Dan’s Wild Wild Science Journal

I enjoy the stories but the day to day forecast is worthless.

I always enjoy reading the stories in the Farmers Almanac. It’s been around for a LONG time and they have good basic astronomical info in it. Although you can get much more precise info from free programs like Stellarium.

About this time every year they release their forecast for the upcoming winter. TV stations everywhere gobble it up and do news stories on what the coming winter will be like.

Great free publicity!

Just to be clear here, the day to day forecasts are made up. They will not have any accuracy over that of a pure guess.

Some real science: An average of all moderate to strong La Nina's shows a milder than normal winter for much of the U.S. and Eastern Canada.

If you want to know what the winter will be like, the only think I can tell you is that with a moderate to strong La Nina brewing, the Southeast will likely have a drier and slightly milder than  normal winter. The odds of this are about 65%. That means there is a 35% chance it will be colder than normal here!

Other parts of the country will vary. See the graphics.

This kind of long range forecast is only possible because the La Nina pattern of colder than normal water in the Equatorial Pacific will cause a fairly predictable shift in the storm track over North America. The affects will actually be felt world wide.

Temperature anomalies for January during La Nina events. Images from NOAA. Click for full size image.

However, not every La Nina winter is the same. Each one is slightly different. Sometimes the La Nina pattern will hardly show up at all in some areas. Sometimes the expected warm areas are super warm.

The temperature anomalies in January for La Nina years shows that it’s quite warm in the Southeast U.S. most of the time but not always. The La Nina winters of 1971 and 1976 were slightly below normal over the Eastern U.S.

A scientific forecast would be for a good chance of having a mild winter in the Southeast. For those of you in Western Canada, a colder than normal winter seems like a good bet. Sometimes it is a super cold winter as well.

Just what you folks in Edmonton wanted to hear, isn’t it!

Later,
Dan

Hurricane Danielle in the Mid Atlantic and a strong tropical wave near the coast of Africa. Image from Meteosat (Dundee Univrsity ground station).

We are now in the peak of the hurricane season and the Tropical Atlantic is heating up. The second hurricane of the season formed this afternoon in the mid Atlantic.

Hurricane Danielle will likely re-curve though and not affect North America. There is a slight chance of it approaching the NE coast of the U.S. or Canada.

More interesting is the strong tropical wave coming off of Africa behind it. Satellite images this evening show that it is very organized and we will likely see a tropical depression form soon after it gets away from the coast of Africa.

Dan

NASA Modis image of tropical disturbance off of Florida. Pressures are dropping and upper level winds are favourable for development.

There are strong signs that the area of disturbed weather in the Gulf is beginning to get organized today. Pressures are dropping and there seems to be a circulation already present. I suspect the the folks at the NHC in Miami will begin advisories on it later today.

Tropical Cyclone heat potential is based on the depth of the warm water, not just the surface sea water temp.

If it makes it to tropical storm strength it will be named Danielle.

While it is a bit early to talk about the track, the GFDL model is indicating that a landfall somewhere around Louisiana or Mississippi is possible late Friday night. Keep in mind, that the steering currents are very weak and this could change dramatically.

HOW STRONG COULD IT GET?

Could this system reach hurricane status? Yes, but it would be tough to get that strong by landfall. The Gulf is very warm but the tropical cyclone heat potential is not overly impressive. Still it is near the Gulf loop current and that may be helpful.

A good tropical storm may actually be quite helpful to farmers in the southeast who are suffering through an intense heatwave and drought. It’s 37.5C here in Huntsville as I type this.

That’s 100°F on the old scale.

More soon…

Dan

Colder than normal water is already appearing in the Equatorial Pacific (NOAA)

One of the reasons for the forecasts of a an active hurricane season is the predictions that La Nina would develop this summer. Remember that La Nina is an ocean circulation phase that brings unusually cold water to the surface of the Tropical Pacific.

These are the temperature probabilities for a normal/above/below normal autumn (September through Novermber). Click for full resolution image.

Well, it has started and most of the ocean atmosphere models are predicting a moderate to strong event.

This has more impact than just the number of hurricanes. NOAA revised their 2010 hurricane prediction down somewhat today but they are still predicting a 70% chance of 4-6 major hurricanes (Earlier typo said 406- that would be exceptionally bad ). La Nina is a big factor in that.

The colder tropical waters cause a shift in the jet stream. This makes it possible to make a decent prediction of the fall and winter ahead. Here in the Southeastern USA we tend to have a dry fall with normal to above normal  temps. The winter tends to be drier than  normal and sometimes a bit on the mild side.

What about where you live?
The chart at the right shows the probabilities for temperatures during a La Nina event. The image is for the period from September through November.

Take a look at the Northeast USA and Eastern Canada. The chart shows that during a La Nina year the odds are VERY low that the autumn will be below normal. The odds are higher that it will be near normal and the odds are higher still that it will be a warm autumn.

This does not mean that it will not be colder than normal. It just means that in the past this happened rarely.

You can see more of these graphics for your part of the world at the IRI website here. Precipitation maps are also available.

Hurricane Darby in the Pacific (120 mph sustained winds) and a tropical wave south of cuba that may be developing. NOAA GOES image.

It seems we may have our first Atlantic Basin tropical system forming this evening. I’ve been here in Miami all week at the annual AMS Conference on Broadcast Meteorology. This is the 38th Broadcast Conference and one of the best I’ve attended.

The Director of the National Hurricane Center and many of their forecasters put on an excellent seminar Wednesday on tropical meteorology.  Director Bill Read also spoke at our luncheon today.

View from my room of Miami Beach.

The NOAA forecasters and broadcast meteorologists like myself know how important our jobs are in hurricane season. It really is helpful to both groups to understand the problems we each face. Many are very similar and some are rather different.

Tonight, we’re all interested in a system that seems to be organizing in the Western Caribbean. An Air Force Reserve plane is currently investigating to see if a tropical depression has formed.

With a La Nina brewing and record warm waters in the oceans, a late June storm would not be surprising. We get one about 50% of the time. Most of the hurricanes form after August 1st each year.

It’s too early to say much about this system but if it forms it might enter the western Gulf in a few days. Swell from a storm would likely have a big impact on the work around the oil spill, so this could be of extreme importance.

I met the Director of the NHC for the first time today. Say what you will about government, but they got the right man for that job. The forecasters and researchers who work under him are top notch as well, and all of the broadcasters were VERY appreciative of the tremendous seminar and presentations the hurricane specialists put together.

Without doubt we all have one thing in common. We are all very passionate about giving the best information possible to the public.

I’ll post an update if the plane finds a closed circulation.

Update 7:22 PM EDT Fri 25 June:

The recon plane has found a closed circulation and the NHC has begun advisories on TD One. The latest probabilities on tropical storm force winds are below:

From NOAA/TPC/NHC Forecast from Friday evening. Do not use after tonight.

More soon.