Heavy rain, high surf on deck with storms looming

Steven Gibbons/The OregonianSwells up to 20-feet will make for good surf watching along the Oregon Coast this week, like in this photograph from Heceta Head in January 2007.

Ready, set, soak.

A potent storm packing tropical moisture will aim a Pacific fire hose at the Northwest starting early tomorrow morning and lasting until Wednesday night, forecasters said today.

Although the system -- which is being carried along by a 200-mph jet stream -- will dump a half foot of snow in the Cascades, snow levels will soar to 7,000 to 8,000 feet by late tomorrow afternoon, changing that snow to rain.

The blast of Pacific rain could cause rivers and streams to quickly rise, especially on the Northern Oregon and Southwest Washington coasts, said Chris Collins, a forecaster for the National Weather Service in Portland.

National Weather ServiceTuesday's rainfall forecast.

National Weather ServiceWednesday's rainfall forecast

National Weather ServiceThursday's rainfall forecast

"I wouldn't be surprised to see five to eight inches of rain fall on the coastal mountains,'' Collins said. "Some places could see ten inches of rain."

Heavy rain could lead to minor tidal flooding on coastal rivers such as the Nehalem, Wilson and Trask thanks to the highest tides of the month and building seas, with swells of 16 to 18 feet on Wednesday and Thursday mornings. Tidal flooding could also occur on Willapa Bay in Southwest Washington as high tides near 11 feet.

Waves and strong ebb currents will also create 20 to 22 foot seas at the Columbia River bar, leading to very rough conditions. Strong rip currents are also likely along the coast, where winds will gust to 55 to 60 mph tomorrow and Wednesday.

At 1:40 p.m. this afternoon, the weather service issued a high wind watch for the North and Central Oregon coast through tomorrow evening. Gusts to near 60 mph could rake exposed headlands and beaches, with sustained winds of 40 mph.

Urban street flooding is also a distinct possibility, forecasters said, because of storm drains choked with leaves.

Portland has had measurable rain every day this month, with 2.09 inches through noon today, about half an inch above normal. Last year at this time, rainfall was a paltry 0.22 inches.

The next wave of rain could also set off landslides and debris flows.

"Here we go again,'' said George Taylor of Applied Climate Services in Corvallis. "It looks like a pretty wet one, but these fire hose storm are really hard to predict: If you're under the fire hose, you're going to get pretty wet...but they tend to spray erratically."

GOES WEST VISIBLEA conveyor belt of moisture is set to bring heavy rain, wind and possible flooding and landslides to the Pacific Northwest.

Officials will keep a close watch on areas burned during the Gnarl Ridge fire on the Northeast flanks of Mount Hood this summer, where bare hillsides have already lead to rapid runoff and small debris flows and landslides.

Debris flow could also occur on areas burned by the Kitson fire, which burned through steeply timbered hillsides four miles Southeast of Oakridge in September.

Rain stays in the forecast into Friday, but look for a drying trend by the weekend, with partly cloudy skies and temperatures in the high 50s.

2008 was not as hot

Meteorologists with the United Kingdom's weather service say the average global temperature this past year was about 57.7°F, the coolest this decade. Cooler water temperatures in the Pacific Ocean, referred to as La Nina, kept the atmosphere a little cooler last year, they say.

But this little drop is not necessarily a sign that global warming is slowing down. "Absolutely not," said Dr. Peter Stott, from the UKMET office. "If we are going to understand climate change we need to look at long-term trends."

Even though last year was a little cooler than recent years, 2008 would still rank as the tenth hottest year on record. The hottest was 1998. The UKMET climate office uses satellite data, ground weather stations and buoys to calculate the global temperature.

Top Ten in '08

Beginning Monday December 8th, The Weather Channel will be counting down the top ten weather events of 2008. I don't personally know what the top ten are. Apparently TWC doesn't trust me with that kind of top secret info. That's OK. I present to you now Mike Bettes' Biggest Weather Events of the Year!

