|WHAT IS MEANT BY A “FLY IN THE OINTMENT” WHEN FORECASTING?
METEOROLOGIST JEFF HABY
The phrase “fly in the ointment” is one of the favorites of many forecasters. It perfectly describes the issues that have to be faced when weather
forecasting. The phrase refers to a particular variable that is making the forecast more difficult to make. It could be cloud cover, solar heating,
amount of lift, strength of capping inversion, temperature profile, amount of instability, wind shear, amount of low level moisture, or any other
variable that is making the forecast difficult. For example, there could be explosive convection when storms form but the cap looks like it
might just be strong enough to prevent storms. The situation is so close though that it is difficult to have any kind of certainty one way
or another. A forecaster in this situation is limited in that the storms need to be mentioned but they may not happen at all. A fly in the
ointment commonly occurs with winter storm forecasts. There are extra variables when forecasting winter storms such as precipitation type(s),
low pressure intensity/track, amount of ice/snow accumulation and travel disruptions. The temperature profile could be right on the border
of one precipitation type or another. The lifting may be right on the edge between having enough to produce freezing rain and no precipitation
occurring. The forecaster will have to mention the icing potential but nothing may happen. Generally when making a forecast, there will
be one or more variables that make the forecast more complicated. These variables are “flies in the ointment”.