As the satellite image above shows, it is in an area of strong vertical wind shear... in this enhancement, the low-level clouds show up in the yellow shades, while the upper-level clouds are white. The surface center of circulation is completely exposed. It is a minimal tropical storm now (40mph maximum winds), and is forecast to strengthen just slightly as it heads north, then gradually transition to an extratropical cyclone by the weekend.
There are weather satellites in orbit than routinely measure the surface winds over water, they are called scatterometers. One such satellite passed right over Ian this morning and helped justify the upgrade to a tropical storm. In this swath of wind vectors, the center is found toward the bottom, with winds circling counter-clockwise around it.
Climatologically, the 8th named storm forms on September 21, so this is a bit ahead of an "average" year (using a 1981-2010 climatology). If you missed my post about the various climatologies, check out When is the ‘peak’ of hurricane season? It’s more complicated than you think.
However, in terms of ACE, this season is slipping behind, now at about 76% of average for this date.
- Visit the Tropical Atlantic Headquarters.
- Subscribe to get these updates emailed to you.
- Follow me on Twitter