1. Hurricane Ike
2. Spring/Summer Midwest Floods
3. Super Tuesday Tornado Outbreak
4. Record Midwest Snow Season
5. Hurricane Gustav
6. Mother's Day Outbreak
7. Prolonged Southeast Drought
8. California Wildfires
9. Rising Water Level at Lake Powell(+23')
10. Early March Midwest Snow Storms

I'm interested to see your top ten.

Another Earthquake

According to the USGS website, there was another small earthquake Wednesday at 1:21 PM. It was located 7 miles NNW of Guy or 47 miles north of Little Rock and it was a magnitude 2.5

This one is located well away from the cluster of small earthquakes which occurred near Magnet Cove last month. Did you feel it???

In the days to come, we'll be talking more and more about an active weather pattern for the state. The general theme will be below average temperatures for quite awhile.

Tropical Atlantic springing to life

[Updates follow original entry; latest as of 4pm EDT Thursday July 3.]

A surface low pressure center -- the most organized disturbance so far this season to emerge off the coast of Africa -- is in the eastern tropical Atlantic.

On the other side of the tropical Atlantic, a little doohickey (what appeared to be a sharp tropical wave at the surface but with a circulation spinning aloft) flared up Wednesday afternoon as it approached the Windward Islands.

What the location of the current two systems tells us is that we're shifting gears from June, when most tropical cyclone development takes place in the Gulf of Mexico and western Caribbean Sea, to July, which is a transition month on the way to August, when the balance tilts to the tropical Atlantic, and the basin as a whole becomes more conducive to development.

JUNE

EARLY JULY

MID JULY

LATE JULY

EARLY AUGUST

If that eastern Atlantic low were to become a tropical storm far to the east (it remains to be seen whether that will happen), such an occurrence would be unusually early. What would that portend for the remainder of the season? The peak is still 1-3 months away, and like with any long-range seasonal outlook, there's no way of knowing exactly what will happen far in advance ... and outcomes after early flare-ups can run the gamut.

For example, things got cranking early in the season in 2005, and we all now know how that season turned out. On this date (July 3) in '05, the depression that would go on to become already the third named storm (Cindy) formed; the center of Cindy would, in an eerie foreshadowing of what happened on August 29 of that year, pass just to the east of New Orleans.

However, as early as mid-June of the following year, as I similarly blogged at the time, the tropical Atlantic was lit up (below), and, Ernesto notwithstanding, the remainder of the 2006 season overall was like night and day compared to 2005.

The 2007 hurricane season was a rough one in some other countries, but with it and the '06 season having been much less destructive in the U.S. than the ones in 2004 and 2005, I hope there's not too much complacency. Not knowing what the outcome this year will be, let's hope for the best but be prepared for the worst. (Although a trite expression, it always rings true for hurricanes!)

THURSDAY MORNING UPDATE

With the surface circulation still well-defined, and convection (rain & thunderstorms) persisting around the center, the National Hurricane Center has designated the system in the far eastern Atlantic to be a tropical depression. After brushing Cape Verde with showers and gusty winds, it is not a threat to land for the foreseeable future. If T.D. #2 strengthens and becomes a tropical storm, it would get the name "Bertha."

Bertha was also the name of a hurricane in 1996 which formed in the Atlantic (not quite as far east) in early July, in fact its incipient circulation was first detected on satellite imagery on July 3! Bertha would go on to survive all the way across the Atlantic and make landfall on the North Carolina coast on the 12th of July.

UPDATE 11AM EDT THURSDAY JULY 3

The depression has been upgraded to Tropical Storm Bertha.

[Click on image for large version.]

UPDATE 4PM EDT THURSDAY

Per TWC's point of origin maps, and in double-checking the NOAA track climatology viewer, Bertha has apparently become an Atlantic tropical storm much farther east than any other storm on record so early in the season.

