It'a About to Get Interesting - Thursday Update

THU 5/8: While May nor'easters are not entirely unheard of, they are certainly less common than one in the winter or early spring months. Ordinarily, by this time of year, the jet stream has settled down (and shifted north) and the atmosphere doesn't have the strong contrasts in air masses to feed off of in order to fuel an intensifying storm center in the mid-latitudes. Still, when conditions are right, they can happen and over the next week or so, we actually may have several to look at.

Friday's storm still appears rather impressive, with the run after run of the NAM and GFS computer models consistently hitting Cape Cod with a heavy slug of rain and plenty of wind.

The NAM (outside of its ridiculous 06z run that produced over 6" of rain at Chatham) continues to dump between 2.5 and 3.5" of rain around the area by the time things settle down Saturday morning. The GFS is a bit drier, but still produces 1.5 to 2.5" of water - with most of this falling between say 5PM and 1AM Friday Night. (The 12z hi-res NMM produces *a lot* more water fwiw)

The wind situation is quiet interesting. Both models show unusually strong low level winds, with greater than 50 knot NE winds cranking in the lowest few thousand feet of the atmosphere. The atmosphere won't be remarkably unstable, but we could easily gust past 40 mph and sustained speeds could surpass 30mph Friday night. The wind will help build seas and pile up water along east facing shores, certainly not helping the situation for places like Nantucket and Chatham where any beach erosion is unwelcome news for many.

If this isn't enough for you, there's plenty more with this came from, with another big rain/wind event possible Monday or Tuesday, with another wet system possible Thursday!

WED 5/7: Get out there and enjoy Wednesday's nice weather as we are about to go backwards a month (or two) in the weather pattern. Things are going to turn quite stormy and quite ugly around here over the next 5 to 7 days (starting in earnest on Friday) as a negative North Atlantic Oscillation comes on strong and combines with the warmth of May to produce several sizable storms. By the time this stretch of nasty weather ends, rainfall should be measured in inches, coastal flooding and beach erosion will have been a problem, and temperatures are going to average out much too chilly for May. This overall weather pattern may have some implications on our coastal waters as well, with the threat for a large-scale Red Tide outbreak looming large.

Storm # 1: Two pieces of energy embedded in the jet stream are going to merge over the Northeast and fuel an intensifying surface storm off the Jersey shore late this week. On Monday I wrote about this potential "mini-nor'easter" but mentioned some reluctance to go overboard given the time of year. However, all model guidance is on board at this point, spinning a 992 mb low (or deeper) south of Cape Cod in a traditional winter-like fashion. On its journey eastward across the nation, this storm will tap plenty of Gulf of Mexico moisture and fire up numerous showers and thunderstorms. This moisture/energy will get carried eastward and instead of fizzling out as it nears, will be aided by a strong influx of Atlantic moisture when the storm hits the East Coast. This has the makings for a good ol' fashion soaking, with at least 1 to 2 inches of rain expected around the area - perhaps closer to 3" should the heaviest axis of rain set up over the Cape.

Along with the heavy rain, strong easterly winds (again relative to the time of year) are likely to develop around the area during course of the day on Friday and last into Saturday afternoon (gradually shifting to the northeast, then north, then northwest with time). On the open waters, gale force winds are a distinct possibility, with gusts to 40 knots not out of the question. Here on the Cape, wind gusts to 35 mph are likely at times, creating a wind driven rain Friday night. With gusty onshore winds and a high Saturday morning (around 3AM) high tide some beach erosion is likely, with perhaps some minor coastal flooding in vulnerable spots.

Storm # 2: We get a break in the action on Sunday, but it should be short-lived as yet another anomalous storm system appears to head our way early next week. The aforementioned North Atlantic Oscillation will really begin to take shape, driving unusually low upper level heights across the Eastern United States, pushing a pool of cold air down from the arctic and fueling another strong storm system over the east (be very thankful its May, not January or February or we'd be talking major winter storms here.) This second storm, while still a good 5 days away may actually end up a bit stronger than its predecessor, with the central pressure possibly dipping below 990 mb. In the winter season, these numbers are not overly impressive - but during the warmer months, in my opinion, anything that's non-tropical and under 998 mb is notable. Regardless, this second storm again has the potential to bring heavy rains and strong winds, depending upon its ultimate track and exact intensity (which it is still way too early to call.) With the system becoming vertically stacked, it may stall or slow to a crawl to our south and east, keeping things unsettled Monday through Wednesday as well!

On the larger, macro-scale, this second system looks far more impressive than the Friday/Saturday storm - likely affecting a much larger region and bringing a much larger swath of bad weather. This storm will likely be another big severe weather producer in parts of the country and believe-it-or-not, could bring snow to higher elevations in the Northeast. However, locally, here on the Cape, it remains to be seen which of the two systems has the greater impact. This will be highly dependent upon just how the upper level jet streams ultimately configure themselves. Either way, its going to be a stormy period.

Red Tide: This brings me back to the last sentence of the opening paragraph and the reference to a possible link to Red Tide. If we go back to May of 2005, when the region saw a record (and really nationally recognized) outbreak of Red Tide, we see some interesting similarities. Two unusually strong, cold systems hit the region, one at the beginning of the month and the other near the end of the month. Much of the region saw well over 6 inches of rain that May and the two nor'easters brought strong onshore winds, high tides and beach erosion. I submit this to you: http://www.hpc.ncep.noaa.gov/dailywxmap/index_20050508.html and particularly this: http://www.hpc.ncep.noaa.gov/dailywxmap/dwm_500ht_20050508.html. Thats a look at the surface and upper level weather set-up during the first of two nor'easters that hit the area in May of 2005 (thats the 8th of May by the way - what's the date today??)

Now keep that open and here is a look at the European model's forecast come Wednesday of next week after the second storm of this current series: Amazingly similar. Should we maintain a long onshore flow, heavy rain and add in the addition of snow melt from the mountains of Maine, and the set up is not too different from several years. We know from WHOI research that this year could be a bad year given the 'right" (wrong??) conditions. Time will tell I suppose.