The document discusses three instruments that measured cosmic ray neutron intensity during Hurricane Sandy as it passed through the Northeast US in late October 2012. The instruments included a neutron monitor in Newark, DE and two COSMOS probes, one in Beltsville, MD and the other in Shale Hills, PA. The COSMOS probes responded differently due to one experiencing heavy rainfall whereas the other did not. The Newark monitor showed a response to decreasing atmospheric pressure. Data from all instruments is available online.

1. Lecture  15
Thunderstorm
Tornado
1

2. 2

3. 3

4. If divergence aloft > convergence at
surface, will the low will deepen or
decay?
If divergence aloft < convergence at
surface, will the low will deepen or
decay?

5. Hurricane Sandy in three cosmic-ray neutron records
1000
P re s s u re
U n c o rre c te d n e u tro n s
800
980
700
960
600
P re ssu re , m b
N e u tro n co u n ts p e r h o u r
C O S M O S p ro b e , S h a le H ills , P A
900
Shale Hills
Newark
Beltsville
940
P re s s u re -c o rre c te d n e u tro n s
500
24 O ct
26 O ct
28 O ct
30 O ct
1 Nov
3 Nov
5 Nov
P re s s u re
1020
U n c o rre c te d n e u tro n s
900
1000
800
980
700
P re s s u re -c o rre c te d n e u tro n s
600
24 O ct
26 O ct
28 O ct
30 O ct
1 Nov
N e u tro n M o n ito r, N e w a rk , D E
3 Nov
5 Nov
P re s s u re , m b
N e u tro n c o u n ts p e r h o u r
C O S M O S p ro b e , B e lts ville , M D
1000
960
As the hurricane Sandy (above) passed through the
Northeastern USA, it went over three instruments that
measure cosmic-ray neutron intensity, a neutron monitor
that is sensitive to pressure, and two COSMOS probes that
are sensitive to pressure and surface moisture.
The two COSMOS probes have different responses because
one, Beltsville, experienced large rainfall, whereas the other
did not. More on that on next page. COSMOS data are
available here: cosmos.hwr.arizona.edu. The COSMOS
project is funded by the Atmospheric and Geospace
Sciences Division of the National Science Foundation.
The Newark neutron monitor data show a response to
pressure drop. Data and plot are courtesy of Roger Pyle of
the Bartol Research Institute, University of Delaware.
Neutron monitor data are available here:
http://neutronm.bartol.udel.edu.
Marek Zreda (marek@hwr.arizona.edu)
12

6. Help?

7. Tilt

8. Jet streaks (maximum in jet streams) tend to found in the base of trough
Intensify
convergence
Intensify
divergence
-storm moves northeastward, It no longer
has upper-level support of diverging
air, and storm dies out

9. Rossby waves
4~6 waves
Wavelength
4000~8000 km

10. Thunderstorm Distribution
A climatology of the average number of thunderstorm days in a year
10

11. Thunderstorm

12. Cumulus
Mature
12
Dissipating

13. Fig. 11-10, p. 320

14. Tornado

16. 16

17. Fig. 10-32, p. 288

18.  derived from Spanish word ‘tornada’  thunderstorm
 tornados arise from severe thunderstorms
 most tornados in central US
 on average about 770 tornados are reported annually
 occur mainly from April to June but all year round

19. Fig. 11-23, p. 331

20. Tornados visited NYC on September 16, 2010
The National Weather Service (NWS) said one of the tornadoes touched
down near Park Slope in Brooklyn with maximum wind speeds around 80
miles (129 kilometers) per hour. The second tornado touched down about
2.5 miles (4 kilometers) south of Flushing in Queens and lifted about one
mile (1.6 kilometer) northeast of Bayside. This tornado was slightly
stronger with maximum wind speeds of around 100 miles (161 kilometers)
per hour.
Tornadoes are extremely rare in New York City, and Thursday's tornadoes
were the first time one record that a tornado caused a fatality in the city.
The last time a tornado hit New York City was in July, when a weak tornado
swirled through the Bronx.
Prior to that, two tornadoes touched down in Staten Island and Brooklyn on
August 8, 2007. Other tornadoes touched down in 2003, 1995, 1990, 1985
and 1974. No other tornadoes were recorded since records began in 1950.
http://data.giss.nasa.gov/gistemp/graphs/

22. Q: If you are confronted in an open field by a large tornado and there is no way that you could
outrun it, probably the only thing that you could do would be to run and lie down in a depression. If
given the choice, would you run toward your right or left as the tornado approaches? Explain your
reasoning.
Fig. 11-23, p. 331

24. Something like

25.  produce a rotating column of air by a large wind shear at the
surface
lift the rotating column of air from horizontal to vertical by updraft
Fig. 11-23, p. 331

26. Where is tornado birth-column?
Southwesterly wind
Why overshooting?
Mesocyclone
a single strong
rotating updraft
Rear Flank
Downdraft
Why no prec. In
mesocyclone?
Wall cloud – lower than others – why?

27. Importance of the Rear Flank Downdraft

28. Wall Cloud

29. Tornado structure
Q: in the core of a tornado, is the flow direction upward or downward?
How strong is a tornado?

31. Table 11-3, p. 333