I've updated the map from earlier in this blog for the first 1/3 of July (no June storm is close) to put a red dot where Bertha was named (below). 1996's Bertha -- represented by the easternmost yellow dot -- had been the farthest east until eclipsed by 2008's Bertha.

Caveats:

-There may have been other tropical cyclones of storm intensity as far or farther east prior to the satellite era that were not officially designated to be tropical storms.

-Even during the modern era, when to designate a cyclone to be a tropical storm is a judgment made by the National Hurricane Center with some inherent subjectivity.

The latest TWC forecast track for Bertha can be found here.

Meanwhile, in the Gulf of Mexico ...

[Sunday update on the Gulf moisture and Tropical Storm Bertha follows original entry]

While all eyes are on Tropical Storm Bertha, it's in the middle of nowhere and of no immediate threat to land, and its ultimate destination is uncertain.

However, a tropical weather situation which could be life-threatening is imminent, and it just goes to show that you don't need a hurricane or even a named tropical storm for that to be the case.

There has been a big flare-up of convection (showers and thunderstorms) in the western Gulf of Mexico today, associated with deep tropical moisture, a weak surface trough of low pressure and low-level converging winds, and upper-level "divergence."

Tropical cyclone development is not expected at this time, but the potential exists for excessive rainfall in Mexico along with flooding and flash flooding (and mudslides in the eastern portion of the more mountainous inland terrain), as the wet pattern persists for the next few days.

[Crop of image from Wikimedia Atlas of the World under the GNU Free Documentation License]

Although the most extreme rainfall will occur south of the border (and let's hope this system does not achieve its worst-case scenario there), heavy showers are already affecting parts of southernmost Texas. That could eventually result in local flash flooding, but otherwise, any rain that falls in this region would be welcome and beneficial, given the extreme drought which exists.

[Radar image source: GRLevelX]

UPDATE 1PM EDT SUNDAY JULY 6

TEXAS

Continued good news in South Texas (well, except perhaps for folks' holiday weekend outdoor plans), as the combination of tropical moisture and other atmospheric triggers continues to bring rain, which is welcome as long as too much doesn't fall too quickly, and amounts are starting to add up. A statement just issued by the National Weather Service office in Brownsville indicates that in some places upwards of 4-5" has fallen so far since July 1, and additional locally heavy showers are around today.

MEXICO

Yesterday's big thunderstorm cluster in the satellite image above (early in the original entry) has given way to deep "convection" which is more sporadic over the western Gulf, but Mexico is not yet out of the woods. There's still a big area of deep tropical moisture, and the risk of flash flooding will still exist for the next couple of days, not only on and near the country's Gulf of Mexico coast but also on the Pacific side, where Tropical Depression Five-E is skirting that coast.

BERTHA

Bertha remains a weak tropical storm way out in the Atlantic. The National Hurricane Center said in their latest advisory, "it is much too early to determine if Bertha will eventually affect any land areas." Indeed, at least as far as any direct effects are concerned. (Indirectly, ocean waves which are generated can affect areas far away from storms.)

The place first in line near the potential path would be Bermuda, but that's not for a few days, and impacts there will depend on the exact track and intensity of Bertha. Although the Leeward Islands, Turks and Caicos, and southern Bahamas need to stay apprised of the storm's progress, they're not the most likely destination.

As for farther down the line, including the mainland United States ... A few folks who posted comments to my first entry on the storm have speculated where Bertha might go, and there have been some interesting forecasts out there on the web.

Inherent uncertainty exists in any 7-day track forecast, particularly so in this case, and there's also the question of how intense (or not) the tropical cyclone will get (it's not like Bertha is presently a Category 5 hurricane). The bottom line if you're in Myrtle Beach or the Outer Banks or anywhere else on the East Coast is that the storm is of no immediate threat, it has a long row to hoe and would have a lot of hurdles to get over to make landfall in the U.S. and do so as a hurricane, and even if that were to happen there's plenty of time to monitor the situation.

