NOAA increases prediction for 2019 Atlantic hurricane season
MIAMI, Fla. - The National Hurricane Center, a division of the National Weather Service, has increased the likelihood of “above-normal” activity in the Atlantic Basin for the remainder of the 2019 hurricane season.
Their forecast update increased the probability of “above-normal” activity from 30% to 45%, including an increase in the amount of named storms (i.e. tropical storms) from 9-15, to 10-17 storms.
A normal Atlantic hurricane season consists of 12 named storms, 6 of which strengthen into hurricanes, 3 of those hurricanes reaching category 3 strength on the Saffir-Simpson scale.
To be clear, their forecasts are NOT landfall forecasts. Any seasonal landfall forecast you come across is very likely wrong. Their forecast only is to predict the number of storms with tropical storm force winds of 39 mph or greater, per season.
Up until the first week of August, there have only been three storms to reach tropical depression strength or greater. Two of those storms were named.
Sub-Tropical Storm Andrea around May 21, which impacted Bermuda.
Hurricane Barry around July 13, which impacted the Louisiana coast.
Tropical depression three around July 24, off the Florida/Georgia coast.
Atmospheric conditions have not been conducive for tropical development for majority of the 2019 season, which began June 1. This is expected to change, possibly quickly and abruptly.
Statistically, most hurricanes develop from August through October, not May through July..
On May 23, the National Hurricane Center issued its 2019 Atlantic hurricane forecast, predicting a “near-normal” amount of tropical cyclone activity this year due to a few key things:
The winter El-Nino pattern would remain persistent into the summer months. This tends to discourage tropical development, suppressing overall activity
Warmer than normal water temps would aid in tropical development. Would a storm develop, rapid development could be possible, as observed with Hurricanes Harvey (2017) and Michael (2018).
The west African monsoonal season would be stronger this year, leading to increased opportunities for low pressure waves to form in the Sahara desert, then migrate into the Atlantic Ocean. This would increase the frequency of tropical storm systems (on average, 2-3 per week)
The latter two encourage tropical development, whereas the El Nino pattern would discourage tropical development
On August 8, the National Hurricane Center issued its mid-season update, predicting an increase in overall tropical cyclone activity for the remainder of the 2019 season.
The reason: the forecasted end of the current El Nino pattern which lead to significant rains over the United States this past winter and spring. This has also been responsible for the lack of overall activity in the Atlantic Ocean and Caribbean.
Pictured in this article is a diagram illustrating typical development of tropical waves in ideal conditions, which originate from Africa’s Sahara desert.
Warm, dry areas of low pressure will organize over the warm waters of the Atlantic, creating thunderstorms. Assuming atmospheric conditions are perfect, the storm system will continue to organize and intensify until it turns into a counter-clockwise rotating cyclone, or hurricane if winds remain sustained at 74 MPH, or greater.
Often, this is not the case. Dry air aloft kills storms. Strong, or even moderate jet stream winds aloft kills storms. These storms like calm conditions. These storms prefer a “lazy river” type of jet stream.
With some limiting factors now trending out of the long-range pattern, an uptick in tropical cyclone activity is possible leading into the peak months of the season.
The Atlantic hurricane season lasts until November 31.