The county's biggest storm total was 6.39 inches, at Picolata

The largest rainfall total the National Weather Service logged in St. Johns County during the nor’easter was 6.39 inches, at a mesonet station two miles north-northeast of Picolata. Of that, 5.51 inches fell between four o’clock and half past six on the afternoon of Oct. 5. As far as the official record goes that is the whole of the heavy rain here, and it is one afternoon on the St. Johns River side.

The weather service recorded four rainfall totals in this county. All four are dated Oct. 5.

The Picolata report says the rain fell in six hours. The Bakersville one says it started around half past one. By the evening the weather service had a flash flood report from five miles northwest of Bakersville, street flooding near Rivers Own Road, from a member of the public.

The next day it had one county flood report, at two in the afternoon: minor water over part of St. George Street, from a photograph posted to social media.

Then the flooding moved, and the gauges did not

The two reports that put this county on television came on Oct. 7, and both came from Palm Valley. At 8:45 that morning a weather service employee reported several inches or more of water covering portions of Wilderness Trail and Canal Boulevard. At 11:40 a broadcaster reported Roscoe Boulevard in Ponte Vedra completely covered, with water on the lawns as well.

Neither of those is a rainfall figure. The weather service logged no rainfall measurement anywhere in Palm Valley, on Oct. 7 or on any other day of the event, and it logged no rainfall measurement anywhere in St. Johns County after Oct. 5.

The nearest measured total to the flooded roads was taken in another county. A cooperative observer just north of Jacksonville Beach, about eight miles up the coast from the Palm Valley report, measured 5.90 inches, with the heaviest of it between half past seven and eleven on the morning of Oct. 6. A volunteer gauge a little further north had more than five inches the same day, and a mesonet station northwest of San Pablo had 5.71 inches in twenty-four hours. Picolata, which carries the county’s largest figure, is roughly twenty miles southwest of Canal Boulevard and on the other side of the peninsula. All four of them sit there.

So nobody measured the rain that flooded those two roads. The gauges are where they are.

What the county publishes about that road

The county does publish road drainage work by name. Its own site index carries a North Beach Drainage Study and a South Holmes Boulevard Drainage Improvements project, each on its own page.

A search of that index for Canal Boulevard returns nothing. Palm Valley drainage returns nothing either. A search for the single word Canal returns five pages, and not one of them is about a road.

That is not the same as saying no such record exists. It is what the county makes findable, and on this road that is nothing.

The county’s own advisory of Oct. 6 forecast an additional three to four inches of rain through Friday morning, and a forecast issued before the water arrived is a different kind of number from a gauge reading taken after it.

Two outlets covered the Palm Valley flooding. The only rainfall figure in either account is a resident’s estimate of more than ten inches, which no gauge in the weather service record supports or contradicts, because there is no gauge there.

What the numbers are, exactly

Every total above is preliminary. The weather service marks each report measured or estimated on its face. Picolata’s 6.39 inches, Bakersville’s 5.23 and the 4.30 at World Golf Village are all marked measured. The 4.50 inches at Pacetti Point is marked estimated, and the remark on the World Golf Village report says several stations in that area took over four inches, not one.

Three of the four county stations are mesonet sites or privately owned personal weather stations rather than instruments the weather service maintains itself, and the reports name each one so that a reader can see which is which rather than take a county total on trust. The one official gauge nearest the flooding is the cooperative observer at Jacksonville Beach, and it is in Duval County.