Stay tuned ...

100-year flood?

As illustrated by the above graphics, there was yet another round of heavy rain and flash flooding a few days ago in the central U.S., this time in southern Michigan and in the Kansas City metro area.

Fortunately, the deluges were localized and short-lived enough to not raise river levels significantly higher; although the weather pattern is such that there could be additional clusters of heavy thunderstorms at times in the Midwest, hopefully the worst of the large-scale flooding, which started really getting out of hand exactly a month ago (June 6-8), is mercifully over.

Just how epic was it? A 100-year flood? A 500-year flood? A gazillion-year flood? And how can, for example, "100-year" floods happen again and again within a much shorter time frame?

Here are the opening sentences from this recent Associated Press article on the Midwest flooding:

"Fifteen years ago, after the Midwest was swamped with what was pronounced a "100-year" or even a "500-year" flood, some folks figured they would never again see such a disaster in their lifetime. Some even dropped their flood insurance. Big mistake."

Why is such terminology so misunderstood? There are all kinds of problems and complications with it.

First of all, there's the overall total magnitude of a flood in a region (worst flood in X years) vs. the "recurrence interval" in a particular location, such as at one's home or business.

Misconceptions are furthered by the way things are portrayed in the media. "Unprecedented Midwest Flooding" blared one headline. "Flood of 2008 to be worse than Flood of '93" announced another. Which flood was actually worse? It depends. In some places the water was much higher in 2008; others such as the St. Louis metro area on the Mississippi River fared much better than 15 years ago, and overall the Great Flood of '93 was larger in scope than the 2008 flood. Locations such as Iowa City got hit hard both times.

Also, individual major weather events can occur very irregularly. For example, the area around Stuart and Port St. Lucie, Florida, had gone a long time since getting hit by the core of a strong hurricane making landfall from the Atlantic Ocean, yet within three weeks in 2004 the center of two such hurricanes (Frances and Jeanne) came in at nearly the exact same spot.

Then there's the length of those sorts of time periods (100 years, 500 years) vs. the length of the historical record for which good information is available. To confidently assess how frequently on average a very rare event occurs you'd need thousands of years of accurate data, which in this case doesn't exist. Absent that long period of record, values can be extrapolated from recurrence intervals of less-rare events, but that's a dicey proposition.

The amount by which the previous record crest of 20' in 1851 (and tied in 1929) was smashed in 2008 in Cedar Rapids would give the impression that 31+ feet must have an average recurrence interval of at least 150 years and probably much more. But we don't know when the last time that level was reached, nor do we know when it'll be reached again.

In Iowa City, given that the water level during the flood of 1993 substantially exceeded that of 1851, could a valid conclusion be drawn that it'd be at least 142 years before another flood of that magnitude? Look at the height of the crest on June 15, 2008 for the answer. But again, we don't know when that'll be equaled or topped! Will it be in 500 years or 100 years or 10 years or 1 year? (Let's hope not again in 2008!)

Add on top of all that: changes in climate, by whatever cause(s), can in turn change the frequency of weather extremes. (Maybe one reason why the extrapolations don't seem to be working very well lately?)

Plenty of material providing information about 100-year etc. floods has been readily available on the web, such as this and this from USGS, this from FEMA, and even this Wikipedia entry.

The upshot: a "100-year" flood means that based on available data (which might flawed), there's a 1-in-100 (1%) chance of a given location/elevation in a particular watershed being flooded in any given year -- not that a flood will necessarily occur exactly once every 100 years or on any other regular timetable.

July - Peak Month for Thunderstorm Winds

July is the peak month for numbers of damaging wind reports from thunderstorms, averaging about 90 reports per day in the United States. By contrast, May is the peak month for tornadoes and large hail. July ranks fourth in tornadoes and large hail (also trailing June and April). July has averaged 105 tornadoes per month over the past 10 years, and an average July day has about 51 reports of large hail (0.75 inch diameter or larger) in the United States.

