12:40 PM | Tropical Storm Chantal heads for the Caribbean

Discussion

It has been quiet in the Atlantic Basin since mid-June with respect to tropical systems, but now Chantal has reached tropical storm status and is churning towards the Caribbean Sea at a pretty good clip. Chantal developed from a strong easterly wave that slipped off the African west coast a few days ago in what is likely to be a pattern that is frequently repeated over the next few months. The 11AM readings on Chantal have sustained winds at 45 mph with gusts to 60 and rapid movement to the west-northwest at 25 mph. An index that we track here at thesiweather.com called the Madden-Julian Oscillation (MJO) is quite supportive of an active period into at least mid-July as the index will remain in territory (i.e., phases 2 and 3) that favor Atlantic Basin tropical activity. The MJO is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days.

All indications suggest Chantal will reach the Caribbean Sea within the next 36 hours and then approach the island of Hispaniola later this week. A track over this island would likely, at least temporarily, prevent or slow down intensification of Chantal as mountain peaks tend to interrupt the low-level circulation flow (10,000 foot peaks in Dominican Republic). By the weekend, Chantal could very well be in the vicinity of the Bahamas and, ultimately, it could have an effect on the Southeast US.

7:00 AM | The return of the daily threat for showers and thunderstorms

6-Day Forecast

Today

Partly sunny, hot, humid, showers and thunderstorms possible, highs near 90

Tonight

Mostly cloudy skies, muggy, mild, lows near 70 degrees

Tuesday

Partly sunny, very warm, humid, chance for showers and thunderstorms, upper 80’s

Tuesday Night

Evening showers and thunderstorms possible, muggy, mild, lows in the low 70’s

Wednesday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Thursday

Partly sunny, hot, humid, showers and thunderstorms likely, mid 80’s

Friday

Partly sunny, warm, humid, chance for a shower or thunderstorm, mid 80’s

Saturday

Partly sunny, warm, humid, chance for a shower or thunderstorm, low 80’s

Discussion

High pressure off the east coast will continue to pump the area with tropical air and the threat for an occasional shower and thunderstorm. High temperatures will remain on the high side during the first half of the week, but will trend downward after that.

7:00 AM | Rather typical hot and humid summertime weather conditions

6-Day Forecast

Today

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, highs near 90 degrees

Tonight

Partly cloudy, muggy, mild, lows near 70 degrees

Saturday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Saturday Night

Partly cloudy, muggy, mild, slight chance for a shower or thunderstorm, lows in the low 70’s

Sunday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Monday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Tuesday

Mostly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Wednesday

Mostly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Discussion

High pressure off the east coast has expanded westward and it will provide us with generally hot and humid weather over the next few days along with a slight chance for an occasional shower or thunderstorm. Highs will reach or slightly surpass 90 degrees each day and humidity will stay at rather uncomfortable levels.

7:00 AM | More sun, higher temperatures, less chance for rain as east coast high pressure builds westward

6-Day Forecast

Today

Partly sunny, hot, humid, chance for a shower or thunderstorm, highs near 90 degrees

Tonight

Partly cloudy, muggy, mild, lows in the low 70’s

Friday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Friday Night

Partly cloudy, muggy, mild, lows in the low 70’s

Saturday

Partly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Sunday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Monday

Mostly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Tuesday

Mostly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Discussion

High pressure off the east coast has expanded westward and effectively cut off the flow of air that has been riding up the east coast in recent days from the Gulf of Mexico. As a result, the pattern that we had earlier this week has evolved into one with only widely scattered showers and thunderstorms. Temperatures will climb to or slightly above 90 degrees over the next several days and humidity levels will remain on the high side.

11:45 AM | An update on solar cycle 24 and a newly emerged active sunspot region

Discussion

We are currently over four years into Solar Cycle 24 and it continues to “underwhelm” and be on a pace that would make it the smallest sunspot cycle since Cycle 14 which peaked in February 1906. There is, however, an active sunspot region that is now rotating to a position that will face the Earth directly in just a few days. In fact, this sunspot region, officially named AR1785, generated an M-class solar flare earlier today, but that should not have an effect on the Earth’s upper atmosphere as it occurred while it was not directly facing the Earth.

