Excerpt from HPC discussion is quite interesting

[Stormsfury]

HPC noticing ...

D+3 TO 11 PATTERN SUGGESTS WESTERLY CORE TO REMAINING N
COMING IN N OF 45 N AND RUNNING E ALONG THE CANADIAN BORDER.
ATLC SUBTROP RIDGE EXTENDS FROM THE AFRICAN COAST WWD
THRU THE SERN U.S. AND WWD TO BAJA. THIS LEAVES A NEARLY WWD
SRN EDGE OF THE RIDGE FROM AFRICA INTO THE ANTILLES FOR ANY
POTENTIAL TROPICAL SYSTEMS TO TRACK UPON.

TROPICS...LONGER TERM MODEL RUNS OF GFS AND UKMET BEGIN TO
LIKE ERN ATLC SYSTEMS AS THEY KEY ON ONE CURRENT WAVE IN
THE FAR ERN TROP ATLC AND ANOTHER CURRENTLY COMING OFF THE
AFRICAN COAST WITH SIG MODEL DEVELOPMENT. GFS HAS NOT DONE
THIS FOR QUITE SOME TIME. 00Z UKMET RUN SIMILAR WITH BOTH
SYSTEMS. EVEN THE ECMWF CAN FIND AND DEVELOP BOTH OF THE
SYSTEMS THAT GFS AND UKMET HAVE. CONSENSUS OF MODEL
GENERATED DEVELOPMENT AND SOMETHING TO KEY UPON STRONG
INDICATOR OF NEAR FUTURE TROPICAL ACTIVITY DURING MEDIUM
RANGE PERIOD AND BEYOND.

[BEER980]

Yea if you look at the 10 day out model of the GFS you can see 3 of them
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _240.shtml