Monday, August 01, 2011

Random Weather notes, the tropics and the heat

August is here.

Summer is going fast.  Yet there is alot to talk about weatherwise as the summer peaks and hurricane season continues to rapidly develop.  So this post on Scott's World of Weather will be a hodge-podge of topics.

First, my 90 degree prediction of "7 days".  Yep, it went up in smoke a week and a half ago.  There were several reasons for my busted prediction.  The first was the over-emphasis of the massive spring rainfall.  We had the wettest April/May period on record.  Usually, wet ground keeps high temperatures down a bit.  This did happen in the spring and early summer (June).  Average temps (day and night combined) in June were a notch below 70. For comparison, the 10th coolest month was June of 1902 with an average temp of 62.  We did have one day above 90 on June 4th.

The second reason was the underestimation of the strength of heat ridge in the middle of the country.  The La Nina winter/spring we had had a cooling effect on the atmosphere across the country.  Droughts in Oklahoma and Texas are common in these summers after a La Nina.

This drought promoted further growth of the ridge of heat. The moist ground and the trough over Ohio kept the ridge from pushing east.  Eventually in July, the trough flattened and the ridge slid into Ohio and the Great Lakes in an albeit weaker state.  The result was a burst of heat that culminated in 6 quick 90 degree days which killed my prediction by July 21st.  The high that day was 97, the hottest day in Cleveland since 1995.

The third was my overemphasizing of the MJO.  The MJO or the Madden Julian Oscillation is the cyclical movement of tropical convection that can directly influence the position of the jet stream in North America. CLICK TO ANIMATE THE IMAGE

Without going into too much detail, it seemed that the MJO reacted in such a way as to promote more eastward warmth than eastward "cooling". Again, it wasn't the strongest MJO signal but could have played a small part.


As for the temperature numbers, here are the number of 80 and 90 degree days through July 31st over the last 5 summers:

Now for the tropics.  Tropical storm EMILY is now churning in the Caribbean as I write this.

The forecast brings this system very close to the US coastline by the end of the week.

The origin of hurricanes which make US landfall show most of them develop in the Gulf of Mexico