From ebae24b38ecd65f5c07f8b6f063c091212ecab5d Mon Sep 17 00:00:00 2001
From: XANTRONIX Industrial <xan@xantronix.com>
Date: Sat, 8 Mar 2025 22:39:41 -0500
Subject: [PATCH] Implement finding equilibrium level

Other changes:

* Rework Series.intersect() to return a tuple containing temperature,
  pressure

* Rework other methods returning Series to return a tuple containing
  temperature, pressure
---
 lib/xmet/series.py   |  4 ++--
 lib/xmet/sounding.py | 21 ++++++++++++++++++---
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/lib/xmet/series.py b/lib/xmet/series.py
index d7b15d2..2835594 100644
--- a/lib/xmet/series.py
+++ b/lib/xmet/series.py
@@ -7,7 +7,7 @@ class Series(dict):
     def __init__(self):
         super().__init__()
 
-    def intersect(self, series: Self):
+    def intersect(self, series: Self) -> tuple[float]:
         pairs = nearest(sorted(self.keys(),   reverse=True),
                         sorted(series.keys(), reverse=True))
 
@@ -19,6 +19,6 @@ class Series(dict):
             sign = cmp(v1, v2)
 
             if sign == 0 or (sign_last is not None and sign_last != sign):
-                return pair[0]
+                return v1, pair[0]
 
             sign_last = sign
diff --git a/lib/xmet/sounding.py b/lib/xmet/sounding.py
index 44fdb7f..22d373f 100644
--- a/lib/xmet/sounding.py
+++ b/lib/xmet/sounding.py
@@ -185,7 +185,7 @@ class Sounding(DatabaseTable):
 
         return series
 
-    def find_lfc(self, temp: float, pressure: float) -> float:
+    def find_lfc(self, temp: float, pressure: float) -> tuple[float]:
         moist_adiabat = follow_moist_adiabat(temp, pressure)
         temp_line     = self.follow_temp()
 
@@ -196,7 +196,20 @@ class Sounding(DatabaseTable):
             v1, v2 = moist_adiabat[pair[0]], temp_line[pair[1]]
 
             if v1 > v2:
-                return pair[0]
+                return v1, pair[0]
+
+    def find_el(self, temp: float, pressure: float) -> tuple[float]:
+        moist_adiabat = follow_moist_adiabat(temp, pressure)
+        temp_line     = self.follow_temp()
+
+        pairs = nearest(sorted(moist_adiabat.keys(), reverse=True),
+                        sorted(temp_line.keys(),     reverse=True))
+
+        for pair in pairs:
+            v1, v2 = moist_adiabat[pair[0]], temp_line[pair[1]]
+
+            if v1 < v2:
+                return v1, pair[0]
 
     def derive_parameters(self) -> SoundingParameters:
         dry_adiabat = follow_dry_adiabat(self.samples[0].temp,
@@ -206,10 +219,12 @@ class Sounding(DatabaseTable):
                                                           self.samples[0].pressure)
 
         lcl = dry_adiabat.intersect(saturated_mr_line)
-        lfc = self.find_lfc(dry_adiabat[lcl], lcl)
+        lfc = self.find_lfc(lcl[0], lcl[1])
+        el  = self.find_el(lfc[0], lfc[1])
 
         params = SoundingParameters()
         params.lcl = lcl
         params.lfc = lfc
+        params.el  = el
 
         return params