Add a meteorological tweak

Add a meteorological tweak

remove unwanted env vars

Author: wxtim

cylc/flow/etc/tutorial/cylc-forecasting-workflow/bin/get-observations

@@ -61,6 +61,49 @@ ORDINATES = {
     'NNW': '157.5'
 }
 
+class Meteorology:
+    """
+    Surface winds tend to be 20-30 degrees backed (vector anticlockwise)
+    from the winds which steer weather systems:
+    Friction with the ground surface tends to mean that land surface winds
+    are as slow as half the speed of the wind at 2000ft. This fudge factor is
+    a more conservative 1.5:
+
+    .. seealso::
+
+       [Source Book to the Forecaster's Reference Book](https://digital.nmla
+       .metoffice.gov.uk/IO_011f7cd4-50fc-4903-b556-d24480ea883d/), section
+       1.2
+    """
+    SURFACE_BACKING = 2
+    SURFACE_FRICTION = .66
+    KT_TO_MPH = 1.15078
+
+    @staticmethod
+    def process_direction(direction: str) -> str:
+        """Process raw wind direction:
+
+        * Convert direction from 10s of degrees to degrees.
+        * Convert from Oceanographic (wind to) to Meteorological (wind from)
+          convention.
+        * Surface Friction Correction
+        """
+        return str(
+            ((int(direction) + 18 - Meteorology.SURFACE_BACKING) % 36) * 10)
+
+    @staticmethod
+    def process_speed(speed: str) -> str:
+        """Process Raw wind speed
+
+        * Convert to KT to MPH
+        * Surface Friction Correction
+        """
+        return str(
+            (
+                int(speed) * Meteorology.KT_TO_MPH
+            ) / Meteorology.SURFACE_FRICTION
+        )
+
 
 class NoDataException(Exception):
     ...
@@ -134,10 +177,10 @@ def synop_grab(site_id, time):
 
     # * Parse the direction from 10's of degrees to degrees
     # * Convert direction from to direction it's blowing to
-    data['direction'] = str(((int(data['direction']) + 18) % 36) * 10)
+    data['direction'] = Meteorology.process_direction(data['direction'])
 
     # Convert data in KT to MPH:
-    data['speed'] = str(int(data['speed']) * 1.15078)
+    data['speed'] = Meteorology.process_speed(data['speed'])
 
     # Get lat and long from MO Data:
     lat, lon = reference_lat_long(site_id)

cylc/flow/etc/tutorial/cylc-forecasting-workflow/flow.cylc

@@ -74,13 +74,6 @@
 
     [[get_rainfall]]
         script = get-rainfall
-        [[[environment]]]
-            # A template Map file
-            MAP_FILE = "${CYLC_TASK_LOG_ROOT}-map.html"
-            # Create the html map file in the task's log directory.
-            MAP_FILE = "${CYLC_TASK_LOG_ROOT}-map.html"
-            # The path to the template file used to generate the html map.
-            MAP_TEMPLATE = "$CYLC_WORKFLOW_RUN_DIR/lib/template/map.html"
 
     [[forecast]]
         script = forecast 60 5  # Generate 5 forecasts at 60 minute intervals.