Despite this newly emerged active sunspot region, solar activity in general has been rather low this year and this is despite the fact that this particular cycle is approaching the expected solar maximum time period in the middle or latter part of 2013. There is a growing belief that, based on the lack of any substantial spike in sunspot activity, the peak of this cycle may have already happened during the latter part of 2011 - much earlier than originally forecasted. Another theory suggests that there may be a “double-peak” solar maximum for this cycle which would mean there could be a sharp spike in sunspot activity still to come later later this year or in early 2014.

Cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009 which included more spotless days on the sun compared to any minimum in almost a century. While a weaker solar cycle does not rule out the threat for strong solar storms, it does suggest that they will occur less often than during the stronger and more active cycles. The increasingly likely outcome for a weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago with solar cycle 22. In addition, there are some solar scientists who are already predicting that the next cycle, 25, will be even weaker than the current one. According to some research studies, weak solar cycles with extended lengths may actually have a downward effect on global temperatures in the medium and longer range. Weak solar cycles tend to last longer than the strong ones. There have been historical periods with minimal sunspot activity that lasted for several decades such as from the mid 1600’s to the early 1700’s when the so-called “Maunder Minimum” occurred and this period was quite cold globally.

Another interesting aspect to these solar cycle predictions is that this apparent long-term period of weaker and extended solar cycles looks like it will coincide with a cold phase of the Pacific Ocean (negative Pacific Decadal Oscillation (PDO) index). The Pacific Ocean slipped into a cold phase a few years ago and these longer-term oceanic phases tend to last for two or three decades. Global temperature anomalies have tended to trend downward over the past few years seemingly right after the PDO flipped to a negative (cold) phase. We’ll continue to periodically report on sunspot activity and the oceanic cycles here at “thesiweather.com” and monitor any important changes that may unfold.

Video

httpv://youtu.be/YSCtQecALL8

7:00 AM | Expanding east coast high pressure will bring about increasing temperatures and decreasing rainfall by the end of the week

6-Day Forecast

Today

Mostly cloudy, warm, humid, scattered showers and thunderstorms, highs in the low-to-mid 80’s

Tonight

Evening showers and thunderstorms possible; otherwise, mostly cloudy skies, muggy, mild, lows near 70 degrees

Thursday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Thursday Night

Partly cloudy, muggy, mild, lows in the low 70’s

Friday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Saturday

Partly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Sunday

Mostly sunny, hot, humid, slight chance for a shower or thunderstorm, near 90

Monday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Discussion

High pressure off the east coast will expand westward over the next few days and this will have two effects on the region: 1) an increase in temperatures and 2) a decrease in the rainfall activity. As the high expands inland from off of the east coast, the persistent southerly flow of tropical air along the east coast will finally diminish and this will reduce the numerous showers and thunderstorms of recent days to a widely scattered variety. Temperatures will climb to near or just above 90 degrees late this week and during the weekend as well.

3:00 PM | A "wall-of-water" now riding up the east coast

Discussion

A widespread area of showers and thunderstorms that currently extends from the DC metro region all the way down to Georgia is riding right up the east coast. A strong southerly flow of air sandwiched between high pressure off the east coast and an inland upper level low pressure trough is pumping tropical moisture right up the eastern seaboard from the Gulf of Mexico. This “wall of water” will hit the DC region shortly with showers and embedded thunderstorms and some of the rain will be heavy at times, and the threat for rain will last for a few hours. The Philly metro region should be affected by this impressive batch of rainfall during the evening hours with the heaviest rain likely on the eastern side I-95. New York City and New England will get their turn with this area of rain later tonight. Flash flooding will no doubt be a significant concern in many Mid-Atlantic locations over the next several hours given the already well-saturated grounds and the additional heavy rainfall that will fall.

