NephosArtworks & their sources
John Constable, Cloud Study, Yale Center for British Art, B1981.25.116
John Constable. Yale Center for British Art, Paul Mellon Collection. Public domain / CC0. Catalogue

Object research · John Constable

Cloud Study

Yale Center for British Art
B1981.25.116

How far do independent weather sources support Constable’s account?

Current finding · Nephos analysis

The regional wind sources are compatible with an easterly flow, but neither measured Constable’s assumed site. The computed Sun is consistent with early afternoon, yet the horizonless picture cannot test the stated time or southward view. The day lay in a mild spell, but its daily mean was slightly below the long-run calendar-date average, so “warm” remains open.

01 / Read the wording

Similar words.
Different kinds of evidence.

A comparison of language, not an automatic translation into weather measurements.

TermArtist’s accountOther sourceWhat follows · Nephos
Wind
“wind very fresh at East”
Catalogue transcription
“NE” · Howard’s register, 21 September 1822. London area; exact station attribution and observation hour are not labelled on the table. Historical documentEast and northeast are neighbouring sectors. Strength words have no shared numerical scale; this is partial agreement, not identical observation.
Warmth
“but warm”
Catalogue transcription
No equivalent quoted warmth description is established here. Regional temperature context is separately described below.A felt quality cannot be converted into a temperature threshold. A regional daily composite or model estimate cannot establish how warm the artist felt.
Direction
“looking south.”
Catalogue transcription
No independent viewing direction is recorded in the weather table.The artist’s view direction differs from the direction the wind comes from. No horizon or landmark establishes the painted bearing.
Cloud

Nephos reading: no cloud-type term occurs in this inscription.

Catalogue transcription
“Fine.” · Howard’s note covering 17–21 September. Historical document“Fine” is a period description, not a cloud fraction or a classification of the painted forms.

DescribedWords used by a person in a particular context.

MeasuredInstrumental records, with their own location and time coverage.

EstimatedModel outputs or derived calculations, with assumptions and uncertainty.

02 / Making the artwork

The sky passed through
an artist’s decisions.

Production uncertainty is separate from weather-model uncertainty. The located sources do not establish every stage of this object’s making.

Location · partly known
Hampstead is a series-level attribution; the exact easel coordinates are an analytical assumption. Catalogue basis Affects view direction and solar comparisons.
Date evidence
Securely dated inscription. The date is carried through a museum catalogue transcription, not an independently timed observation of execution. Source · Affected claim
Outdoor execution · unresolved
The evidence assembled here does not establish that every passage was executed outdoors in the stated interval. Affects whether the inscription claims can be tested against depicted light or cloud forms.
Preparatory work & later changes · unknown
The retained analysis includes an x-radiograph discussion, but it does not establish a complete sequence or timing of working sessions. Analysis receipt No preparatory-sketch sequence is established here. Unknown is not evidence that there were none. Affects any inference from painted form to a momentary sky.
02 / Atmosphere

Four witnesses,
none of them the painting.

The verified capture analysis is retained, while the catalogue correction resets the time to 13:30. Each comparison names its scale and its limit.

Image-derived measurements below refer only to capture ycba_627_recto_cropped. They describe this museum photograph, not an independent atmospheric observation. Retained analysis receipt.

Y2 · Solar geometry

The afternoon sun

At the inscribed time, treated as 13:30 local mean time, the sun stood 35.3° above the horizon at azimuth 210.3°. The stored 13:00 and 14:00 samples form a one-hour sensitivity band around that primary point, from 37.3° to 32.6° altitude and 201° to 219° azimuth. Y2

A pure sky with no horizon yields no measurable painted solar direction, so no painted-versus-computed angular residual is reported.
E · 90° S · 180° W · 270° 13:30 · 35.3°
Assumed site: Hampstead, 51.56° N, 0.165° W. Skyfield 1.55, JPL DE440; local mean time.
Y4 · Regional reconstruction

A weather record with no eyes

At 13:00 over the 1° grid cell nearest London, the 20th Century Reanalysis reconstructs a wind from ENE, 57°, at roughly 5.9 m/s. Constable wrote “wind very fresh at East.” Y2

It places cloud cover near 61%, with ±33 percentage points of ensemble spread; the capture-specific segmentation measured 58% opaque cloud. The estimates are compatible within wide uncertainty, not a match. Y2

This is regional context, not an observation at the assumed Hampstead site. At London’s latitude, the grid cell is about 111 × 68 km, and its cloud-cover spread is comparable to its mean.
57°wind from ENE
5.9metres per second
61 ± 33percent cloud cover
Y5 · Thermometers

