Sunday, August 30, 2009

WE'VE ENTERED THE ZONE

SYNOPSIS
The Atlantic basin is entering the historical annual peak of tropical cyclone activity, represented by the two week period on either side of September 10.
Relatively few hurricanes in 2009 may have permitted areas of the western Atlantic and Gulf of Mexico to experience warmer-than-normal sea surface temperatures.
El Nino is present in the equatorial Pacific and expected for duration of the 2009-10 Northern Hemisphere winter.
These and other indicators may signal a snowier winter for the Eastern United States, concurrent with the possibility of an earlier than usual start to the winter storm season.

10:00 AM Sunday, 8-30-09 The Atlantic Basin is nearing the climatological "high water mark" of tropical cyclone activity, historically peaking on September 10. The next two or three weeks may turn out to be the most active period of the entire season. However, a strengthening El Nino signal in the equatorial Pacific may continue influencing westerly shear enough that any developing systems spend more time looking like a threat than turning into one. On the cautionary side, sea surface temperatures (SST) in the Gulf of Mexico are at or above the seasonal peak, with large areas 86 F or greater. All of us coastal-types are not only entering the school zone, but also the hurricane primetime zone. With the 4-year anniversary of Katrina a painful reminder, anything tracking across the Altantic for the next 2-3 weeks bears close monitoring.


For snow-starved powderhounds, the current SST trend is a strong indicator of what dreams may come this winter. I closely monitor Global SST anomalies in the fall as a key signal of what winter may bring. A prime example of this hypothesis is the winter of 2002-03. Hurricane Isabel was the only notable system to significantly affect the East Coast, during a weakening El Nino with Pacific temperature anomalies averaging 1.0 C. Moderate shear influenced by those Pacific anomalies finally relaxed in mid September 2003, permitting Isabel to make her unstoppable westerly beeline for the East Coast. This year, El Nino is stronger, with "sea surface temperatures across the equatorial Pacific .5 to 1.5 C above average," per the Climate Prediction Center's weekly report. The CPC goes on to say, "Current observations and dynamical model forecasts indicate El NiƱo is expected to strengthen and last through Northern Hemisphere winter 2009-10. For snow-starved Mid-Atlantic powderhounds, this could be a very good sign, and a source of my hypothesis.


This hypothesis is centered on two seemingly unrelated events: (1) A strengthening El Nino increases potential for disruptive westerly wind shear in the Altantic basin; and (2) Wind shear that reduces or deflects the impact of tropical cyclones near the coast permits SST's to reach warmer-than-normal levels in certain areas. Undeniable evidence is plain to see in the current Caribbean SST anomaly map as of 8/27/09, as denoted by the "blue swath" indicating the path Hurricane Bill followed in mid-August.


What's the connection to a snowier winter? Just keep reading, we're almost there. But compare the Atlantic SST data to the Gulf of Mexico on that map. Notice that large areas of the Gulf are at or near 86 F (30 C). Whatever energy not removed from the water by tropical activity during summer may persist into winter. That energy can be tapped by developing winter storms crossing the southeast in the much the same manner of the President's Day Storm in February 2003. Although 60 or more days remain for the tropics to "stir things up," with some water temperatures already well-above normal, it will take several strong systems to put a dent in those levels. There are several more factors that must take their place in the "Circle of Life" as it pertains to a snowier signal for this winter, among them trends in the North Atlantic Oscillation, Northern Hemispheric snow cover, Arctic sea ice, and most importantly tracking the snowline descent from Canada each fall. The National Ice Center has links to useful daily imagery.

The long and short of it is this: I hypothesize a high probability winter 2009-10 in the Mid-Atlantic produces at least the climatological "normal" amount of snow (for example, a 30-year average of 19.2 inches at BWI). If the trends continue, perhaps we will see a whole lot more. The real answer that administrators and district-level employees seek is simply: "That's nice for the teachers, but will it be ENOUGH to close schools AND offices? ;-)

Wednesday, August 26, 2009

ANOTHER WAVY WEEKEND

8:00 am Friday, 8-28-09. Just when you thought it was safe to go back in the water, the Coastal Mid-Atlantic and Northeast for the second time in a 10-day period will face effects from a tropical cyclone. The primary impacts will be another frustrating weekend for beach-goers, boaters and lifeguards alike as Danny's passage will produce high surf conditions and dangerous rip currents. Luckily for coastal residents, this will not resemble the period of late August to early September in 1999, when Hurricane Floyd delivered 12 or more inches of rain on areas still saturated by Hurricane Dennis the week before. Residents of North Carolina can never forget the horrific aftermath of Floyd, with catastrophic flooding that destroyed millions of cattle and ruined thousands of square miles of agricultural land. While Danny is not likely to patch that kind of punch, it is worth noting from a climatological perspective two back-to-back tropical systems taking a similar path along the East Coast. With yet another area of disturbed weather in that critical "Cape Verde" region of coastal Africa, is Mother Nature hinting that Danny and Bill were sent just to lay the red carpet for... Erika?

