Signs of Autumn

2006-08-06 07:13:20.000 – Tim Markle,  Chief Observer

The Summit from Mt. Clay

One of the more important tools we use up here to help us in preparing the higher summits forecast is something called MOS, or Model Output Statistics. It is a numerical forecasting tool that uses a blend of computer models and climatology to determine what the weather may be up here for any given day. Of late, the MOS products have shown strings of unseasonably mild and humid air, even for the summit. In fact, the possible obscuration section of these numerical models have indicated haze on many an occasion. Almost always, these obscurations are listed as mist or fog, or in winter, blowing snow. This week, a cooling trend has been noticed. Where the models were once forecasting highs in the 60s, they are now showing highs in the 40s and 50s. There is even a scattering of mid 30s for overnight lows!

Yes, the seasons are slowly and subtly changing. The signs are not just in the MOS products, but in the hue of the sedge grass; a change in color from its vibrant, summer green to a muted, autumn brown. Changes are also felt with the passing crisp air. Breath, white like chimney smoke, escapes from ones mouth. And the observers now search for hats, gloves, and jackets to take the nighttime and early morning readings as wind chills drop into the low and mid 20s.

It is quickly becoming my favorite time to hike. The seasonable chill above treeline offers relief from any lingering summertime valley heat, and haze free sky reveals the scenic views the White Mountains are famous for. I must remember, though, that the summer season is quickly drawing to a close on the Rock Pile, and that conditions up here can be easily less forgiving than locations under the cover of the forest canopy. Now is the time to make sure, that if you plan to hike, you are prepared to come across any weather condition.

Tim Markle,  Chief Observer