Need help tracking down a time adjustment issue

Hey, guys. Thanks for reading. I have logs coming from a Windows event, pulled in by logstash-forwarder and sent to Logstash, where it is then sent to Elasticsearch 2.0.

I have an input as follows:

 tcp {
                codec => json_lines
                port => 5100
                type => "eventlog"
        }

And a filter:

 grok {
                        match => [ "Message", "TransactionID=%{UUID:TransactionID},TransactionRole=%{WORD:TransactionRole},TransactionType=%{WORD:TransactionType},ModalityName=%{WORD:ModalityName},SystemName=%{WORD:SystemName},RequestTimestamp=%{TIMESTAMP_ISO8601:RequestTimestamp},Duration=%{BASE10NUM:Duration}" ]
}

And an output:

 elasticsearch {
                        hosts    => "10.xxx.xxx.xxx"
                        index => "logstash-myindex-%{+YYYY.MM.dd}"
                }

An example message looks like:

TransactionID=placeholder,TransactionRole=Server,TransactionType=ITI_8,ModalityName=placeholder,SystemName=placeholder,RequestTimestamp=2016-01-19T09:08:28,Duration=171.6033

This creates a separate date field (besides @timestamp) named RequestTimestamp with "2016-01-19T09:08:28." However, in Kibana 4, RequestTimestamp shows up as "January 19th 2016, 03:08:28.000," even with the timezone setting is on "browser." Also in Kibana, the original time in the message shows "2016-01-19T09:08:28." So my question is, where is the offset getting applied and how do I compensate? It looks like it's being converted to UTC twice...

LS assumes UTC by default, as does ES.
KB reads that (so assumes UTC) but converts to local to display it.

Are your logs coming in as UTC?