Extreme Temperature Diary-September 27, 2018/ Topic: Rosa- Ominous Tumultuous Similarities To Florence And Harvey

Thursday September 27th… Dear Diary. The main purpose of this ongoing post will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials)😊.  Here is today’s main climate change related topic:

Rosa- Ominous Tumultuous Similarities To Florence And Harvey

I’d like to remind my readers that I am a meteorologist with 30+ years of experience forecasting weather, which was my bread and butter profession going all the way back to The Weather Channel’s inception during the early and mid 1980s. I’ve seen my share of wet weather patterns over the years, but what I’ve witnessed since creating this web site in early 2017 takes the proverbial cake. I really don’t like what I’m seeing on models in association with a new hurricane, Rosa, which is likely to make landfall in Baja California then deluge portions of the U.S. Southwest. Rosa is a weather event, so what will be any tie ins from this system to climate change? As the system traverses the United States what should we look for as far as attribution to carbon pollution goes?

First, what follows here in this post is a forecast, which I need to emphasize. At this point in time in my diary there are no guarantees that we will see locally heavy rain from Rosa in the Southwest or much wetness when the system is a post tropical low racing through the Midwest. The key word here is “racing.” It appears that Rosa will be a fast mover once it lifts out of the Southwest, getting picked up by the jet. Usually systems that are slow movers put down copious amounts of rain. Still, as we have seen in the last couple of years, it doesn’t take too long for even minor systems to produce flash floods, inundating areas not used to getting hit by walls of water with rainfall rates getting close to if not exceeding three inches per hour.

Yesterday I saw an AP article indicating that Harvey and Florence delivered the nation’s biggest one-two punch of flooding rainfall in United States history. Dr. Michael Mann replied to my associated note here (Please look at the two linked articles):

It is absolutely amazing to me that in the long history of the United Stares since colonial times in the 1700s that no place or area witnessed the top two rainfall events until 2017 and 2018. It appears that big storms are interacting also with an atmosphere charged with more moisture. Anyone familiar with the Clausius-Clapeyron Equation knows that at higher temperatures a parcel of air can hold more water vapor: http://www.science.uwaterloo.ca/~cchieh/cact/c123/clausius.html I think we are just beginning to reap the wrath sewn by heating up the planet via astounding inundations brought about by storms that in the past would be much less soaking. Others are taking notice on what the Southwest might see:

Definitely watching the heavy rain potential with or its remnants next week in the SW United States- notable upward trend in the forecast since yesterday.

 I’ve pointed out in prior posts that Florence and Harvey were affected by strong upper ridges becoming what my friend Edgar McGregor refers to as “lazycanes,” becoming nearly stationary over areas after landfall causing horrific inundation. Rosa will definitely not be a slow system, but it will enter an atmosphere in the U.S. charged with excess heat, being anomalously warm at upper levels across the eastern 2/3rds of the country:
          What makes a plague of locusts worse is a big supply of grain feeding a horde of insects. Likewise a relatively warm atmosphere holding more moisture is the recipe for any storm to feed off of, getting a chance to dump more rain or even snow than that of a colder, drier atmospheric counterpart. Rosa will get two chances to produce enough rain to be a big, pesky problem.
          First if, and I do mean if, the circulation of Rosa survives its interaction with colder Pacific water as it moves through part of the sparsely populated Baja Peninsula the system will probably dump heavy rainfall amounts on Arizona, including the deserts, and southern Rockies. The lower Rosa’s central pressure remains, the better chances for the system to dump heavy rainfall. Here is one of the latest models depicting Rosa moving into Arizona from Monday into Tuesday:
The second chance for flooding rain may come when Rosa as an extratropical low interacts with a front somewhere over the Midwest. As we know from meteorology 101 fronts squeeze moisture out of the air. Another clue that Rosa might be able to be linked with climate change is the heat itself forecast by models to be in the Plains south of the system. It looks like we may see near record heat south of Rosa looking at the following forecast panel:
Too, don’t be surprised if Rosa and the front become responsible for severe weather in the Upper Midwest, as well. Scott Cook has created a model loop depicting rainfall amounts that the GFS forecasts:

Here is another loop of Rosa potentially traversing the U.S. heartland:

My eyebrows are definitely raised from what I am seeing on the models in association with Rosa. I’m hoping that I can point back to this post in the next few days and say that any ominous prediction for Rosa did not materialise. We will see.


(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity.)

Here is some other weather and climate news from today:

‘s heaviest rains will arrive in the Windward Islands into the overnight hours even as Kirk’s center moves into the Caribbean. Forecast:

The aftermath of hurricane : polluted coastal waters with inky runoff–filled with “soils, sediments, decaying leaves, pollution, and other debris”.


I have seen one report of ETs from a hot Florida this evening:

Happy HOT Thursday! We set a record warm low temperature at RSMAS today (84°… the previous record was 82.6° set in 2000).  Also, Miami Int’l set a record warm low at 82° today (previous record was 81° set in 1989).

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The Climate Guy

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