FLS and ACHA in the tropics

Forecasting at the tropical desk can be a challenging task. This week participants continue to explore the graphical forecast idea for the very hazards typically accounted for a in a text Area Forecast (FA) written for the tropics. While drawing out forecasted ceilings this morning, the Fog and Low Stratus and Cloud Top Altitudes products were utilized. These are not forecast products, but the trends in them earlier in the day can be applied to the model information and forecasts for later in the afternoon.

In particular, there was an area of clouds off the coast of the Yucatan. Participants were attempting to determine if the clouds were low enough and persistent enough to warrant a ceiling advisory for later in the day. To this end they first looked at the IFR probabilities.

20150817 1445 UTC IFR probabilities

Probabilities were pretty much zero. To confirm, participants then looked at the cloud top height product, shown below.

20150817 1445 cloud top altitudes at FL180 and below

Note that just west of the Yucatan there were no tops indicated at all. To the north there was an area showing some lower tops, but given the trend of clearing noted in generic visible imagery, it didn't appear as if this trend would last. Model data also seemed to follow this trend for forecasts later in the afternoon.

While cloud ceilings rather than altitudes would have been more useful in this case, using the latter with the IFR probabilities was still a beneficial way to examine current weather and get an idea of future trends.