“But warm”

The reanalysis gives 14°C at the nearest stored hour. The Central England Temperature series records a daily mean of 11.6°C on 21 September. The day sat inside a mild spell that fell to 9.5°C by the 26th, yet 11.6°C was slightly below the prior 50-year average for that calendar date, about 12.6°C. Y2 Y5

Neither source defines “warm,” and neither measures conditions at Constable’s position. Central England Temperature is a regional daily composite.
14°Creanalysis, target hour
11.6°CCentral England daily mean
9.5°Cdaily mean, 26 September
Y6 · Luke Howard

The written register

Luke Howard’s London-area table records NE for 21 September and labels the 17th through the 21st “Fine.” Constable wrote East for the assumed Hampstead site. Y6

East and northeast are adjacent compass sectors, not identical readings. Across different London locations, this is near-agreement rather than a match.

The day-21 cell and notes line were checked directly against the scanned page image. Station attribution is not labelled on the table page.
NEHoward, 21 September
“Fine.”note for 17–21 September
9 of 30September days logged NE
03 / Evidence

The verdict,
claim by claim.

“Sep[br] 21. 1822.”

Unknown

A second inscription by Constable gives the same date. This is internal consistency between two notes from the same hand, not confirmation from a separate observer. Y7

“½ p’s[t] one o clock.”

Unknown

The computed Sun at 13:30 is consistent with early afternoon, but a horizonless pure sky supplies nothing against which to test the stated time. Y2

“looking south.”

Unknown

Consistent, but untested. He painted no horizon and no landmark, so there is nothing to measure a bearing against. Nephos leaves this one open rather than invent a number. Y2

“wind very fresh at East,”

Partially agrees

For the assumed Hampstead site, Constable wrote East; Howard’s 21 September cell reads NE at his station. They are adjacent sectors, not identical readings. The reanalysis reconstructs ENE between them; strength is compatible only at grid scale. Y2 Y6

“but warm.”

Unknown

The day sat inside a mild spell that fell sharply by the 26th, yet its 11.6°C daily mean was slightly below the prior 50-year average for 21 September, about 12.6°C. No source defines “warm,” and none measures Constable’s position. Y2 Y5

What this record will not say: that a weather cell about 111 × 68 km speaks for the assumed Hampstead site, that 33 points of uncertainty round down to certainty, or that consistent values confirm subjective words. The limits live beside the findings.

04 / Bottom line

What a visitor can take away.

The regional wind sources are compatible with an easterly flow, but neither measured Constable’s assumed site. The computed Sun is consistent with early afternoon, yet the horizonless picture cannot test the stated time or southward view. The day lay in a mild spell, but its daily mean was slightly below the long-run calendar-date average, so “warm” remains open.

03 / Interpretation history

How the reading changed.

18 August 2026 · transcription verification

Yale howard retranscription

Original claim
Howard's day-21 wind appeared compatible with Constable's inscribed East, but Nephos's first NE reading came from OCR row-counting and was explicitly marked for a page-image check before archival citation.
Conflicting evidence / limits
The first NE reading came from OCR row-counting and was explicitly unready for archival citation. Direct inspection on 18 August 2026 established that Howard's cell reads NE, not E; it is also from a different London location than the assumed Hampstead site.
Current conclusion · Partially agrees
Direct inspection established the transcription, while source distance and the non-identical directions kept the comparison at partial agreement.
Supporting sources & retained versions

Recorded in the 2 September 2026 discrepancy packet · exact change date not retained

Yale cloud amount comparison

Original claim
The Yale capture segmentation measured 58% opaque cloud while the 20th Century Reanalysis ensemble mean was 61% cloud, with ±33 percentage points of ensemble spread, over the London-area grid cell.
Conflicting evidence / limits
The 61% ensemble mean carries +/-33 percentage points of spread over a regional 1-degree grid cell, while 58% is a capture-specific paint segmentation rather than an atmospheric observation.
Current conclusion · Partially agrees
The three-point proximity is presented only as compatibility within wide uncertainty.
Supporting sources & retained versions

7 September 2026 · presentation revision

A research companion around the existing evidence.

Findings moved forward; source-language comparisons and production limits made explicit. No new weather observation or independent validation was added. Read the preserved pre-rework page. The archive label identifies this predecessor snapshot; its original edit time was not recorded.

04 / Take this into your work

A record you can refer to.

Discuss using this record ↗

Version 2026-09-07. Cite individual claims by their link; cite museum and historical sources directly when using their statements. Nephos analysis is independent of the holding institution. Image licences are separate from the research text.