked down through the rest of 2015 and 2016, reflecting the build-up of crude stocks and persistent weakness of U.S. grades.

The number of rigs drilling for oil has fallen further and faster than was anticipated last year. Baker Hughes reported there were 802 rigs drilling for oil last week, down exactly 50 percent since early October.

It is unlikely a halving of the rig count can be completely offset by greater target selectivity and other efficiency improvements such as employing only the most powerful rigs, drilling longer laterals and reaching target depth faster.

Drilling data points to a strong probability that production from new wells will soon start to fall - if it is not falling already. Given the rapid declines in output from wells drilled in 2013 and 2014, total output from new and legacy wells should start to fall soon.

DATA DELAYS

The most common question I am asked at the moment is: if the rig count has fallen by 50 percent, why is output still rising?

The simple answer: there is a delay of six months or more between changes in the number of new wells being drilled and reported changes in production.

It can take 20-30 days for a rig to drill a new well and then another 60 days or more for the well to be fractured and all the above-ground equipment put in place before the well flows its first oil.

Most major oil-producing states require well operators to submit a monthly report on the amount of oil and gas produced, but the first report is not usually due for up to two or three months after a new well has begun flowing.

Even then, the first report may not be representative of a full month’s production because the well may have started flowing part way through the month in question.

Once production reports are submitted they have to be compiled and published by state regulators, adding a further delay.

Then there are late filings (“delinquent wells”) from operators submitting after the formal legal deadline has passed, which means the initial production totals can be revised, sometimes substantially, especially in Texas where there are lots of small owners and operators.

The EIA includes estimates for U.S. production in its weekly and monthly publications. However, these are based on extrapolating from limited data and subject to estimating errors, which are likely to be especially large when the production trend is changing.

Rig counts are a leading indicator of future production trends (albeit a very imperfect one), while production reports are a lagging indicator.

Trying to predict future production based on current production reports is like attempting to drive by looking in the rear-view mirror.

Even if production peaks this month or next, it will not be visible in the statistics until at least July or August, and maybe later.

But by the time the production peak becomes visible, output will likely have been falling for several months. (Editing by Dale Hudson)