Many of the July damaging winds reports come in big clusters, in windstorms called "derechoes." Derecho is a Spanish word for "straight", and these windstorms leave wide, long swaths of "straight-line" wind damage, from severe winds all in nearly the same direction. This can be seen in swaths of downed trees in a forest, for example. Derechoes are widespread damaging windstorms caused by one or more curved lines of thunderstorms, usually bow echoes. As in the first figure below, a bow echo is shaped like the kind of bow used to shoot arrows or like a backwards letter C. An ordinary thunderstorm produces a swath of damaging winds usually only a mile or two wide and a few miles long, but derechoes can produce damage swaths tens of miles wide and several hundred miles long.

One of those derechoes charged from near Milwaukee, Wisconsin across southern Michigan to near Toledo, Ohio on Wednesday, July 2nd. Wind gusts of 60 mph or higher were measured in several locations in the swath of winds across Michigan near or across Muskegon, Grand Rapids, Lansing, Ann Arbor, and Detroit. The radar image below shows the bow echo associated with this derecho at 3:51 PM, north of Lansing. The strongest winds are usually near the leading edge of the precipitation, east of my arrowhead. Often the strong winds begin aloft at about 10,000 feet near the tail of my arrow and descend to the ground northeast of the arrowhead. This descending core of fast winds is called a "rear inflow jet."

The fourth of July has had several well-documented derechoes over the years. One in 1977 caused a swath of downed trees up to 17 miles wide and 166 miles long across northern Wisconsin. Its winds were up to 135 mph, and it caused $24 million in damage, 35 injuries, and one death. Another in 1999 blasted from Fargo, North Dakota across northern Minnesota. It caused $85 million in damage in Fargo and $12-18 million in timber damage, including in the Boundary Waters Canoe Area Wilderness, where 20 campers were injured.

The figures below show examples of some notable recent derechoes. The first figure shows the swaths of damaging winds from a pair of derechoes that hit St. Louis, Missouri, two days apart on July 19 and 21, 2006. The first one moved southward, packing wind gusts up to 92 mph. Thirty people were injured at the baseball stadium where the Cardinals were preparing to play the Atlanta Braves. Downed power lines left about 590,000 customers without power.

Service had been restored to about 270,000 of the customers by the time that the second derecho rolled in from the west on July 21. This second derecho sent the number without power back up to 560,000!

The next figure shows the damaging wind swath from a derecho that blasted Memphis, Tennessee on July 22, 2003. It produced the largest blackout in the city's history, leaving 338,000 customers without power, some for up to 15 days. This long-lived derecho reached Atlanta, GA and beyond in a somewhat-weakened intensity.

Another infamous derecho raced at a speed up to 75 mph from northern Michigan across Ontario and into New York and southern New England on July 15, 1995, shown in the figure below. Wind gusts were measured of at least 92 mph. The derecho caused 7 deaths and nearly a half billion dollars of damage.

Because of the widespread nature of the winds in a derecho, the impact is somewhat like that of a landfalling hurricane, and affects a much greater area than most tornadoes. The extensive swath of downed trees and power lines causes a major cleanup and restoration effort that takes days to weeks and often requires relief workers to come in from other states to aid in these efforts.

Latest on Bertha and the Gulf moisture

[Updates follow original entry; latest as of 2:30 am EDT Tuesday July 8]

BERTHA

As illustrated by this satellite image from the NASA Earth Science Office, Bertha has intensified dramatically since yesterday, now officially a high-end Category 1 ...

... but it still remains far from land.

And the only land area in play for a potential direct impact in the *foreseeable* future is Bermuda.

In an interesting coincidence, 1996's Bertha also became a hurricane on July 7!

Recognizing the standard caveats (pre-satellite-era lack of info; modern era NHC subjectivity) ... and if I'm correctly gleaning from the NOAA map below on which I've done my best to precisely place the point where Bertha was designated a hurricane this morning ...

