Winter Forecast 2013-14: Mild With An Occasional Chilly Ride

This is our eighth winter forecast here at Phillyweather.net -- we've produced a mixed bag of wintry results over the years -- some of them solid, others not-so-much. With the exception of temperatures in 2011-12, we've been pretty close to the mark in terms of getting that aspect of the forecast right. Snow is another story -- and we will say it time and again that snow is a wildcard on a seasonal basis.  Even "good" setups don't always produce.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrXgb0rNhBMn6Llb6stK3pQPOfxQqFvFVAEr3F9KF2kMMiGBa4p-48HyzEArVlm5UvnW7S9JSkGQiitanue1KC1I5-4BYumNHySpbu6mFuPP7XnrvGqMBHP0cm2ZjsCo5IeV3qoX-mRMjE/s1600/WINTERHISTORY.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrXgb0rNhBMn6Llb6stK3pQPOfxQqFvFVAEr3F9KF2kMMiGBa4p-48HyzEArVlm5UvnW7S9JSkGQiitanue1KC1I5-4BYumNHySpbu6mFuPP7XnrvGqMBHP0cm2ZjsCo5IeV3qoX-mRMjE/s400/WINTERHISTORY.jpg" width="400" /></a></div><br />We've seen a general tendency for a more amplified pattern take over from September on and we feel that we will see that continue through the winter. Amplified does not necessary result in a cold and snow scenario for us but we will likely see periods of warmth followed by periods of cool, rinse and repeat.  Without the influence of blocky weather (NAO, AO) setting up shop, cold may be more fleeting than entrenched. It is winter -- it will get cold -- but the magnitude of chill this winter may not be on the order of what we dealt with in late January into February last year.<br /><br />Most of the indicators out there lean warm -- even if a Nino does develop, it may not develop in time to "save" winter for the snow starved nor set up in a position ideal to help influence a colder pattern for the eastern half of the United States.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW2IYU6ijAia4o-ebgbTl9GqIaLbOJA-07zqDpVDnC3NWQUeVAmVYnxdFX8Yxwb5D4EEbcipaDH6egfCqjhpf4N5wl764ICDL_AIMOhIzYPoKHN38EuvLV-NRS55lyShJ9zEQBFUSSkPJ7/s1600/WINTERFOR1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW2IYU6ijAia4o-ebgbTl9GqIaLbOJA-07zqDpVDnC3NWQUeVAmVYnxdFX8Yxwb5D4EEbcipaDH6egfCqjhpf4N5wl764ICDL_AIMOhIzYPoKHN38EuvLV-NRS55lyShJ9zEQBFUSSkPJ7/s400/WINTERFOR1.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"></div>The best comparison winters out there -- from a Nino/Nina/neutral standpoint, to October temperatures, combined with similar Arctic Oscillation tendencies -- are last winter and 2001-2002. Neither of them were good from a snow or cold standpoint. It doesn't mean we won't be cold at all during winter -- I think the amplified pattern in place allows for *some* colder periods that last longer than others (the holidays into early January is our best guess for when that takes place).<br /><br />On the whole, we think it will be a milder winter...on the order of at least a degree, perhaps a degree and a half above average (36.3-36.8 degree range, average is 35.3). Warmest periods to average are probably the first three weeks of December and the last two weeks of February.<br /><br />In terms of snowfall, we lean below average (21.8" is average) with our projection of 14 to 19 inches for Philadelphia. Most of the region should see slightly below average snowfall, with the Poconos closest overall to average as they get into the lower 50's on snowfall. The best time frame for snow looks to be in the middle and latter portions of January, a little earlier than our historical "peak" for snow. This would time roughly with us getting out of our colder look that sets up near the holidays.<br /><br />Snowfall in Philadelphia a wildcard, as usual, so snowfall seasonal predictions should be taken with larger grains of salt than temperature predictions.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXVy_eNyZQmmA04lYslwDWmu7uHk8PTuAf6F7mPD6sA_KtCt4-d4VrgC295DQYpX9axwD2CGRE_iKp_32sspCZSQZxqmCRU2s9ojOIGz2SGgSOg3UbwBkRwO6c2lsBNbRKHWRwwjmZEB-/s1600/WINTERFOR2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXVy_eNyZQmmA04lYslwDWmu7uHk8PTuAf6F7mPD6sA_KtCt4-d4VrgC295DQYpX9axwD2CGRE_iKp_32sspCZSQZxqmCRU2s9ojOIGz2SGgSOg3UbwBkRwO6c2lsBNbRKHWRwwjmZEB-/s400/WINTERFOR2.jpg" width="400" /></a></div><br />That said, warmer years do usually correlate to less snow (there are exceptions, of course!). Given the odds of a relatively milder winter, the "safe" play is to go with less snow than average based on the odds.<br /><br />With that said, if we do get ten inches of snow, it would be more than last winter. Twelve gets us more than the last two winters combined.  Philadelphia hasn't gone three winters with less than ten inches of snow since the early 1930's. Historically, such odds are tough to pull off...but are worth noting here in case we end up in a rarefied spot for winter.

