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Notes from "The Weather Machine: A Journey Inside the Forecast"

from Evan Hahn (dot com) [alt+shift+b] in technology

In The Weather Machine: A Journey Inside the Forecast, author Andrew Blum gives a high-level overview of global weather forecasting. What complexity hides behind the simple interfaces of our daily weather apps? Three main points stuck out to me: “The weather machine has to be a global system, and it won’t work any other way.” International collaboration is critical. Weather models need lots of global data to be effective. Weather technology, like the internet, is closely tied to military interests. Some quotes: “In a very practical sense, there were few clear distinctions between weather satellites and reconnaissance satellites, or cargo-carrying rockets and intercontinental ballistic missiles. It worked both ways. The military uses justified the meteorological efforts. The military efforts benefited the meteorological uses.” The NASA Jet Propulsion Laboratory “was haunted by the space program’s fundamental duality: They would create the machines that would open up a new era in human exploration—truly out to the edges of the solar system—while also creating the technologies that could destroy humanity.” “The only caveat written into the charter was that the World Weather Watch be used for peaceful purposes only.” Blum describes weather models as simulations, tweaked with real data. “Rather than a meat grinder that transmogrifies the weather of the present to the weather of the future (a one-way process), I now pictured two spinning earths side by side. I saw the real earth, the planet we live on, in the view we have gained from traveling to space. And I saw the model earth, its simulated atmosphere swirling with clouds and storms, with the bonus capability of being able to run in fast-forward, into the future.” The European Centre for Medium-Range Weather Forecasts is the “current and undisputed champion” weather model, according to this book. The book covered a wide range of topics and was fairly short, so it felt a little shallow. But it had been on my list for...
25th Jul 2025

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For example, all of these work even though they aren’t valid SQLite datatypes: -- SQLite doesn't support these types, but this is all accepted. CREATE TABLE tbl (name GARBAGE); CREATE TABLE tbl (name DATETIME); CREATE TABLE tbl (name JSON); CREATE TABLE tbl (name UUID); CREATE TABLE tbl (name BLOBB); I think these aren’t what the developer intended. Some of these are typos, some of them are misunderstandings of which datatypes SQLite supports, and some are egregious mistakes. Appending STRICT to any of these statements makes them error. In my opinion, that’s the correct behavior! -- All of these give errors, which I prefer. CREATE TABLE tbl (name GARBAGE) STRICT; CREATE TABLE tbl (name DATETIME) STRICT; CREATE TABLE tbl (name JSON) STRICT; CREATE TABLE tbl (name UUID) STRICT; CREATE TABLE tbl (name BLOBB) STRICT; Only INT, INTEGER, REAL, TEXT, BLOB, and ANY are allowed. Strict tables also require a column type, so you can’t do CREATE TABLE tbl (name). Still allows flexibility with ANY If you still need a column to be flexible, you can use the ANY datatype. As the name suggests, it allows anything—even in a strict table. CREATE TABLE tbl (value ANY) STRICT; -- All of these are valid because the column is ANY: INSERT INTO tbl (value) VALUES (123); INSERT INTO tbl (value) VALUES ('text'); INSERT INTO tbl (value) VALUES (12.34); INSERT INTO tbl (value) VALUES (X'8647'); I haven’t found a use for this, but maybe you will! Disadvantages of strict tables I prefer strict tables but I must share a few cons. Not everything is better! Can’t strict-ify an existing table I think it’s best to use strictness from the start, but that’s not always possible. Unfortunately, I don’t think there’s a way to ALTER a table to make it strict. I think you have to copy the data out of the non-strict table into the strict one. Something like this: -- 1. Create a new strict table with the same schema CREATE TABLE new_people (name TEXT) STRICT; -- 2. Copy data (risky if types are wrong!) INSERT INTO new_people SELECT * FROM people; -- 3. Replace the old table DROP TABLE people; ALTER TABLE new_people RENAME TO people; Note that this could be tricky if the non-strict table has invalid data! For example, if the old data accidentally contains text in an integer column, you’ll get errors when doing the migration. You’ll probably need to clean the data or cast it. You could make a rule for your codebase that all new tables are strict. That might be useful—at least some of your tables are valid! But it might also mean you have inconsistent validation across your tables, which might be more surprising than having weak validation on all tables. It’s up to you to decide whether this is a good fit for you. The SQLite developers disagree with me SQLite has a whole page called “The Advantages Of Flexible Typing”, where they argue that SQLite’s flexible behavior is good, actually. I hesitate to wade into the controversy of static-versus-dynamic, but I disagree in most cases. I’ve personally encountered many bugs where an unexpected data type caused subtle headaches. I’d much rather these mistakes explode loudly. But it’s worth noting that SQLite’s developers seem not to share my preference for strict tables! They point out a few good uses for flexible tables, such as “a pure key-value store” or “a place to store miscellaneous attributes” of different types. They also mention that you might want to keep the invalid data in some cases, like if you’re directly importing a messy CSV and don’t want to lose any data. I still prefer strict tables, but acknowledge there are some reasonable cases for non-strict ones. (There’s also at least one comment in the SQLite source that calls non-strict tables “legacy”, but I trust that less than the official documentation.) Only in SQLite 3.37.0+ SQLite introduced strict tables in version 3.37.0, released November 2021. 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