It's unprecedented in the historical record for a tropical cyclone to reach hurricane intensity this far east in the tropical Atlantic this early in the season (or in all of July for that matter).

The map shows all July storms; red track lines indicate hurricane intensity (Cat 1-2).

The only July hurricane farther east was later in the month, and that one was outside the tropics, in fact unusually far north, becoming a hurricane at nearly 40N (Danny in 2003).

[Click image for larger version.]

GULF OF MEXICO

Although there's been another blow-up of convection (rain & thunderstorms) in the western Gulf of Mexico, reminiscent of the one early Saturday, conditions are unfavorable for this system to pull a stunt like Humberto and Lorenzo did last year in the western Gulf and suddenly become a hurricane.

Its main effect is therefore expected to continue to be rainfall, and lots of it. This means additional drought relief for extreme southern Texas. What we don't want is too much to fall too quickly, though, and the NWS has now issued flood advisories for the areas west of Brownsville.

I haven't seen any reports on the wire -- yet -- of serious flooding south of the border, and hopefully that will continue, but with the heaviest rain continuing to fall in Mexico, the threat still exists there, and it will increase if that area of downpours south of Brownsville remains concentrated and persistent.

[Image source: GRLevelX]

UPDATE 4PM EDT MONDAY JULY 7

This season's first classic MODIS satellite image of the eye and inner core of a hurricane is in, and it's nice to be able to marvel at the sight without any land areas being imminently threatened. There's nothing particularly unique about the features in this image, but these high-resolution images are always spectacular to look at!

(Yellow lines indicate latitude and longitude; this is a crop of the full image, which can be seen by clicking here -- for maximum effect, don't resize image to fit screen.)

The National Hurricane Center will almost certainly bump up the official intensity on their next advisory.

[Image source: Naval Research Laboratory]

For those of you who have posted comments about your concern in regard to the Caribbean, Bertha is not headed in that direction. The only land area currently in the potential path during the next five days is Bermuda, but it's too early to know exactly how much impact will occur there.

UPDATE 5PM EDT MONDAY

NHC has upped the official intensity to a low-end Category 3, which makes Bertha the first major (Cat 3+) hurricane of the season.

UPDATE 2:30 AM EDT TUESDAY

Bertha is still a healthy major hurricane, but that ironically is good news. As I noted in a comment in response to readers' questions, by becoming a stronger and deeper circulation, it has felt the influence of a mid and upper level trough and has been tugged a bit farther north, rather than being steered by the low-level flow as is typical of weaker, shallower circulations, in this case more westerly.

This in turn has decreased the probability of it having a significant direct impact upon land. At the risk of jinxing it, the chance of a U.S. landfall appears to now be virtually nil.

In addition, the odds have increased for the core of the hurricane to miss Bermuda to the east. It's too early to be sure of that, and folks living in or traveling to Bermuda still need to monitor the latest forecast; that's the latest trend, though.

With that Gulf system, here are the latest rainfall totals north of the border, with yet another batch of heavy rain at this hour south of the border.

[Click on rainfall map for larger version.]

Bye bye Bertha?

[update follows original entry]

Well, almost, but not quite yet. Bertha has been resilient to hostile atmospheric forces in its environment (dry air and "shear"). After looking sick yesterday, the hurricane has become better organized again last night and this (Wednesday) morning.

[Source: Naval Research Laboratory; I've circled Bermuda]

And although its core may ultimately not hit any land areas, the steering currents are going to get more nebulous with time, which means there's uncertainty in the details of the outcome. Note the key word: details. In the big picture there's a high confidence of what's going to happen.

The hurricane is not a direct threat to North America (and although there were was some sensationalistic stuff out there on the web, that was a long shot at best.). Indirectly, it'll generate waves which will head toward the East Coast.

