Update to most_unstable_cape_cin to include the LCL in the profile

if the start of the most unstable parcel is below the LCL. Closes #1108.
Unidata · Jul 23, 2019 · 4934b52 · 4934b52
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commit 4934b52
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diff --git a/metpy/calc/tests/test_thermo.py b/metpy/calc/tests/test_thermo.py
@@ -960,7 +960,7 @@ def test_most_unstable_cape_cin_surface():
     dewpoint = np.array([19., -11.2, -10.8, -10.4, -10., -53.2]) * units.celsius
     mucape, mucin = most_unstable_cape_cin(pressure, temperature, dewpoint)
     assert_almost_equal(mucape, 75.7340825 * units('joule / kilogram'), 6)
-    assert_almost_equal(mucin, -89.8179205 * units('joule / kilogram'), 6)
+    assert_almost_equal(mucin, -136.607809 * units('joule / kilogram'), 6)
 
 
 def test_most_unstable_cape_cin():

diff --git a/metpy/calc/thermo.py b/metpy/calc/thermo.py
@@ -1774,13 +1774,19 @@ def most_unstable_cape_cin(pressure, temperature, dewpoint, **kwargs):
     cape_cin, most_unstable_parcel, parcel_profile
 
     """
-    _, parcel_temperature, parcel_dewpoint, parcel_idx = most_unstable_parcel(pressure,
-                                                                              temperature,
-                                                                              dewpoint,
-                                                                              **kwargs)
-    mu_profile = parcel_profile(pressure[parcel_idx:], parcel_temperature, parcel_dewpoint)
-    return cape_cin(pressure[parcel_idx:], temperature[parcel_idx:],
-                    dewpoint[parcel_idx:], mu_profile)
+    parcel_pressure, parcel_temperature, parcel_dewpoint, parcel_idx = \
+        most_unstable_parcel(pressure, temperature, dewpoint, **kwargs)
+    lcl_pressure, _ = lcl(pressure[0], temperature[0], dewpoint[0])
+    if parcel_pressure > lcl_pressure:
+        p, t, td, mu_profile = parcel_profile_with_lcl(pressure[parcel_idx:],
+                                                       temperature[parcel_idx:],
+                                                       dewpoint[parcel_idx:])
+        return cape_cin(p, t, td, mu_profile)
+    else:
+        mu_profile = parcel_profile(pressure[parcel_idx:], parcel_temperature,
+                                    parcel_dewpoint)
+        return cape_cin(pressure[parcel_idx:], temperature[parcel_idx:],
+                        dewpoint[parcel_idx:], mu_profile)
 
 
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