Some Website Updates and A Look at the Next Few Days.

10/3/08: A bit of housekeeping here first:

1. Along or about the 1st and 15th of each month a new article will appear in the maps and charts section discussing the most recent seasonal temperature forecast updates from the CFS (climate forecast system).

2. Interesting weather videos / reports from the AP and independent journalists will be posted to the new weather videos section at least once-a-week so check in with that page every-so-often when big weather events occur somewhere in the U.S. to get some good video updates.

3. Very soon you will be able to sign up for mobile (text messages) weather updates on your cell phone from CapeCodWeather.Net. The same system will allow CapeCodWeather.Net to make frequent, short updates to the site when necessary to pass along any interesting weather news on the Cape. Keep an eye open for that feature in the coming weeks..

On to the weather:

The look and feel of October this weekend - a couple of cold fronts are being pushed southward across New England by an expansive area of cool high pressure dropping south from Central Canada. Each front represents a downward trend in temperatures and dew points. One moved through Thursday producing some downpours Wednesday night and Thursday morning, and a second is moving across the region Friday, kicking up winds and bringing a line of clouds and sprinkles to New England. While the air Thursday afternoon was relatively mild behind front number 1, the air behind front number 2 is noticeably cooler. Readings today across the Upper, Middle and Lower Great Lakes are in the 40s and 50s and its this air that will pour into New England for the weekend. So despite a fair amount of sunshine both Saturday and Sunday, highs will probably struggle to climb much above 60F each afternoon. Nighttime readings will be chilly as well, with temperatures dipping into the 40s across most of the area Friday, Saturday and Sunday nights. Of course, those areas that typically see the wind continue off the water through the night will hold several degrees milder.

A very cool day Monday? - While the weather pattern that we are moving into for the next 5 days or so is a quiet one overall, there will be one weather system to track that could play a fairly big role in the early week temperature forecast. When a cool dry air mass is firmly entrenched, any addition of clouds and moisture can result in a very chilly day relative to what the air mass might otherwise give us. That's exactly what we will be watching for to start the work week. A piece of energy passing across Southern New England during the day on Monday should be *just* strong enough and far enough north to produce a veil of clouds and areas of at least broken light rain showers or sprinkles. As the advancing moisture encounters the relatively dry air mass in place, evaporative cooling would be the natural result. So, if clouds and precipitation move in early in the day, temperatures are likely to go nowhere fast. With dew points in the 40s, a north wind and morning temperatures in the 40s, a lack of sun and the addition of clouds and showers would spell a raw, nasty day. So whether it actually rains or not (though at this time some light showers or sprinkles do appear likely) it could be a very chilly day with temperatures holding in the low to mid 50s!

Quiet Pattern For Now...

9/17: Another *very* long stretch between posts to this portion of the site. More regular updates will resume beginning in October. A few issues to cover:

1) The Current Weather Situation: The country as a whole has settled into a much quieter weather pattern this week. After numerous active frontal boundaries and several landfalling tropical cyclones during the last week of August and the first two weeks of September, things have settled down considerably both in the tropics (more below on this) and across the nation. Two large domes of high pressure, one extending from the western US into the central plains, and another building down into the Northeastern US from Canada are providing lots of sinking air and thus dry weather for a large chunk of the nation. The strongest jet stream is well north in Canada and the only (semi-)organized storm system near the US is a stalled out frontal boundary along the Mid-Atlantic and Southeast coasts.

Here on Cape Cod, dry and cool weather has resumed after a warm and windy Monday. Unfortunately, clouds have really been hanging on during the daylight hours, much more so than I expected either afternoon. While it is very dry above 700 mb (about 10K feet up) and high pressure is in control, there's a good deal of moisture trapped at around the 850 mb level (about 5K feet up) and there's a bit of a temperature inversion present on the morning sounding from Chatham at that same height. That, combined with a lowering sun angle and very light winds in the lowest 5000 feet of the atmosphere is making it tough to break up the deck of clouds. Thankfully, a frontal boundary dropping southward from Canada should finally mix out these clouds tonight.

Behind this front, drier and even cooler air will sink southward into the area on Thursday and Friday as a chilly dome of high pressure pushes southward into the Northeast to close out the work week. Highs Thursday will be in the 60s, with temperatures dropping into the 40s (low 50s Outer Cape) Thursday night and probably having a tough time exceeding 60F on Friday. In addition, a decent pressure gradient will set up between the surface high to our north and weak low pressure well to the south, causing a gusty northeast wind to develop both Thursday and Friday, particularly along north and east facing parts of the Cape.  

Looking out over the course of the next 5 to 7 days this general weather pattern will continue here in the Northeast, as a series of strong, but moisture-starved cold fronts drop down from Canada and push dry air into the region with sprawling high pressure centers maintaining control of the weather. In fact, over most of the country no major storminess is evident on the mid to long range charts as high pressure remains entrenched. This pattern should begin to erode during the second half of next week. Until then, it's quiet as things stand right now.

2) Meteorological Fall (Sep/Oct/Nov) is here: While the Fall Equinox is just a few days away (marking the official start to Autumn), in the world of weather, fall is really defined as the 3 month period of Sep 1 to Nov 30. This is a fascinating time of year from a meteorological perspective as the atmosphere is undergoing dramatic changes based on latitude and sunlight. The sun is sinking southward, with the declination point soon to pass south of the equator. As such, the northern latitudes of the Northern Hemisphere are losing the battle of incoming vs. outgoing radiation and are quickly beginning to cool off. Consequently, the jet stream begins to drop southward with time and the air masses moving down from the north grow cooler and cooler by the week. This is reflected well in the average monthly temperatures on the Cape. Consider that the average high on September 30th is 66F at Hyannis and that by the end of November, just 60 days from that date, that number stands at a chilly 47F. In addition, the sunsets change most rapidly this time of year. We are currently losing about 11 to 12 minutes a week! It's particularly noticeable on cloudy days, when dusk seems to approach awfully early these days...winter is coming...

3) The Tropics: Things have gone quiet for the time being. Fay, Gustav, Hanna, Ike and Josephine have essentially exhausted the energy in the tropics for now and left a relative calm (or complete atmospheric chaos depending on the perspective) in their wake(s). There's a pronounced trough extending from the Western Atlantic down into the central and eastern Caribbean, which is unfavorable for development in that region as strong upper level westerly winds are ripping apart tropical waves trying to push westward. Conditions, from a shear standpoint, become more conducive east of about 50W, however, there's an abundance of dry air from there all the way to the coast of Africa which is entirely unfavorable for development. Suffice to say, unless something develops very close to the coast of the US (not too likely right now), nothing will be forming in this pattern.

However, things could change in another 7 to 10 days, when the pattern reverts back to a more favorable one once more. The tropics may re-energize and become active for one more strong push of activity the last few days of September into the first half of October or so. To reach NOAA's official hurricane forecast, we still need at least four more named storms (not that that dictates anything) as we've had 10 and the official forecast calls for 14 to 18. In terms of available energy, aside from some areas of cooler water that were stirred up in the Gulf and near the Bahamas from Gustav, Hanna and Ike, the waters of the tropical and subtropical Atlantic remain near to slightly above normal temperature-wise (some pockets of 31C water) and still support formidable systems. Looking at some computer guidance, we see the GFS, UKMET and CMC all show a system in the far eastern Atlantic in about 6 to 7 days - this could be the start of the final push of the Cape Verde season, before development becomes confined to the Gulf, the Bahamas and the Caribbean later in October and especially into November. So while things are silent for now, the season is certainly not over.