Parse the sea-level pressure remark group.

def _handleSealvlPressRemark(self, d):
        """
        Parse the sea-level pressure remark group.
        """
        value = float(d['press']) / 10.0
        if value < 50:
            value += 1000
        else:
            value += 900
        if not self.press:
            self.press = CustomPressure(value)
        self.press_sea_level = CustomPressure(value)