Unable to download latest artifact from snapshot repository

node('cdPipeline'){
def server = Artifactory.server "artifactory_lower_prod_server"
def downloadSpec = """{
"files": [
{

"pattern": "snapshot-local/<PATH>/2018.01.0-SNAPSHOT/wibtp-zelle-2018.01.0-SNAPSHOT.tar",
"target": "/var/tmp/kiran/",
"flat": true

}
]
}
}"""
println(downloadSpec)
server.download(downloadSpec)

}

This works well with release repositories, as the tar file pattern would be *tar