Eventually, Bertha is expected to head out to sea. Sometimes when tropical cyclones meander out in the Atlantic, the meteorological players can evolve in such a way as to, lo and behold, suddenly cause them to make a beeline toward North America. Jeanne's track in 2004 was a classic example of that.

[Source: National Hurricane Center; click on image for larger version]

However, rather than a ridge of high pressure building to the north and northwest of Bertha like was the case with Jeanne, a trough of low pressure will develop in the western North Atlantic this weekend and early next week, which will prevent any additional westward movement.

Before that happens and Bertha goes completely bye-bye, though, it could move painfully slowly for awhile, and exactly where it is at the time and how much it expands in size will determine the effects in Bermuda, and whether the islands just receive waves and perhaps some outer fringes of wind/rain, or more substantial and prolonged wind/rain. It's gonna take a number of days for this to play out, but right now the former is more likely than the latter.

UPDATE 4PM EDT WEDNESDAY JULY 9

Although somebody posted a comment suggesting that maybe Arctic ice cooled the water and killed Bertha, actually water temperatures in most of the North Atlantic are running above average, and the hurricane weakened yesterday while moving over increasingly warm water. And now, rather than being killed, it's making a big comeback, increasing again in both intensity and size.

It's not moving any farther west than expected, though, so the scenario for Bermuda remains unchanged.

How long will Bertha last?

[Sunday July 13 update follows original entry]

Bertha slowing down to a painfully slow crawl as steering currents became weak and nebulous was not unexpected; it was just a question of exactly where, and it's happened a couple hundred miles southeast of Bermuda.

Although bigger in size than it once was, Bertha is a shadow of its former self intensity-wise. The aircraft reconnaisance that just arrived reported a central pressure 984 millibars, or 29.06", in the middle of the large 57-mile diameter eye, up from what it was yesterday and undoubtedly much higher than at Bertha's peak (when there were only satellite estimates). In general, the lower the pressure in the middle of a hurricane, the tighter the pressure "gradient" and the stronger the winds.

Also, the convection (deep thunderstorm and rain clouds) is less robust and more disorganized than earlier in Bertha's life. So while Bermuda will at least be brushed by Bertha, its intensity and track will mitigate the effect there unless the hurricane were to suddenly reintensify a lot and make a beeline northwest, which is not likely.

Bertha is now one of the longest-lived tropical storms and hurricanes on record in July, and its longevity has already exceeded that of any storm in the 2007 season!

The question has been whether the weather system which brought severe weather to Minnesota and thereabouts on Friday would fling Bertha away once and for all. It'll probably give Bertha a shove, but downstream over the North Atlantic between Bermuda and Europe, the steering pattern is about to get rather blocked up.

While Bertha may subside below hurricane intensity, and the precise answer to the question in the title of this entry is unknown, it's going to continue to hang around as a tropical cyclone for quite awhile.

SATURDAY EVENING ADDENDUM

This is the peak of the beachgoing season in the Mid-Atlantic and Northeast, and please be careful in the water. There were many rescues today and the rip current risk will be quite elevated again tomorrow as a result of swells from Hurricane Bertha.

UPDATE NOON SUNDAY EDT

Bertha is still not moving much, although it may have begun a slow NNW drift. There's a well-defined swirl on visible satellite imagery (top), but the infrared image (bottom) shows that the convection (deeper clouds) is weak and disorganized, and NHC has finally lowered the official intensity to tropical storm status.

Meanwhile, the next system to monitor ("invest 94L") in the tropical Atlantic is east of the Lesser Antilles.

There's also a large low-cloud swirl centered east of Virginia Beach, a small spin evident on satellite loops just southeast of Myrtle Beach, and a zone of showers and thunderstorms from the eastern Gulf to the Bahamas. No tropical cyclone development is imminent, but all of this, in combination with Bertha and 94L, seems to be a sign that the atmosphere is primed as we head toward the peak of the season ...