The phrase "alarmingly slow" is correct and usable in written English.
It can be used to describe something that is surprisingly or worryingly slow, often in a negative context.
Example: "The internet connection was alarmingly slow, making it difficult to complete my work on time."
Alternatives: "worryingly slow" or "concerningly slow".
A year into recovery, job growth has been halting and alarmingly slow.
Before "Breaking Bad" came to town, its owner, Tami Abts, ran a one-woman shop, but by the end of filming for the fifth season, her staff had ballooned to 10. Business was alarmingly slow through the spring and summer — and she scaled down to one employee — though last week it began to pick up again, she says.
We are alarmingly slow in building a homeland defense that can win Americans' confidence.
On Feb. 23, he collapsed at his Port St . Luciehome with difficulty breathing and an alarmingly slow heart rate.
CHINA has been alarmingly slow in coming to terms with the potential scope of the Year 2000 problem: the danger that some computers and computer software may fail because of an inability to realise that a year which ends with the digits "00" may come after one ending in "99".
Molecular mechanism of hepatic fibrosis has been elucidated much more clearly, however, progress in the treatment of liver fibrosis remains alarmingly slow [ 5, 6].
A week after the mother's due date, I learned, the fetus's heart rate had slowed alarmingly and he was delivered by emergency Caesarean section.
China's growth rate will slow somewhat in 2012, but not alarmingly: its economy will expand by 8% or so, faster than all but a dozen countries.
U.S. auto sales could slow over the next few years, but not alarmingly, a dealer group said in its latest forecast.
China's economy, once the fastest growing in the world, has slowed down alarmingly fast.
But the papers did not report the fine type, so to speak, which showed that almost all the recent gain was made by families with incomes of over $7,500, and that the rate at which poverty is being eliminated has slowed down alarmingly since 1953.