long range forecasting Winter 2013-2014 winter forecast winter forecast history Winter Forecast 2013-14: Mild With An Occasional Chilly Ride

This is our eighth winter forecast here at Phillyweather.net -- we've produced a mixed bag of wintry results over the years -- some of t...

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Winter Forecast 2013-14 -- The Players On The Field

The cooler end to October, at least compared to what we experienced in the first two plus weeks of the month, have some of us pining for winter to set in full time, permanently. With that, the thought of what may, possibly, could, ultimately happen this winter is on some of your minds.<br /><div><br /></div><div>As is usual tradition, our winter outlook tries to get to the bottom of the plethora of mysteries out there and comes up with a quantifiable expectation for what *may* transpire in the upcoming winter.  Philadelphia's position in the transition zone between the milder influences of the Gulf Stream and the colder northern climes makes forecasting winter more "fun" and not necessarily one of higher confidence here compared to in Boston or in Minneapolis.<br /><br />This winter outlook highlights the usual players that make up the winter and what those typically suggest when factored together in an upcoming winter.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikABFZTFScP9fF3dWBuSoWevivkV-p9Twf9OIOvppIjpusqxpxQYqJc_5ZXaAcb50RxaTEe93ctdhyphenhyphenxkblMNqIygc6ZiSckYkJ3cOnZC13EnRWO40oBdiRRIHKIuuyWaYJ25qFnVUDICO5/s1600/WINTERNAO.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikABFZTFScP9fF3dWBuSoWevivkV-p9Twf9OIOvppIjpusqxpxQYqJc_5ZXaAcb50RxaTEe93ctdhyphenhyphenxkblMNqIygc6ZiSckYkJ3cOnZC13EnRWO40oBdiRRIHKIuuyWaYJ25qFnVUDICO5/s400/WINTERNAO.jpg" width="400" /></a></div><br /><br /><b>First, the North Atlantic Oscillation (NAO):</b>  NAO is reflective of the state of blocking in the atmosphere based on pressure setups in the North Atlantic. Our cold season last year featured very impressive blocking in October, November, and in late February into March but largely was neutral to positive for the heart of cold season. This was reflected in the reality that winter temperatures ended up above average last year despite a colder than average November, February, and March (-NAO's typically yield colder conditions in winter).  The NAO in October, historically, has a 60% tendency to have an opposite state for the winter overall (if the NAO is positive in October, it would be negative in the following winter six out of ten years). It's a decent, not great correlation. Based on where we're working towards this winter, the NAO should average out to negative for the month overall. Note the rather amplified pattern we've seen of late -- this typically is a sign of what may, at times, be a blocky regime through the course of winter. However, it may not necessarily be often enough to bring lasting cold through the heart of winter.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9SviKpb7pwRiNgZ43m3euagN703-0UPXtZ0Kl_vLLV5cCWnrQ7cKyR0KQDCbFyJzYkgSma2XYVDt2YxjbQ29kiWQMXpesh2gzFeZhpDTeHyv1lKrTM1r-vLpLtThLWwWyv5yFA69uhrQH/s1600/WINTERAO.