3:00 PM | A "wall-of-water" now riding up the east coast

Discussion

A widespread area of showers and thunderstorms that currently extends from the DC metro region all the way down to Georgia is riding right up the east coast. A strong southerly flow of air sandwiched between high pressure off the east coast and an inland upper level low pressure trough is pumping tropical moisture right up the eastern seaboard from the Gulf of Mexico. This “wall of water” will hit the DC region shortly with showers and embedded thunderstorms and some of the rain will be heavy at times, and the threat for rain will last for a few hours. The Philly metro region should be affected by this impressive batch of rainfall during the evening hours with the heaviest rain likely on the western side I-95. New York City and New England will get their turn with this area of rain later tonight. Flash flooding will no doubt be a significant concern in many Mid-Atlantic locations over the next several hours given the already well-saturated grounds and the additional heavy rainfall that will fall.

7:00 AM | Another day with tropical moisture and the threat for more showers and thunderstorms

6-Day Forecast

Today

Mostly cloudy, warm, humid, showers and thunderstorms likely, highs in the low 80’s

Tonight

Evening showers and thunderstorms possible; otherwise, mostly cloudy skies, muggy, mild, lows near 70 degrees

Wednesday

Mostly cloudy, warm, humid, showers and thunderstorms possible, mid 80’s

Wednesday Night

Evening showers and thunderstorms possible, muggy, mild, lows near 70

Thursday

Partly sunny, very warm, humid, chance for showers and thunderstorms, upper 80’s

Friday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Saturday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Sunday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Discussion

High pressure off the east coast will continue to pump the region with tropical air from the Gulf of Mexico; consequently, the threat for showers and thunderstorms will continue and so will the possibility of localized flash flooding. As the week progresses, however, that Bermuda high pressure system will retrograde back towards the coast and this movement will have the effect of decreasing chances for rain around here and increasing the temperatures. Highs by late in the week will reach or slightly surpass 90 degrees and the relatively hot and humid weather will continue this weekend and while there still can be some shower and thunderstorm activity, they will be far less numerous compared to what we have been experiencing.

Video

httpv://youtu.be/GAvW1m61Lqw

7:00 AM | Wet pattern continues as southerly flow along the coast brings tropical moisture from the Gulf of Mexico

6-Day Forecast

Today

Mostly cloudy, warm, humid, occasional showers and thunderstorms, some of the rain will be heavy and any storm can reach strong-to-severe levels, highs in the low 80’s

Tonight

Evening showers and thunderstorms likely, some of the rain will be heavy and any storm can reach strong-to-severe levels; otherwise, mostly cloudy skies, muggy, mild, lows in the upper 60’s

Tuesday

Mostly cloudy, warm, humid, showers and thunderstorms likely, some of the rain will be heavy and any storm can reach strong-to-severe levels, mid 80’s

Tuesday Night

Evening showers and thunderstorms likely, some of the rain will be heavy and any storm can reach strong-to-severe levels; otherwise, mostly cloudy skies, muggy, mild, lows in the upper 60’s

Wednesday

Mostly cloudy, warm, humid, showers and thunderstorms possible, mid 80’s

Thursday

Partly sunny, very warm, humid, chance of showers and thunderstorms possible, mid-to-upper 80’s

Friday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Saturday

Partly sunny, hot, humid, chance for a shower or thunderstorm, near 90

Discussion

It turned out to be the wettest June ever recorded in some Mid-Atlantic locations (e.g., Philly, Wilmington, DE) and July is starting out on a very wet note as well. Philly Int'l Airport ended up with a record 10.56 inches of rain for the month of June and it was their sixth wettest month ever. Torrential rain has already occurred this morning in many Mid-Atlantic locations and more is on the way, but there are signs that this very wet pattern will evolve into a primarily hot pattern by the end of the week, and the threat for rain will gradually diminish as the week progresses.

The combination of a strong upper level low pressure system over the Ohio Valley and an extensive surface high pressure system off the east coast will keep a moist southerly flow of air in place along the east coast for the next couple of days. This type of wind flow will bring copious amounts of tropical moisture up the east coast from the Gulf of Mexico and the result will be more torrential rainfall right into mid-week. By later this week, however, the showers and thunderstorms will become more and more widely scattered and the main weather story will likely be the developing heat as high temperatures should climb to 90 degrees or above.

Video

httpv://youtu.be/HgQXoU5HwTk