For a birds-eye perspective on what swells can do to an ocean-going vessel, sit down, put all food out of arms reach, don't eat while watching this, and click on this clip I found from Youtube. Although this is a ferry, you can just imagine what the passengers are going through.
If you are unable to view the video, just this one picture says it all about what happens when YOUR DREAM VACATION cruise you've saved up all year for encounters swells. So if you have reservations to cruise this weekend in the Western Atlantic, please don't let me scare you off..just know it might be a bit rough and BRING THE DRAMAMINE! Note: This picture is not photo-shopped.. it is the Voyager in swells of the Mediterranean.
MONDAY 7-7 AM UPDATE: Sorry, I just couldn't resist that one, (Bears Watching) for it's been 3 years since this particular headline was last used. As you probably already know, Bertha is the first hurricane of the 2008 Atlantic Tropical Cyclone season. What you may not know is exactly 12 years ago to the day...July 7, 1996, we also had a Hurricane Bertha in the Atlantic. Another interesting twist is that this storm has given a restaurant in Fell's Point Baltimore a unique if temporary notoriety. As reported by the Sun newspaper, Bertha's is offering discount hurricane drinks, the portion size of which may increase as the storm strengthens. Those who frequent Fell's Point know it is the place to eat Mussels, and now perhaps a new tradition will be born in Charm City... thanks to the tropics.
You'll notice a sharp decrease in the distance Bertha is projected to travel from Friday to Saturday. Influence from the subtropical (Bermuda High) is likely to play a major role in where the hurricane ends up making her final run, as well as interaction with a frontal boundary moving east from the Great Lakes in the middle and latter part of this week. I am beginning to woder if the weekend track of this storm will resemble that of Hurricane Jeanne in 2004, which meandered off the Florida coast for nearly a week before making landfall. I'm sure our instructor, Lou McNally of the Weather and Climate Class will be continuing to make this a teachable moment for my colleagues and I. As we get to apply new forecasting skills from class, I'll be updating further on what I think are Bertha's plans for the weekend.
SAT 7-5 AM UPDATE: The Tropical Atlantic is starting to produce noticeable activity, view the latest infrared satellite loop. As of 11AM Thursday morning, the robust tropical wave off the West African coast was upgraded to Tropical Storm Bertha, and may approach hurricane strength late in the weekend.
SYNOPSIS: Bertha is the first named tropical storm known to have developed this far East in the Atlantic. At present, upper level air flow patterns indicate that a landfall on the U.S. mainland cannot be ruled out. In the southeast Caribbean, a weak area of low pressure had been producing scattered showers and thunderstorms, but remains disorganized. However, activity continues to flare up west of the estimated center as the overall system drifts west-northwestward. A broad area of showers and thunderstorms is also present near the coastal Texas/Mexico border and will be monitored this weekend.
FIRST, THE CAPE VERDE SYSTEM: View this enhanced infrared loop. Ironically the last notable tropical cyclone to form in this region at this time of the year was...Bertha, in July 1996. With a classic summertime Bermuda High ridge forecast to start building next week, one might initially think the storm could travel under the ridge and in the general direction of the Caribbean. When considering the air flow at upper levels, a different trend is revealed, and you would see why some computer models are indicating recurvature east of Bermuda. A brief explanation for this is provided in the "upper level analysis" section. Below is the current NHC projected path from 5PM 7-4, and preceding it is the 11AM Advisory.
Notice the westward shift in the cone of uncertainty from one map to the next.
UPPER LEVEL ANALYSIS: This next map is among the many new features I've been learning about in my Weather Forecasting and Climate Change class here at the picturesque College of the Atlantic. As I experiment with a new feature or skill from the class, it will be added here for use during this year's hurricane season. The newest (to me) resource is the 500 mb 24-hour forecast for the Central and North Atlantic issued by the Ocean Prediction Center. The inference I am making from this map is that once Bertha nears the Low and High progged at the 500 mb (~18,000 foot) level, the air movement between these two centers will create convergent flow south to the south side, with air diverging on the north side. This will act to pull the system toward the vacuum created by this flow, and begin curving the storm northwest and eventually northward into the central Atlantic. The NHC refers to this as a weakness in the subtropical ridge. This is an example of the importance of knowing movement of air masses and pressure differences at upper levels, which ultimately dictate what is observed on the surface for us ground observers.
BACKGROUND: A tropical wave developing off the West African coast is referred to as a "Cape Verde" system due to the promixity of an island cluster of the same name. Were this occuring between mid August and late September, we would have great cause for concern. This early in July, waves way out there usually don't become the Katrinas, Ivans, Floyds or Glorias and come terrorizing the Gulf or East Coast. Each tropical season, one hundred or more disturbances drfit off the African coast and cross the Atlantic. In July 2005, two of these systems reorganized once near the Caribbean and developed into named storms. Dennis made landfall as a Category 3 Major Hurricane on the Florida panhandle July 10 of that year. Just eight days later, Emily has already crossed the same southern Caribbean waters, and struck the Yucatan on July 18 as a Category 4. Emily also had a second landfall south of Brownsville in Northeast Mexico as a Category 3. I realized in reviewing the archives on both storms...back on July 6, 2005 the Atlantic basin had nearly an identical setup: A tropical wave just off the African coast (which would become major Hurricane Emily), AND a small feature in the southern Caribbean which became Dennis.
While this system has decated, compare the earlier projected path to the NHC official tracks for Hurricane Dennis in July 2005, as recorded in this link to the archives for that period.