Category: General Weather

Heat wave conditions are likely to build through the far West during the coming days while temperatures more in keeping with early fall settle into the mid-South region. This pattern will be brought about by a strong western ridge and a central U.S. trough. A strong ridge near the West Coast of the U.S. will allow heat to build northward into the Pacific Northwest and southwest Canada. At the same time an anomalously deep trough for mid summer will allow for summer polar air to drain southward from central Canada into the Plains and even the Deep South. The upper air jet stream flow forecast depicted for this coming Friday shows much more amplification than what is normal for this time of year.

The accompanying 6-10 day forecast provided by the Climate Prediction Center takes on a look more in keeping for a season other than summer. A wide portion of the central and southern U.S. are forecast to see temperatures below normal if not well below normal. Normal high temperatures for many of these areas are in the low and mid 90s at this time of year but the refreshing push of polar air from southern Canada will keep temperatures in the 80s along with lower levels of humidity. In some cases temperatures may average as much as 10 to 15 degrees below normal for a few days during the first week of August through parts of the mid Mississippi and Tennessee Valleys. On the flip side, temperatures from California northward to Washington State are expected to average from 10-15 degrees above normal during this time with widespread coverage of triple digit high temperatures. This pattern will be prime for development of seasonal wildfires throughout the West some of which may be sparked by high based thunderstorms across the mountains.

As we have seen earlier in this warm season the weather pattern is probably going to undergo changes after a few days of western heat and eastern chill. The summer weather pattern has been mostly transitional across the nation to date with most areas not getting stuck in any one extreme for very long. The forecast on the left side of the chart below is valid for August 16, 2017 and shows a reversal in the weather pattern. The spaghetti plot on the right side shows that most members are in agreement that the western ridge will be replaced by a trough while the idea of a ridge across the southern Plains to the Southeast appears to be most plausible. Assuming this forecast is in the ballpark we can expect western heat to diminish by mid August while heat and humidity return to the central and southeastern U.S.

As spring turns into summer there are mixed signals as to what summer 2017 may bring to the U.S. with respect to temperature and precipitation.  Summer for this post is defined as the months of June, July, and August (meteorological summer).

El Nino-Southern Oscillation (ENSO) during the spring season has been categorized as neutral, but forecasts for the summer are for a weak El Nino to begin to evolve. Typically during an El Nino we find temperatures near or a little cooler than normal along with somewhat wetter than normal conditions from the Plains to the East Coast during meteorological summer. To date we are still in neutral ENSO conditions. There is normally a lag time of 60 days or so for the sensible weather to catch up to the ENSO signature. We would not expect a major impact on the summer forecast from ENSO although there may be some contribution, especially since we are currently seeing a weather pattern reflective of El Nino. The chart below from the International Research Institute for Climate and Society (IRI) and the Climate Prediction Center (CPC) shows the most recent forecast for ENSO into next winter. The mean forecast (yellow line) remains under 1.0 which is the classification of El Nino but some models do forecast values over 1.0 later this summer and through the fall.

Sea surface temperature anomalies through the tropical Pacific west of South America are a little above normal but not in the classic looking El Nino signature just yet. The sea surface temperature anomalies have increased a bit during recent weeks along the Equator and indicate that the early stages of a weak El Nino could be taking place.

Another indicator we can look at is the Madden-Julian Oscillation or the MJO. The MJO is best described as areas of concentrated thunderstorms through the global tropics that propagate eastward in a 30 to 60 day cycle. These areas of moving thunderstorms influence the weather in the mid latitudes. The MJO forecast through the middle of June implies that the mostly cool, wet pattern we’ve seen during May could continue for the eastern half of the U.S. for at least the next couple of weeks.

Lastly, despite the start of meteorological summer we continue to see signs of high latitude blocking in a fashion to favor episodes of cool, sometimes wet weather for the East. Wet weather may continue to produce flooding and severe weather from the Southern Plains through the Deep South through at least mid June.

We’ve outlined three indicators that could keep the eastern half of the nation a little cooler and wetter than normal for at least part of the summer. NOAA’s forecast for official summer, (June, July, August) shows a different scenario with warmth for the South and East while cooler and wet conditions cover the interior mountains of the West. It should be noted that some of the most recent modeled forecasts for June produced by NOAA at the end of May do depict cooler than average temperatures for a majority of the nation, including the East and South.

Sea surface temperatures across the western Atlantic and more so through the tropical Atlantic are milder than average as we approach summer’s start. This type of pattern could help elevate temperatures across the eastern and southern U.S. once high latitude blocking and the effects from MJO diminish later in June. It’s possible that the NOAA forecast could have validity to it if one is patient and allows the leftover spring pattern to weaken and fade. Could this be a summer like 1988 which started slow but ended with widespread heat? The South and Plains may be slower to warm with excess soil moisture levels in place but that could add humidity to the equation making for more uncomfortable conditions. There are certainly differing signals for the summer outlook at this time but most of the signs for cooler readings are short term. Once we reach late June and beyond the warmer scenario of NOAA is plausible if El Nino is slow to start and remains weak.

It’s been a very wet spring across much of the Northeast, and it’s going to get a lot wetter over the next few days.

After experiencing drought conditions for much of the past year, a much wetter pattern has settled in across the Northeast this Spring. Much of the region has received 6-12 inches of rain since the middle of March, which is up to twice the normal amount. As a result, flooding has been observed, especially north of the border into portions of Ontario and Quebec. Persistent heavy rains across these provinces has flooded hundreds of communities in the past few weeks.

Instead of relief, it looks like conditions will worsen this weekend. Low pressure will move into the Carolinas on Friday, then off the East Coast on Saturday, slowly moving northeastward over the weekend. Rain and thunderstorms will move across the Mid-Atlantic states on Friday, spreading northeastward during the day.  The rain should reach the New York City area around daybreak Saturday, moving into Southern New England during the afternoon. As the system slows down south of Long Island, heavy rain is likely across portions of the Northeast Saturday night into Sunday. Although the rain will taper off Sunday afternoon, it may not completely end until sometime on Monday as the storm takes it time to depart the region.

While heavy rain and flooding are the main threats with this system, they are not the only threats. As the system intensifies over the North Atlantic, gusty winds are expected, especially along the coastline of New England and Long Island. Sustained winds of 20-30 mph with gusts to 50 mph are likely. These winds will help churn up some rough seas, which may lead to some coastal flooding on Sunday, especially along east-facing shorelines in New England.

Much of the last week to 10 days has been characterized by cool and damp conditions across the Northeast, thanks to an upper-level low pressure area that has been anchored in placed. That pattern is finally changing, and the result will be welcome news across the region. A ridge of high pressure will build in for much of the upcoming week, which means the clouds and below normal temperatures will be replaced by sunshine and near to above normal temperatures.

High temperatures across the Northeast have only been in the 50s and 60s for the past several days across much of the region, which is 5 to 10 degrees below normal. By mid-week, temperatures should reach the 70s and 80s across much of the region, which will be 5 to 10 degrees (or more) above normal.