Friday, March 6, 2015

Tropical Cyclone 15S [updated]

Tropical Cyclone 15S is currently in the Mozambique Channel, as shown by the image above from NASA's Terra satellite processed by the NASA Goddard MODIS Rapid Response Team. The image was acquired at 10:40 East Africa Time on March 6th.

Will the circulation associated with 15S influence Kilimanjaro snowfall? We will be keeping an eye on this, for the circulation around prior cyclones seems to have been associated with precipitation at this time of year - as moisture is delivered from the Congo Basin. Here is a previous discussion, initiated by conversations with Timba at Ahsante Tours & Safaris.

Forecasters at the Joint Typhoon Warning Center anticipate 15S wind speeds to increase over the next few days. The duration that the cyclone remains over warm water may determine the impact on Kilimanjaro. We will provide an update next week!

 [UPDATE 3/11:  No apparent influence this time. Mid-tropospheric circulation to the north (i.e., Kilimanjaro) seems not to have been substantially influenced by 15S, and westerly flow never developed. We'll keep an eye on future cyclones this season.]

Wednesday, March 4, 2015

February snow

February on Kilimanjaro is typically a rather dry month, a mini dry season sandwiched between the short-rains of roughly November-December, and the long-rains during the March-April-May period. Last month followed this pattern, excepting a brief, important event occurring mid-month.

At the summit, snowfall began late on the 14th and appears to have continued all day on the 15th. The 16th may have been dry in the morning, but by evening telemetry data suggest that snowfall began again, with increased wind speed that may have caused drifting of the fresh snow. Reports from climbers on the mountain mention heavy snowfall at Arrow Glacier Camp and in the Western Breach. By early on the 18th the event was over and dry conditions again prevailed on into early March.

This February event is important because it was the largest snowfall event since the long-rains of 2014, totaling 16.5 cm. This is ~2 cm greater than the event of late-November into early-December 2014. Although events of this magnitude pale in comparison with those on other mountains, they must be viewed in context; the summit of Kilimanjaro is very dry. Snowfall on the summit glaciers adds mass to horizontal surfaces, and more importantly - a bright, smooth snow surface changes the energy balance both on the glaciers and on surrounding caldera surfaces adjacent to the vertical walls.