The picture is much clearer today. The first (Monday) storm will be stronger than thought yesterday but the second (late Tues) storm will not be a threat. The Monday storm is just now “bombing” off HAT, see the satellite image below. The presence of cumulonimbus in the images shows that this is a very energetic storm.
Weather on the Cape deteriorates quickly this evening. NE winds to near gale force, with gusts well above the gale threshold of 35 kts, begin around midnight tonight and continue to early evening Monday when they will back to the NNW and diminish.
Two issues affecting the Cape:
(1) The forecast models haven’t changed the track of the storm on Monday, its center will remain well offshore, but the forecast strength of the storm has increased and, in particular, the radius of strong winds (and thus high seas) is very large. As a result, sea state forecasts from the NWS have been steadily increasing and now peak at 14-19′ for the near shore waters east of Cape Cod late Monday. The storm surge forecast increased as well to 1.5-2′. The time of most concern for erosion will be the Monday morning high tide.
(2) Snow fall amounts: Earlier this week forecast snow totals were not so exciting but the most recent forecasts average out at around 8-10″ for the Cape. The key factor here will be “ocean effect” snow. Like the “lake effect”, this results from warm moist ocean air riding into very cold land areas. Right now ocean temperatures are warm (compared to average) at ~ 6C. Temperatures at ~ 1.5 km aloft will be ~ -8C. This is above the threshold for serious snow. The question for Chatham is whether the snow will dump immediately on land or take until the other side of the Bridges to dump. No answer to that right now – will just have to follow the radar as it develops.