From 9c15f093a1705b52807d44ab02a57f40249ee977 Mon Sep 17 00:00:00 2001
From: Bilawal Sidhu <bilawal@halfpixel.ai>
Date: Wed, 23 Sep 2026 21:54:43 -0500
Subject: [PATCH] fix(cyclones): accept advisories NHC publishes before their
 nominal time

NHC stamps an advisory with its nominal time and writes it about half an
hour early, so the 5-minute future limit rejected the whole feed each
advisory cycle and the layer showed no storms. Allow 90 minutes ahead.
---
 CHANGELOG.md                    | 5 +++++
 server/providers/cyclones.js    | 5 ++++-
 src/data/cyclonesProxy.test.mjs | 9 +++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 58103d04d..431d282f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+- Cyclone advisories no longer go dark while NHC publishes an advisory ahead
+  of its nominal time: advisory and position times up to 90 minutes ahead of
+  the server clock are accepted (previously 5 minutes), so the whole feed is
+  not rejected for about half an hour each advisory cycle.
+
 - Public Overpass instances are no longer used by default. Street Traffic
   roads come from TomTom flow tiles, OpenFreeMap vector tiles, or both, chosen
   on the layer row (TomTom / OSM / Hybrid) or with `?trafficRoads=`. With a
diff --git a/server/providers/cyclones.js b/server/providers/cyclones.js
index fede1aade..d580357ce 100644
--- a/server/providers/cyclones.js
+++ b/server/providers/cyclones.js
@@ -41,6 +41,9 @@ function number(value, min, max) {
   const n = Number(value);
   return Number.isFinite(n) && n >= min && n <= max ? n : null;
 }
+// NHC stamps an advisory with its nominal time (e.g. 03:00Z) and publishes it
+// up to about half an hour before; allow that, but not a clock far ahead.
+const EARLY_ADVISORY_MS = 90 * 60_000;
 function iso(value, now) {
   if (
     typeof value !== 'string' ||
@@ -50,7 +53,7 @@ function iso(value, now) {
   const n = Date.parse(value);
   if (
     !Number.isFinite(n) ||
-    n > now + 5 * 60_000 ||
+    n > now + EARLY_ADVISORY_MS ||
     now - n > 12 * HOUR ||
     new Date(n).toISOString().replace('.000Z', 'Z') !==
       value.replace('.000Z', 'Z')
diff --git a/src/data/cyclonesProxy.test.mjs b/src/data/cyclonesProxy.test.mjs
index 04729d33a..31433b326 100644
--- a/src/data/cyclonesProxy.test.mjs
+++ b/src/data/cyclonesProxy.test.mjs
@@ -162,6 +162,15 @@ test('malformed, duplicate, oversized, future and expired status is rejected rat
   assert.deepEqual(parseCycloneStatus({ activeStorms: [] }, NOW), []);
 });
 
+test('advisories published before their nominal time are accepted, far-future ones are not', () => {
+  // NHC wrote the 03:00Z advisory at 02:34Z.
+  const early = Date.UTC(2026, 8, 16, 2, 34);
+  assert.equal(parseCycloneStatus(status(), early)[0].issuedAt, TIME);
+  assert.throws(() =>
+    parseCycloneStatus(status(), Date.UTC(2026, 8, 16, 1, 25)),
+  );
+});
+
 test('coherent geometry is retained with holes/dateline while older advisory geometry is omitted', () => {
   const storms = parseCycloneStatus(status(), NOW);
   const parts = collections();