1. ‘Son of Juan’
Precipitation system that hit Nova Scotia 6 to 12 hours after Juan’s impact
Produced more precipitation than that of Juan in Shearwater, NS (~30 mm)

2. Improved Guidance
How much could have been done in real time at high resolution?

3. Change of North American flow at the DT from 21/00 to 23/12:
The dominant broad trough in N. America is replaced by a primarily zonal flow, with a short wavelength ridge-trough couplet over eastern N. America. A warm anomaly travels across the continent, reinvigorated by convection, to amplify the eastern ridge.
21/00
23/12

4. 0000 UTC, 24 Sept. 2003
Note the stationary warm ridge over Nova Scotia, polar jet at US-Canada border and ST jet over southern US

5. 1200 UTC, 25 Sept. 2003
Short-wave ripples appear along the ST jet, as the midwestern trough digs southeastward

6. Note the reversal of the meridional PV gradient, indicating a barotropic instability

7. 1200 UTC, 26 Sept. 2003

8. 27/00; Son of Juan lies west of Florida; easternmost convection at 35 N, 65 W interacts with Juan

9. 0000 UTC, 29 Sept. 2003
Both Juan and son of Juan accelerate poleward under the infliuence of the persistent, amplified ridge-trough couplet

10. 1200 UTC, 29 Sept. 2003
Note Juan’s maintenance of its tropical characteristics, and that ‘Son of Juan’ helps to ‘protect’ Juan from the potentially cold air

11. ‘Son of Juan’
Developed in association with a highly-amplified, persistent trough-ridge couplet
Helped to protect Juan from extratropical influences as it traveled into the Maritime provinces
Developed in a barotropically-unstable environment along the Gulf of Mexico coast of the US