A new study on predicting maximum hurricane intensity using lightning

David L. Hagen writes in with an interesting new paper, Maximum hurricane intensity preceded by increase in lightning frequency (PDF). I find it fascinating.

It was published in Nature Geoscience on April 6th, 2009 by Colin Price, Mustafa Asfur, and Yoav Yair. Price is from the Department of Geophysics and Planetary Sciences, Tel Aviv University while Asfur and Yair are from the Department of Life and Natural Sciences, The Open University of Israel.

The abstract reads:

Hurricanes are the Earth’s most deadly storms, causing tremendous devastation around the globe every year. Forecasters are quite successful in predicting the pathways of hurricanes days in advance1, but hurricane intensification is less accurately predicted. Here we analyse the evolution of maximum winds and total lightning frequency every 6 h during the entire lifetime of 56 hurricanes around the globe. We find that in all of these hurricanes, lightning frequency and maximum sustained winds are significantly correlated (mean correlation coefficient of 0.82), where the maximum sustained winds and minimum pressures in hurricanes are preceded by increases in lightning activity approximately one day before the peak winds. We suggest that increases in lightning activity in hurricanes are related to enhanced convection that increases the rate of moistening of the lower troposphere, which in turn leads to the intensification of hurricanes2. As lightning activity can now be monitored continuously in hurricanes at any location around the globe, lightning data may contribute to better hurricane forecasts in the future.

The premise makes sense, because lightning is essentially a proxy for energy release of a storm. As the authors write: “Lightning is directly related to thermodynamic processes that result in the release of latent heat in convective clouds”, though it is not always an exact proxy. Cumulonimbus vary their lightning out based on many other atmospheric factors also. Even so, there seems to be both statistical and anecdotal correlations for the premise of lightning frequency to hurricane intensity.

The authors write:

Although for many years hurricanes were believed to have little lightning activity, lightning has been observed within many hurricanes. Even some historical anecdotes from sailors describe intense lightning in hurricanes15: “For one whole day and night it blazed like a furnace, and the lightning broke forth with such violence that each time I wondered if it had carried off my spars and sails; the flashes came with such fury and frightfulness that we all thought the ships would be blasted”. Recently, lightning activity in tropical waves has also been related to the genesis of hurricanes.

To check the connection between hurricane intensification and electrical activity, we have collected data from all 58 category-4 and category-5 (Saffir-Simpson scale) hurricanes around the globe over a three-year period (2005-2007) (Fig. 1; see Methods). By definition, these storms have maximum sustained horizontal winds greater than 114 knots (210 km h). The two main centres of hurricane activity occurred in the west Pacific and the west Atlantic. However, intense hurricanes also occurred in the Indian Ocean and southern/eastern Pacific.

From the paper:

The statistical significance of these fits is shown in Fig. 4, where

the linear correlation coefficients (r) between the lightning activity

and wind speeds are shown for each hurricane, taking into account

the lags shown in Fig. 3. The names of the 56 hurricanes are shown

along the x axis, and the correlation coefficients are shown with

different symbols depending on their statistical significance. The

significance was calculated on the basis of the number of days

used in the analysis for each hurricane. Hence, two hurricanes

with the same correlation coefficient can have different statistical

significance. All 56 hurricanes show significant correlations

(>90%) between lightning activity and maximum sustained winds,

with a mean of r D0:82. This implies that daily lightning frequencies

can explain more than 67% of the daily variability in maximum

sustained winds, with an average lead time of 30 h.

And also:

Of the 58 hurricanes analysed, only 2 showed no significant

correlation between lightning and wind speed. One of these

hurricanes (Ingrid 2005) showed no lightning at all, whereas the

other (Kirogi 2005) had two maxima in the wind speeds and

lightning, but the larger maxima in the wind speeds was correlated

with the weaker peak of the lightning activity (see Supplementary

Information S2). Hence, only one event showed no relationship

between lightning and maximum wind speed. If we consider a

constant lag of 30 h between the lightning activity and the maximum

winds in all hurricanes, we find that 31 out of 56 (55%) of the

hurricanes show a positive correlation between lightning and wind

speed, although only 19 out of 56 (34%) of the hurricanes show a

statistically significant correlation for a fixed lag.

Interesting research. When we get improved lightning detection systems this may be a valuable tool. Unfortunately, NOAA has fallen down on the job related to this, while NOAA has an excellent (best in the world) NEXRAD Doppler Radar Network, they have no lightning detection network at all. Private companies have filled the gap, and they charge exorbitant sums and have draconian licensing schemes. I cite this from experience.

With all of the stimulus money being thrown around at NOAA, you’d think they’d do this, particularly since lightning accounts for a significant amount of deaths, injuries, and property damage in the USA each year.

The following maps and tables show state-by-state lightning deaths from 1990 to 2003 based on Storm Data compiled by Ronald L. Holle, Meteorologist/Consultant at Vaisala Inc.  He notes there is a continuing shift to the south and west in death rates caused by lightning.

Source: National Lightning Safety Institute

http://www.lightningsafety.com/nlsi_lls/fatalities_us.html