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9SviKpb7pwRiNgZ43m3euagN703-0UPXtZ0Kl_vLLV5cCWnrQ7cKyR0KQDCbFyJzYkgSma2XYVDt2YxjbQ29kiWQMXpesh2gzFeZhpDTeHyv1lKrTM1r-vLpLtThLWwWyv5yFA69uhrQH/s400/WINTERAO.jpg" width="400" /></a></div><br /><b>Second, the Arctic Oscillation (AO):</b> The AO and NAO work in sync rather frequently (45 of the last 64 winters feature AO/NAO agreement). Last winter featured one of the exceptions to that pattern -- we had a rather negative AO regime through the course of the winter but the NAO did not respond in kind.  An unfavorable NAO, combined with an unfavorable Pacific pattern, dumped the bulk of chill into Alaska last winter as opposed to down into the Northeast. There is a lower statistical correlation between October's AO and the proceeding winter AO (55% of agreement) than there is between the summer AO and the proceeding winter (60% agreement). This summer's AO registered positive, while October for the whole will likely register positive as well.  Positive AO status often yields milder conditions for us.<br /><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSYbf3XQmnCw1OXXGBC-4nYead5HapmEgeyw1Lh8x9nbi8Y80dheGeI5WhkGhX6zElusEYpEn4QnYK_fj0vdKNTxsDaZkdwt6qHvUDXH-fabmZGUzVtLOJxWcCDNHWEJwJG6S5DOSKmHXt/s1600/WINTERMEI.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="217" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSYbf3XQmnCw1OXXGBC-4nYead5HapmEgeyw1Lh8x9nbi8Y80dheGeI5WhkGhX6zElusEYpEn4QnYK_fj0vdKNTxsDaZkdwt6qHvUDXH-fabmZGUzVtLOJxWcCDNHWEJwJG6S5DOSKmHXt/s400/WINTERMEI.jpg" width="400" /></a></div><br /><b>El Nino/La Nina/La Nada:</b>  The tropical Pacific does provide some steering and "big picture" for the following winter. The current neutral or "nada" look in the tropical Pacific is one that modeling suggests maintain for a chunk of the winter. We could drift into a warmer look in the Pacific late in the winter but it may not be in time to provide the corresponding atmospheric result that the warmer Pacific would provide.  More important, the part of the Pacific that is warming (near South America) isn't the part you ideally want if you are a fan of cold and snow (east Ninos tend to <a href="http://philadelphiaweather.blogspot.com/2009/07/thoughts-on-nino-and-winter.html" target="_blank">produce warmer results for us than West</a>). Neutral winters of late include last winter, 2003-2004, and 1996-1997. Two of those three ended up warm, with 03-04 the exception from a temperature standpoint thanks to strong arctic blocking.<br /><br /><b>October's temperatures:</b> <a href="http://philadelphiaweather.blogspot.com/2013/10/do-october-temperatures-matter-for.html" target="_blank">There's a relatively strong correlation between October temperature</a> and winter temperature over a long term period of time. The colder or warmer it is in October, the stronger the tendency it is for the following winter to follow suit. This October will end up above average on temperatures and in the warmer third of temperatures since 1940, which has a stronger than 70 percent correlation to above average temperatures in the proceeding winter.<br /><br />So...all of that put together...what happens this winter? We will lay that out this evening.</div>

long range forecasting winter forecast discussion winter forecasts Winter Forecast 2013-14 -- The Players On The Field

The cooler end to October, at least compared to what we experienced in the first two plus weeks of the month, have some of us pining for win...

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