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Two Signs Of Life In The Atlantic Hurricane Season As Labor Day Approaches

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A few weeks ago virtually every seasonal hurricane forecaster adjusted its projections downward for the Atlantic hurricane season. The primary reasons cited were that Atlantic waters were relatively cool and an El Nino was expected to develop. I wrote a Forbes piece discussing the new projections and why forecasters were making the adjustments. There were two things that I mentioned in that article worth repeating. First, the statistical peak of the Atlantic hurricane season is in September. Second, I cautioned "even with all of the talk about 'below normal' please stay diligent in coastal communities because it only takes one storm." As I take off my Forbes contributor hat and place on my meteorologist cap, I see two signs of life that suggest the Atlantic Hurricane Season is awakening from its slumber, and one of them could impact the U.S.

NOAA and tropicaltidbits.com

Meteorologist and FEMA strategic planner Michael Lowry summed it up best with this tweet,

Only two years in the modern record - 1968 and 1994 - haven't recorded a #September #hurricane. @NWSNHC forecasting #PTC6 to be a hurricane by Sunday (Sep 2nd). Average number of Atlantic hurricanes in September is three.

Lowry, a former hurricane expert at The Weather Channel, is making the point that it is pretty uncommon to not have some tropical activity during the month of September. The graphic below illustrates where storms typically form in September, and we are seeing activity in those locations. At the time of writing, the National Hurricane Center is tracking two systems and possibly more in the weeks ahead. An advisory on Potential Tropical Cyclone Six, issued at 8:00 AST Friday, provides the latest information:

At 800 AM AST (1200 UTC), the disturbance was centered near latitude
13.7 North, longitude 21.8 West. The system is moving toward the
west-northwest near 12 mph (19 km/h), and this motion at a slightly
faster forward speed is expected to continue for the next three to
four days. On the forecast track, disturbance is expected to move
near or over the southern Cabo Verde Islands as a tropical storm

later today and tonight. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast during the next several days, and the disturbance is expected to become a tropical storm later today or Saturday.

NOAA

Cape Verde-type hurricanes form within 600 miles of the Cape Verde Islands primarily in August or September. At this time of year, there is typically ample tropical wave activity, deep warm waters, and weaker wind shear. However, water temperatures in that region have been anomalously cool much of the summer. The sea surface temperatures (below) west of the Cape Verde Islands are finally starting to creep up to the 28 to 30 degrees C range needed for optimal tropical cyclone development. The National Hurricane Center gives this "typical" Cape Verde system a 90% chance of further development to "Florence" in the next 2 to 5 days. Our best models do not have the storm approaching the U.S. mainland or the Caribbean Islands.

NOAA

However, the National Hurricane Center is watching a system a bit closer to the U.S. that could put a damper on some Labor cruise or vacation plans in the Caribbean Islands. It is a system that people along the Gulf Coast states will need to watch next week also. The latest thinking from the forecasters at the National Hurricane Center on this is:

Disorganized cloudiness and showers from Hispaniola eastward to
the Leeward Islands and the adjacent waters are associated with a
tropical wave interacting with an upper-level trough. This activity
is forecast to spread westward to west-northwestward enhancing the
rainfall across portions of Hispaniola, the Bahamas, the Turks and
Caicos Islands, and Florida into early next week. Strong upper-level winds will prevent any development of this system during the next 2 to 3 days, but environmental conditions could become less hostile when the system reaches the eastern Gulf of Mexico during the early to middle part of next week.

Though only part of the story, the sea surface temperatures in the Gulf of Mexico are favorable for storm development, but other meteorological factors will need to be considered in the coming days.

Going forward, some tropical experts have pointed out the possibility of more tropical activity in the next 1 to 2 weeks based on model projections. However, the National Hurricane Center tweeted this wise cautionary note:

NHC's Tropical Weather Outlook provides 48-hr and 5-day chances of tropical cyclone formation. Long-range model forecasts of tropical cyclone formation beyond 5 days are often unreliable and can show large variability between models and from one model cycle to the next.

Climatologically, the 6th named storm in the Atlantic comes around September 8th. I am writing this on August 31st. If the aforementioned Cape Verde system gets a name, it will be the 6th storm of the season (Florence). The lesson is that even though a "below-normal" season has been projected, we are actually ahead of climatological average right now.

NOAA

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