By Crown Weather
Summary: I am expecting that the 2018 Atlantic Hurricane Season will be about average in terms of activity. One reason for this is due to the fact that we are slowly transitioning from La Nina conditions into either neutral ENSO conditions or a weak El Niño during this summer into this autumn.
It needs to be pointed out that the forecast for the 2018 Atlantic Hurricane season is a difficult one due to the fact that it is uncertain whether we will see El Nino conditions form or whether we will see a repeat of last year where we had a failed El Nino and instead we transitioned back into La Nina conditions. If the forecasts for El Nino are incorrect and we end up with another La Nina, then we could see a much more active hurricane season than what we are forecasting right now. On the other hand, should a full fledged El Nino develop during the summer, then we could see a very inactive hurricane season with numbers that are much lower than what we are forecasting right now.
In addition, I am expecting the formation of at least one tropical storm in the western Atlantic during either May or early June. In addition, I also think that we could start out “quick” with tropical storm/hurricane formation from May to August, but then slow down in activity during September with the hurricane season potentially ending early in October as El Nino strengthens and attempts to make the Atlantic increasingly more unfavorable for development.
The Numbers: 14 Named Storms, 7 of those storms becoming Hurricanes and 3 of those hurricanes becoming Major Hurricanes (Category 3 or higher on the Saffir-Simpson scale).
Accumulated Cyclone Energy (ACE) Index Forecast: I am forecasting an ACE index this year of 100. This number basically says that I expect that overall activity in the Atlantic may be around average.
ENSO Conditions: The consensus of the ENSO model guidance are forecasting neutral ENSO conditions for the 2018 Atlantic Hurricane Season. The European model is forecasting a weak El Nino to develop sometime this summer while the CFS model is forecasting neutral ENSO conditions to prevail right through the end of this year. The overall weather pattern across North America continues to exhibit a La Nina like look and I think it will take some time for conditions to transition into a El Nino one and any El Nino weather pattern will probably be delayed until this autumn at the earliest.
It should be noted that the European model, which is currently forecasting weak El Nino conditions to form this summer, has a high bias with forecasting ENSO. Last year, this model forecasted a moderate to strong El Nino and in the end this El Nino never developed. On the other hand, the CFS model which was forecasting borderline La Nina conditions seems to be trending towards a neutral ENSO summer and autumn.
Bottom line is that I do not think we will see the development of El Nino conditions anytime soon. I think instead we could see neutral ENSO conditions prevail right through this summer with possibly weak El Nino conditions developing sometime between September and November. It is unlikely that we will see a third consecutive year of La Nina conditions, however, it is something that also cannot be completely ruled out.
Sea Surface Temperatures: Sea surface temperatures across the eastern Atlantic are slightly cooler than average while sea surface temperatures across the western Atlantic are slightly above average. Strong easterly winds during January and February caused the ocean waters across the tropical Atlantic to cool. During March, however, those easterly trade winds have decreased leading to the tropical Atlantic to warm back up to near average levels. How much the tropical Atlantic warms up during April and May will be a factor in determining how active the eastern and central Atlantic is during this upcoming hurricane season. It should be noted that at this time in 2017, the Atlantic Main Development Region was running a little below average in sea surface temperatures, but this pattern quickly reversed in April and hurricane season forecast numbers were sharply adjusted upward due to this quick warmup.
I think that it is likely that the area between the coast of Africa and the Lesser Antilles will feature slightly above average sea surface temperatures during July, August and September. With that said, I think that it is unlikely that this region of the Atlantic will be as warm or as active as it was during 2017.
Further west, the ocean water temperatures across the Caribbean and the western Atlantic continue to be above average and this could potentially mean that we could see tropical systems form close to the US coastline and the Bahamas.
Atlantic Multi-Decadal Oscillation: The AMO (Atlantic Multi-decadal Oscillation) is basically whether or not the Atlantic Basin SST’s and anomalies are above average or below average based on climatology. Currently, the AMO is in a weak positive state. This means SST anomalies continue to be warmer than the average, based on climatology. A positive AMO is conducive for an above average season, when coupled with other positive factors.
Wind Shear Forecast: A majority of the seasonal model guidance are forecasting near average or slightly below average wind shear across a majority of the Atlantic during the Hurricane Season. This could mean that overall environmental conditions may be favorable for tropical development this season.
Potential Weather Patterns: The combination of a positive Atlantic Multi-Decadal Oscillation signal, neutral ENSO condition, a positive North Atlantic Oscillation, above average ocean water temperatures along the US East Coast will (1) Extend an area of high pressure near Newfoundland further to the southwest; (2) Produce a weaker trough of low pressure over the central Atlantic and (3) Shift a ridge of high pressure over the western Atlantic further to the northeast. In addition, we are forecasting a mean trough of low pressure to set up over the Ohio Valley this season.
All of this has the potential to delay the development of any storms until they are west of 50-60 West Longitude. In addition, any storms passing near the United States would be delayed from turning to the north and northeast. This would mean a high threat to the Bahamas, the US East Coast and the eastern Gulf of Mexico.
Risk Areas: The geographic area I am most concerned about for the 2018 Atlantic Hurricane Season is the area from the Carolinas northward to southern New England & Long Island, New York as well as for the Bahamas.
The Carolinas, Mid-Atlantic States, Long Island & Southern New England: Given our forecast of a mean trough of low pressure that is expected to be anchored over the Ohio Valley this summer into this autumn, we are quite concerned about a scenario of a tropical storm or hurricane being guided right up the US East Coast leading to impacts from the Carolinas to New England. In addition, all of the analog data which compares the current weather pattern to those from the past points to a significant threat to the area from North Carolina to southern New England.
Florida, Georgia & The Eastern & Northeastern US Gulf Coast: A slight shift in the upper air pattern this season towards one that features the mean trough across the Midwestern United States could put the eastern Gulf Coast and Florida at significant risk from a tropical storm or hurricane. This threat area includes the Alabama coast, the Florida Panhandle, the entire Florida Peninsula and southern Georgia.
The Western Gulf Coast has some risk from a tropical storm or hurricane impact this year with the highest risk of this occurring during June or July. Overall though, I think the higher risk in the Gulf of Mexico will be across the eastern Gulf of Mexico rather than the western Gulf of Mexico.
The Central & Eastern Atlantic from the Lesser Antilles to the coast of Africa could end up being less active than it was during 2017. The ocean water temperatures are currently below average from 45 West Longitude eastward to the coast of Africa. It should be noted though that ocean water temperatures near the Lesser Antilles are above average and we are going to have to watch for any tropical disturbances strengthening suddenly as they approach the Lesser Antilles this season.
The Caribbean is an area that could be inactive this season due to above average wind shear and below average temperatures. The exception may be across the far eastern Caribbean, including the Lesser Antilles, Virgin Islands and Puerto Rico as above tropical systems may strengthen suddenly in this area due to above average ocean water temperatures and a forecast of below average wind shear.
All-in-all, the area of main concern this season for impacts from tropical storms/hurricanes may end up being the Bahamas and the area from the Carolinas northward through the Mid-Atlantic States to Southern New England. With that said, there is also a significant threat for Florida and the eastern Gulf Coast from a tropical storm/hurricane threat.
2018 Atlantic Tropical Cyclone Names: