Demons and Butterflies

Beating predictability theory--long-range forecasts of hurricanes by 2025?

Richard Anthes

VI Congreso Cubano de Meteorologia30 November 2011

"Everything proceeds mathematically . . . if someone could have a sufficient insight into the inner parts of things, and in addition had remembrance and intelligence enough to consider all the circumstances and take them into account, he would be a prophet and see the future in the present as in a mirror."Gottfried Leibniz (1646-1716)

The Marquis de Laplace dreamed of an intelligent being (an intellect, later dubbed Laplace's Demon) who knew the positions and velocities of every single atom and used Newton's equations of motion to predict the future of the entire universe.

Pierre-Simon Laplace (1749-1827)

"We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at any given moment knew all of the forces that animate nature and the mutual positions of the beings that compose it, if this intellect were vast enough to submit the data to analysis, could condense into a single formula the movement of the greatest bodies of the universe and that of the lightest atom; for such an intellect nothing could be uncertain and the future just like the past would be present before its eyes."

Niels Bohr (1885-1962)

“Prediction is difficult,especially the future.”

Does the flap of a butterfly’s wing in Brazil set off a tornado in Texas?

“It is doubtful whether a sufficient number of simultaneous initial observations will ever beavailable … for these scales, although somemesoscale variability may be revealed by satellites.However, nonlinear processes are capable ofproducing smaller scale information in the forecastthan is present in the initial conditions, as longwaves interact to produce energy in shorter waves. Furthermore, a realistic treatment of local forcingin the models will allow mesoscale perturbations todevelop from initial conditions that are representativeof larger scales. Thus we hypothesize that in manysynoptic situations, if the local forcing is modeledcorrectly, the details of the initial perturbations arenot particularly important.”

Anthes and WarnerMonthly Weather Review, August 1978

But scale interactions go both ways!

Examples of medium- and long-range predictions of hurricanes

Hurricane Katrina 2005

Katrina eyewallCat. 5

28 Aug 2005

11

How much more accurate can hurricane forecasts become?Can they be forecast a month in advance?

Hurricane Katrina 2005WRF initialized 00 UTC 27 AugComposite Radar Observations

72 h forecast

Tropical cyclone formation in climate model “September 2000”

NCAR’s WRF nested within the Earth System Model starting January 1, 1995Courtesy Cindy Bruyere and Greg Holland, NCAR

Bo-Wen Shen et al., JGR, 115, D14102, doi:10.1029/2009JD013140, 2010

5-day forecast of genesis of Cyclone Nargis (2008)00GMT 22 Apr-00UTC 29 Apr

10 year statistics 1996 - 2005

Improved high resolution climate models can predictcorrect frequency of tropical cyclone formation

New Observations can improve predictions

Impact of GPS Radio Occultation Data on Tropical Cyclone Genesis

Hurricane Ernesto2006

Radio Occultation-A new way of obtaining accurate and precise profiles of temperature and water vapor in all weather

NCAR 4-Day Ernesto (2006) Forecasts

NCAR 4-Day Ernesto (2006) Forecasts

Y.-H. Kuo (NCAR), 2007

Forecast with GPSForecast with GPS Forecast without GPSForecast without GPSThe Actual StormThe Actual Storm

Caribbean Ground-based GPS Network

Under NSF sponsorship, UCAR has established a ground-based GPS network over the Caribbean to support hurricane research.

The color-coded PW estimates from GPS stations in the Caribbean, Gulf of Mexico, and Mexico are overlaid upon a GOES infrared channel 4 (IR4) image on September 1, 2008. In this image, hurricane Gustav is approaching the Louisiana coast and tropical storm Hanna is positioned over Grand Turk.

Summary• There is evidence that greatly improved

forecasts of tropical cyclone tracks and intensity are predictable days in advance

• Realizing this potential will require– High-resolution global models—probably 4 km or better– Improved physics in models—cloud physics and

radiation– Interactive ocean-atmosphere models– Improved initial conditions in atmospheric temperature,

water vapor and winds-satellite observations– Improved data assimilation techniques– Faster computers

Thank you!