WHAT WILL DANNY DO? By examining the historical tracking map (paths of previous August tropical storms), and compare that to the current computer model projected paths for Danny as of 7:00 AM Wed, there is comfort in the trends. Both historical data and model output suggest Danny DOES NOT make landfall along the Mid-Atlantic or Northeast unlike Floyd or Isabel (as shown by the StormPulse site). However, it goes without saying that lifeguards, boaters and beach-goers alike face . NOAA reconnaissance aircraft will continue to investigate the storm several times a day, and if the storm reaches Hurricane strength, you'll be among the first to know by monitoring the "Vortex Data Message" on the NHC site.

ON POST FREQUENCY For my colleagues in education, it comes as no surprise that with our return to school in advance of the students, the frequency of posts will be diminished for a time. To bridge the gap and maintain meaningful content, I have a report in development that discusses quantitative data of trends heading into the winter pattern. This post will likely have to wait until Danny has moved on, but in the draft version right now are four key climate indicators which will form the basis of my prediction for the winter storm season.

The four indicators:
(1) Impact of the Solar Minimum on atmospheric temperatures;
(2) Current state of El Nino and effect on North America this winter;
(3) Sea surface temperature anomalies in Gulf of Mexico, western Atlantic and central Pacific;
(4) Evidence of a "negative trend' for the North Atlantic Oscillation (NAO) for fall and early winter.

A majority of this report is written, and it will be presented as soon as time and school preparations permit, but not before the weekend. Until then, we have something new to talk about, so onward with the discussion topics, such as "What will Danny do?" or "Do you remember Floyd?" or "Will this affect the start of school?"

Saturday, August 22, 2009

Wednesday, August 19, 2009

In motion on the ocean...

Bill's current wave heights 8-19-09

9:00 am WEDNESDAY 8-19-09 Today's headline is straight from Enya's "Anywhere Is" in the 1995 album Memory of Trees and fits perfectly within several venues:

1. If your cruise ship is sailing East Coast waters this weekend, ocean motion may cause a few problems while completing the 1-2 "fun days at sea" en route to or from the Carribbean. Look carefully at the Ocean Prediction Center's map above, you'll notice the wave heights in and around Bill presently. See that number in the right corner? That's not a typo.

2. Coastals* may be in motion heading to the ocean, but by Saturday the best-laid plans could screech to a halt once reaching the beach. Dr. Steve Lyons of the Weather Channel suggested last night that wave heights of along the Carolina coast and near mouth of the Chesapeake Bay will build to the 6-9 foot range on Saturday. According to NOAA's WaveWatch, by Sunday morning, waves along the Maryland, Delaware and Jersey coasts could exceed 12 feet. Maybe boardwalk restaurants should offer special menu pricing and front row seating for weekend wave watching.

In using NOAA WaveWatch, to see projection, click the pull-down menu at "info page" and select "North Atlantic hurricane (reg.)" and click "go." Then you can scroll forward in time using the right arrows.

From the Wakefield, VA National Weather Service's 4:25 AM 8-19-09 Discussion for MD/VA Coastal areas:
REGARDING RIP CURRENT DANGER...WL CONTINUE WITH LOW RISK TODAY. HOWEVER...INCREASED RISK LIKELY FOR (AT LEAST) FRIDAY THROUGH THE WEEKEND AS SEAS CONTINUE TO BUILD. LONG PERIOD SWELL IN ASSOCIATION WITH HURRICANE BILL WL CONTINUE TO PROPAGATE/ARRIVE ALONG THE EASTERN SEABOARD THU/FRI...AND A HIGH RISK OF RIP CURRENTS LOOKS TO BE LIKELY THROUGH THE WEEKEND. TO MAKE MATTERS WORSE...A NEW MOON OCCURS ON THURSDAY...WHICH WILL ALSO CONTRIBUTE TO THE ELEVATED RIP CURRENT THREAT. IF YOU ARE PLANNING ON TRAVELING TO THE BEACHES LATEIN THE WEEK/THIS WEEKEND...REMEMBER TO ALWAYS HEED THE ADVICE OF THE LOCAL BEACH PATROL/LIFEGUARDS AND CHECK PRODUCT WBCSRFAKQ FOR THE LATEST THREAT AND SURF ZONE DETAILS.
* Today marks the introduction of this new Foot's Forecast term denoting those readers who count spending time at the beach of equal or greater importance as witnessing a heavy snowfall. Now all you powderhounds finally have an appropriate off-season identity. This is designed to provide you cover during those uncomfortable dinner-party moments in the summer when the topic of snow comes up, and while sweating on the portico sipping a mint julip, you fruitlessly explained to friends why just love heavy snow and cold weather. Example conversation:

Conditions: 94 F, humidity 86%, wind: calm. Location: Ocean city, MD beach at 120th street.

