Saturday, July 5, 2008

DOUBLE TROUBLE AHEAD:
1. CAPE VERDE TROPICAL STORM...RECURVING?
2. INSTABILITY IN THE WESTERN GULF

Atlantic Basin 7-4

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.

Bertha 3

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.

Bertha 2

Notice the westward shift in the cone of uncertainty from one map to the next.

NHC Bertha 2

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.

Atlantic 500MB 7-3-08

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.

SECOND: THE SOUTHERN CARIBBEAN SYSTEM. View the latest satellite loop. While the system is being sheared by upper level winds, it is also about to enter surface waters nearly 2 deg F above normal, and low level steering currents favor a west-northwest path for the next day or so. Despite the shearing, thunderstorms continue to flare up west of the center. Closer examination of the environment ahead of this wave is warranted over the weekend. Any system named in that region of the Atlantic Basin this time of year will be a cause for concern among emergency management officials, cruise operators and the especially oil market. In fact, I suspect that many astute futures traders are watching this area closely For an even more serendipituous perspective on the economics of hurricanes, consider investing in the Hurricane Futures Market, as first reported by MSNBC in 2005. As Dave Barry would say, "I am not making this up."

Invest 93L Satellite 7-2

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.

Invest 93L Preliminary Model Tracks

Under the training from our Weather and Climate Instructor, I've gained a new appreciation for the importance of applying real time interpretation skills to existing atmospheric data. I've spent the learning from Dr. Lou McNally, who with 30 years service across in both the private and public forecasting industry, is a super-rich source of knowledge and we are very fortunate to have him take time out of his crushing schedule to shepherd us through the nuances of weather analysis. Thanks Lou, for making this a highly informative, useful and thought-provoking class thus far! For me it is uniquely fun and beneficial, as I have been implementing the skills learned in class almost immediately, and hopefully those of you following this site will see the payoff in a better understanding of what drives the weather.


PREVIOUS UPDATE- WED 7/2 4:30 PM. From beautiful Bar Harbor in Downeast Maine, I wish you all a safe and weather-friendly Fourth of July Weekend. I shall have the day off from my Weather Forecasting and Climate Change course here at College of the Atlantic. If our class forecast for the weekend holds true, then I plan to revisit Acadia National Park via the island bus service and take my rented mountain bike with me. During lunch each day, I take a short bike into the wonderfully quaint town that is Bar Harbor (yes I will post pictures soon). On Tuesday 7/1 my classmates and I journeyed atop Cadillac Mountain for incredible views of the Maine coastline as well as cloud and front analysis. At 1,530 feet, this mountain is the highest point directly on the Atlantic coast north of Brazil, and it is quite a sight to look out into the ocean from it's summit. Thank you to the well-wishes of those whom have made Bar Harbor among their vacation spots, and I can now see why you think so fondly of this place. As I pedal through the rustic and unique downtown, I think fondly of all you as well and wish you along with my family could be here to enjoy the sights, fresh Atlantic air, and great people that comprise the wonderful region known as "Downeast Maine."

6 comments:

NeedaSnowday said...

GREETINGS MR. FOOT!

What a treat to get some updates from you... hope you are enjoying your time up North!... thanks for keeping us updated on the summer happenings... having a family cottage located on Hoopers Island -I am always attentive the the possiblities of hurricanes... Isabel got us good!!

Mr. Foot said...

Thanks NASD.. it is indeed a wonderful time here in Downeast Maine. I'm about to head out for biking and kayaking with some colleagues. Wanted to mention that I did not do a full update this AM, as looking over upper air charts more for the Atlantic. At some point very soon, I imagine Emergency Mgmt is going to start inquiring on the one question...
"Is this going to hit us?"

Those discussions may have already started. And the plot thickens.

More later today after the 5PM NHC update.

Mr. B said...

Mr. Foot,

How are you? I am in NC. Just as boring as as home wea\ther wise. No storms for weeks.

Mr. Foot said...

mr. b.. what part of NC? If you're near the coast, you can't say it's boring... go rent a bike, sail a boat, swim, catch rays, build a sandcastle. I could come down and demonstrate some of these things when I'm done in Maine.

Another fun activity would be to go have the locals tell you hurricane stories! Fran, Ophelia, Floyd, Bertha, Isabel to name a few.

Enjoy your time off now, I think t'will be a busy 'cane season, followed by a busy winter.

Mr. B said...

I am in Burgaw, nc about 30 from Wilmington. I go to the beach on Mondays. Topsail beach. It's freak'n nasty humid here today. Sunny and 88 already. Dewpoint like 1000. lol. I hope we actually get so weather action this tropical and winter seasons. I will returning to PA on the 19th anf then going to cedar point and Johnstown, pa till the 28th.

Julee said...

Uh-oh Mr. Foot ... that Tropical Atlantic is a MESS! The Gulf isn't looking so good either. I think you'll be VERY busy in a few days.

Your pix are beautiful. You should make a calender for your girls! Glorious place for you to spend some summer days.

Thank you so much for sharing your working vacation with us. Kennebunk is as far into Maine as I have been, and I immediately fell in love with that coastline -- flora, fauna and vista!

As always, looking forward to your wintery forecast.