Tropical weather analysis - June 12, 2010

A vigorous tropical wave, more typical of early August than June, has just been designated "Invest 92L" by the National Hurricane Center.

The last of the visible satellite animations indicate that the axis of this wave is located near 6N 31W. Extrapolation of an earlier ASCAT pass would also yield this estimate. Surface winds are probably around 20-25 mph near the estimated center position. Vertical shear over the system is light, around 10 kt. Vertical shear is forecast to be marginally favorable for slow development of this system for the next 60 hours or so, after which point, the system should encounter strong upper-level westerlies associated with a large and persistent TUTT (Tropical Upper Tropospheric Trough) centered across the central Caribbean Sea. As far as movement is concerned, the system is currently moving slowly WNW, and this should continue throughout the forecast period. This will bring the system near the Leeward Islands and Puerto Rico by around 6 days.

This system only has around 60 hours to coalesce into a tropical cyclone, so we'll see how that goes. Water vapor loops indicate that dry air within the vicinity of the system is fairly minimal at the moment. Obviously, this will tend to favor continued intensification in the short-term, though we'll have to see how moist the environment stays over the next couple of days. As long as the convection continues to be enhanced by the ITCZ, as is currently the case, then the overall environment should remain rather moist, and favor additional development.

All in all, I'd give this system a 20% chance of becoming a tropical cyclone over the next 48 hours. It should be noted that anything higher than a 35 kt tropical storm looks terribly unlikely. However, the significance of this wave lies not in its possible intensity, but rather, it's possible development. If it develops into a tropical cyclone, named or otherwise, then we are very likely in for a very active season ahead, as any time we get tropical cyclones in the deep tropics during June and July, it is almost always a harbinger of an above normal season. This was most recently the case in 2008 with Hurricane Bertha, and before that, in 2000, when Tropical Depression Two formed just offshore western Africa during the final days of June. Both of those seasons were well above average.

None of the computer models are developing this area, but it bears watching. Climatology would certainly argue against it, however.