Friend: "It's been such a strange summer, I wonder if this means we'll have the same kind of bizarre weather this winter. I've heard there are some really strange people on the internet that, like, follow this stuff 24-7."

You: (using your stained right sleeve to wipe away forehead sweat) "Well, I don't know anyone like that, but for me personally, I enjoy super hot weather, as long as I'm at the beach when it happens. But I also really look forward to those long cold stretches in the dead middle of winter-- you know when the ground is all covered in a pristine blanket of crystal white snow -- and (excitedly) and the sun has just come up, casting this beautiful bright fan of light across the landscape. So I call myself a "coastal" because I love hot weather at the beach, and cold, snowy weather at home caused by big coastal storms. Makes sense, right?

Friend: (period of silent perplexed look) "Uh huh. (Gets up) So anyone need another drink?" (Leans down to you and says) "As for you..no more of that 'Ocean motion potion' bucko."

Monday, August 17, 2009

HE'S GOT THE LOOK

Hurricane Bill 5:00 PM EDT 8-17-09

6:00 pm MONDAY, 8-17-09 This headline is a slight take-off of the 1988 pop hit "She's Got The Look" by the artist/group Roxette, but I think we can all agree Bill is starting to get "the look" himself. Recent NOAA satellite scans this afternoon suggest the hurricane is starting an eye-wall replacement cycle (ERC) which is usually followed by rapid intensification. Category 3 status seems very likely in 24 hours or less. All those with weekend plans for the coasts of the Carolinas, DelMarVa or New Jersey may be faced with a lot of unexpected beach closures. Yes, I know some of you made a deposit on that beachfront rental back last October. But Mother Nature is probably going to beat the Route 50 Bay bridge traffic Friday afternoon, and be waiting for you just across the dunes with a little surprise in big red letters: BEACH CLOSED.

AND SO IT BEGINS...

7:00 am MONDAY, 8-17-09 With a rush of headlines and three storms forming in two days, it's apparent the Atlantic basin has awoken from a long summer slumber. The real questions for tropical watchers are simple:


1. Does Hurricane Bill pose a threat to the East Coast?
Early indications of the projected path suggest that Bermuda may feel more direct effects from this storm, whereas the US East Coast could experience several days of dangerous rip currents.


This week, two upper level features will be of primary influence to Bill's track: The 500 millibar Atlantic Ridge as shown on this forecast map from the Ocean Prediction Center (OPC), and an upper level trough sliding across the central US. While the hurricane travels around the southern pheriphery of the Atlantic ridge, it will enter a confluence zone created by the clockwise flow around that ridge, and the counter-clockwise southerly flow generated by the trough. The combined effect of these two features is likely to veer Bill from the current westerly track to more northwest as shown in the NHC graphic, and eventually north-northwest by the weekend. This expected turn is also reflected in the tropical cyclone early-track guidance provided by Colorado State University and depicted on the interactive site StormPulse.com. Based on this analysis, some media forecasters suggest that Bermuda is more likely to experience effects of this storm.


References:
Kimberlain (2009): Hurricane Bill Discussion 8 from National Hurricance Center's 500 AM EDT 8-17-2009 update. Retrieved August 17, 2009 from http://www.nhc.noaa.gov


By Friday, rip currents and swells will increase along the southeast coast, and by Saturday affect the entire Eastern seaboard from Florida to Maine. This will pose a significant hazard to swimmers, beachgoers and lifeguards. You can monitor the progress of swell heights with the OPC's Wind/Wave Analysis. Hopefully local and national media will convey the shoreline's hidden dangers enhanced by a passing hurricane. Of particular concern will be ocean-going cruises departing from or returning to East coast ports. If you are among those hopeful travelers, be prepared for changes in the itinerary, or at least be cautious in how much you consume at the dining hall! (I assume you understand the connection.)


2. Do these storms signal the start of an active period heading into September and the all-important Labor Day Weekend? As you can plainly see from the StormPulse visible satellite image below, a series of tropical waves is in the queue ready to keep forecasters busy for at least the next 2 weeks.

African Waves 8-17-09


Answers to those in addition to your questions will be posted in the next day or two.