From c7f9aac3f948bbe141a36d14e1dd47b8f638b990 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Thu, 16 Apr 2026 09:45:21 -0500
Subject: [PATCH] NarrClient: parse cdo numeric codes for cdo-version
 independence
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Prod cdo 2.5.1 (Debian) emits named shortnames (tpag10, 2tag2, saip, code11…)
where cdo 2.6.0 (Mac) emits var11/var33/etc. The parser only recognized
varNN, so every prod NARR fetch failed with "no parseable values in cdo
output" and all 350 in-flight jobs discarded.

Switch cdo args from `-outputtab,name,lev,value` to `-outputtab,code,...`.
cdo then outputs the raw numeric NCEP GRIB1 parameter code regardless of
version, and @cdo_code_to_name maps that integer to the semantic name we
already use downstream (TMP/HGT/SPFH/…).

Verified by reproducing on both a 2010 NARR file (fixture) and a 2007 file
fetched live — both now emit identical numeric code rows.
---
 lib/microwaveprop/weather/narr_client.ex | 40 +++++++++++++-----------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/lib/microwaveprop/weather/narr_client.ex b/lib/microwaveprop/weather/narr_client.ex
index a170c8e9..5622aab8 100644
--- a/lib/microwaveprop/weather/narr_client.ex
+++ b/lib/microwaveprop/weather/narr_client.ex
@@ -38,19 +38,21 @@ defmodule Microwaveprop.Weather.NarrClient do
     {"PWAT", "atmos col"}
   ]
 
-  # cdo emits NCEP GRIB1 parameters as `varNNN`. This table maps the cdo
-  # parameter token to the semantic NCEP short name, verified empirically
-  # in the spike (see plan doc cdo lookup table).
-  @cdo_var_to_name %{
-    "var1" => "PRES",
-    "var7" => "HGT",
-    "var11" => "TMP",
-    "var17" => "DPT",
-    "var33" => "UGRD",
-    "var34" => "VGRD",
-    "var51" => "SPFH",
-    "var54" => "PWAT",
-    "var221" => "HPBL"
+  # Map NCEP GRIB1 parameter codes to our semantic short names.
+  # Using `-outputtab,code,...` (instead of `name`) makes cdo emit the raw
+  # numeric param code, so the same parser works across cdo versions that
+  # would otherwise produce either `varNN` (Mac / cdo 2.6) or `codeNN` +
+  # named shortnames like `tpag10` / `2tag2` / `saip` (Debian / cdo 2.5.1).
+  @cdo_code_to_name %{
+    1 => "PRES",
+    7 => "HGT",
+    11 => "TMP",
+    17 => "DPT",
+    33 => "UGRD",
+    34 => "VGRD",
+    51 => "SPFH",
+    54 => "PWAT",
+    221 => "HPBL"
   }
 
   @doc """
@@ -289,7 +291,7 @@ defmodule Microwaveprop.Weather.NarrClient do
 
   defp run_cdo_outputtab(grb_path, lat, lon) do
     args = [
-      "-outputtab,name,lev,value",
+      "-outputtab,code,lev,value",
       "-remapnn,lon=#{lon}_lat=#{lat}",
       grb_path
     ]
@@ -307,8 +309,6 @@ defmodule Microwaveprop.Weather.NarrClient do
     raw =
       stdout
       |> String.split("\n", trim: true)
-      |> Enum.map(&String.trim/1)
-      |> Enum.filter(&String.starts_with?(&1, "var"))
       |> Enum.reduce(%{}, &accumulate_cdo_row/2)
 
     if raw == %{} do
@@ -329,9 +329,13 @@ defmodule Microwaveprop.Weather.NarrClient do
     end
   end
 
+  # Rows are three whitespace-separated numeric columns: <code> <lev> <value>.
+  # Header, cdi warnings, and cdo progress lines lack the three-number shape
+  # and fall through to :error.
   defp parse_cdo_row(line) do
-    with [var_token, lev_str, value_str] <- String.split(line, ~r/\s+/, trim: true),
-         {:ok, name} <- Map.fetch(@cdo_var_to_name, var_token),
+    with [code_str, lev_str, value_str] <- String.split(line, ~r/\s+/, trim: true),
+         {code_int, ""} <- Integer.parse(code_str),
+         {:ok, name} <- Map.fetch(@cdo_code_to_name, code_int),
          {lev_int, ""} <- Integer.parse(lev_str),
          {value_float, ""} <- Float.parse(value_str) do
       {{name, lev_int}, value_float}