Weather, October 2021

Tropical Storm Rose 3

Tropical Storm Rose 3Sometimes we just need to laugh. Dealing with the global pandemic over the past year and a half has been tough on all of us. On top of this, the past two Atlantic hurricane seasons (this one is not quite over yet) have been extremely active and have resulted in significant property damage and destruction that has seriously impacted the lives of many people. Unfortunately, there have also been many injuries and fatalities associated with sone of these storms.

The forecasters at the U.S. National Hurricane Center have done a great job providing timely and accurate forecast information for the tropical storms and hurricanes over these past couple of years under very difficult circumstances. In addition to the increased tropical cyclone activity over this period, these forecasters have also had to adjust their workflows substantially due to the pandemic, in many cases working remotely to reduce the risk of becoming infected with or spreading Covid-19.

One of the products that the forecasters produce which offers great value to those who take the time to read them are the forecast discussions that are issued every six hours as part of the advisory package for each system. These discussions allow the forecaster to present information about the uncertainties in the forecast, to describe the different ways that each tropical cyclone could evolve based on the available data, and to go through the reasoning behind the official forecast and provide their confidence level in that forecast. I strongly recommend that anyone who is in a position to be impacted by a tropical depression, tropical storm, or hurricane read these discussions as they provide critical insight from the forecasters that can’t be gleaned from the official advisories, which focus only on the most likely evolution of each system.

Tropical Depression 17 formed in the eastern tropical Atlantic to the southwest of the Cabo Verde Islands on September 19, 2021. It was upgraded to a tropical storm and assigned the name Rose later that day. It peaked in intensity later in the day on September 20, 2021 with top sustained winds of 45 knots, then began to weaken and dropped back to tropical depression strength about 24 hours later. It lost its tropical characteristics early on September 23, 2021 and dissipated shortly thereafter.

Rose never affected land directly, and it never became a hurricane. It spent its entire life span in the eastern Atlantic, so it affected only shipping interests in that area, and perhaps some ocean voyagers who may have been in that region. It is safe to say that Rose will not be long remembered by most. Nevertheless, the forecasters at the U.S. National Hurricane Center fulfilled their responsibility to issue all of the advisory products for this system every six hours while it existed.

A couple of forecasters capitalized on this system’s name, which is the same as the well-known flower, to inject a little humor into their forecast discussions. So, without further ado, here are some excerpts from these discussions (emphasis on the funny phrases added):

From Discussion #6 issued at 1500 UTC 20 September 2021:

There are a lot of thorns in the way of Rose blossoming into a stronger storm.  Increasing shear and drier mid-level air are on the way for tonight, competing against the somewhat warm SSTs.  Thus Rose has about a day to flower into a moderate tropical storm, and no significant change was made to the short term forecast.  At longer range, stronger shear and dry air should pull the petals off Rose one-by-one, causing the cyclone to slowly weaken.  The new forecast is similar to the previous one, with some small 5-kt downward adjustments.  Rose could even shrivel up into a remnant low by day 5, but that’s not shown yet in the forecast. 

From Discussion #10 issued at 1500 UTC 21 September 2021:

The storm’s environment is no bed of roses during the next several days, with persistent moderate westerly or northwesterly shear, plentiful dry air aloft and only marginally warm waters.  Almost all of the guidance shows Rose decaying into a tropical depression this evening, and the new forecast is decreased from the previous one, especially in the near term. A continuation of this hostile environment should cause further weakening, and Rose is expected to be pushing up daisies in 3 days or less, degenerating into a weak remnant low and dissipating by the end of the forecast. 

From Discussion #11 issued at 2100 UTC 21 September 2021:

The cyclone has a difficult environment ahead, with persistent moderate westerly or northwesterly shear, plentiful dry air aloft and only marginally warm waters.  All of the guidance shows Rose decaying into a tropical depression fairly soon, and it could even wither into a remnant low tomorrow or Thursday in the harsh conditions.  However, the shear could let up just enough, along with some upper divergence from an upcoming trough interaction, to continue to produce deep convection for a few days.  This isn’t an easy forecast because some of the guidance actually re-intensifies Rose due to the trough, while other guidance completely dissipates the tropical cyclone.  Given the considerable uncertainty, I’ve kept the previous forecast the same at long range until more clarity emerges in the model suite.

From Discussion #17 issued at 0900 UTC 23 September 2021 (the final discussion for this system):

Rose has withered away.  The cyclone has not produced organized deep convection for nearly 24 hours now, and therefore, the system no longer meets the definition of a tropical cyclone. The initial intensity of the remnant low is held at 30 kt based on the earlier ASCAT data.

Clearly these forecast discussions conveyed needed information for anyone that might have been impacted by this system, but the forecasters were clever enough to add a little spice to them. I, for one, found these discussions to be a brief, but pleasant diversion.

Laughing is good for us once in a while, particularly during stressful times.

For those who would like to read the discussions in their entirety for this system (or any other system since 1998) use the following link: Click on the system of interest, then find the column labelled “Discussions”. There is a bar near the top of the page to move to the storms of a different year.

Ken McKinley is an ON contributing editor and is a weather router and owner of Locus Weather based in Camden, Maine.

By Ken McKinley