- Category Archives Typhoon Rule
First and foremost, I’ll apologize in advance for a lack of posts today and go ahead and apologize for the same tomorrow. We’ve been incredibly busy over the past couple days and as a result posting has (and will be) out of schedule until mid week.
We wanted to briefly touch on early September with this post. (This isn’t our September forecast, as that will be posted by the end of the week).
Speaking of September, we’ve always had September as a warmer than normal month. Despite the warm September forecast, we did initially think we may have a 2-3 day period in early September that would feature yet another pop of cooler than normal air. That’s speaking specifically at the period around 9.3-9.5 (give or take a day or two) and after a warmer than normal stretch this weekend into early next week. (By the way, after a warm September, we think things turn cold rather fast in October and November, but that’s for another day).
The reasoning behind our thinking of a few days of cooler air in the 9.3-9.5 time frame was from the overall pattern that is leading to Typhoon Atsani recurving in the western north Pacific. It’s important to note that it isn’t the recurving typhoon itself, but the overall pattern that provides a good hint at what’s ahead downstream 6-10 days later- be it ridging or the tendency for “troughiness.”
However, modeling has been trending towards Atsani stalling in the north Pacific and even some data likes to drift the system northwest over time through the upcoming weekend before significant weakening.
The end result here? Much less emphasis on cool and attention that turns to a rather lengthy period of warmer than normal temperatures through the month of September, including early September.
*We’re going to begin posting a discussion going into more detail around the what and why of the seven day forecast in the mornings, followed by the actual updated 7-day in the evening/ night. We hope you enjoy!
The Monday morning satellite shows moisture streaming north. It’ll be a warm and humid day with scattered to numerous showers and thunderstorms developing, especially during the afternoon and evening hours.
Scattered to numerous storms:
The images above highlight the idea of widespread showers and embedded thunder expected this afternoon. As we say, it’s impossible to say for certain where the precise showers and storms will be on Futurecast products, but you can get an overall idea of storm coverage.
While everyone won’t get heavy rain, the high PWATs do suggest some localized torrential downpours are certainly possible.
We continue to keep a watchful eye on Wednesday for the potential of strong to severe thunderstorms during the afternoon and evening hours. An unusually strong trough (for August) will plow into a very warm and humid air mass and as the cold front moves through Wednesday PM, we’ll remain on our toes for strong to severe storm potential.
Double Shot of Cool Coming:
Once our cold front and associated severe weather maker slide east Wednesday night, MUCH cooler, drier air will arrive into the region. This was set up nicely 10, or so, days ago by our recurving WPAC typhoon.
Note the GFS ensembles showing another pop of cool coming next week.
With the typhoon activity and a deeply negative SOI, the long term continues to look active as we rumble into September. Recurving Typhoon Atsani would imply for another shot of unseasonable chill around the open to September.
Right off the bat, we tend to lean more in the direction of the 12z GFS and its’ associated cooler look next week, rather than the warm European. It’s a challenging pattern, no doubt, but the combination of two recurving typhoons in the western Pacific (WPAC) and the incredibly wet ground argue for a lack of any significant, or long lasting, heat.
After a cool July, a true push of summer heat and humidity will blow into town Friday, after a round of noisy thunderstorms during the predawn hours. Highs this weekend will zoom into the lower 90s (nothing unusual for late July), but couple that with lower to middle 70 dew points and you have the makings for oppressive and truly dangerous heat indices in the 100 degree to 105 degree range. Have weekend plans outdoors? Prepare to take frequent breaks and drink plenty of water!
That said, the weekend heat will get pushed back south as early as Monday as a cold front moves into the Mid West. Scattered thunderstorms over the weekend (especially during the prime time heating hours in the afternoon and evening) will grow in coverage and become widespread Monday. Locally heavy rain is possible.
Though admittedly a “challenging” pattern, we continue to think the recent wet ground (note 30 day rainfall totals below, courtesy of weatherbell.com) will make it incredibly tough for any sort of significant heat to hit and hold for any length of time over our region. – That’s not to say it can’t, and won’t, get plenty humid though (case in point this weekend).
We first learned of the “typhoon rule” from the great Weatherbell.com meteorologist Joe Bastardi years ago and were blessed with an opportunity to pick his brain further about this during a talk at Ball State a few years back. We’ve covered this in posts here previously, but the long and short of the typhoon rule is that when a western Pacific typhoon “recurves,” you can expect to see a downstream trough, and associated stormy/ cooler pattern, over the eastern portion of the United States 6-10 days later.
With that said, you can see why we’re skeptical of talk of long-lasting heat over the region over the next couple weeks. Much more later, friends!
There’s been a ton of conversation as of late about where this overall weather pattern is heading. Perhaps it’s the Christmas season that brings out the conversation as everyone is hoping for that cold pattern to provide a White Christmas.
While in the short-term cold will continue to dominate, we’re becoming increasingly confident of an unseasonably mild stretch of air in the mid-range period. That’ll take us up to the week before Christmas…
In the short-term, the positive PNA will continue to be the primary driver in our pattern. This will ensure a colder east through the majority of week 1 (through next Friday).
Modeling sees the cool east in week 1 and warm west- typical of a positive PNA pattern:
There are changes in the mid-range period that’ll have lovers of winter and cold frowning. Many of our long-term readers know how we use the “typhoon rule” as a good indication of what we can expect across our region 6-10 days down the road. As stated multiple times in the past (want to give credit where credit is due), we learned this from the great Joe Bastardi. For those that are new here, I’ll describe this very briefly (you can read through the archives, if you’d like, for a longer/ more detailed description). Typically when you have a recurving typhoon in the WPAC, that suggests a trough (colder pattern) across the central and eastern Lower 48. On the flip side, when you have a westward moving typhoon, that’s a good indication of eastern ridging (warmer pattern).
Courtesy of the Joint Typhoon Warning Center, Super Typhoon Hagupit is forecast to move on a general westward trajectory.
This is a very good sign of a much milder than normal period in the mid-range (days 8-12). Modeling, in return, is going towards a warm pattern (associated ridge) week 2:
The GFS ensembles and NAEFS agree on the warmth and given what we’ve discussed above, so do we:
In fact, it wouldn’t surprise us to see high temperatures in the 55-60 degree range during a day or two week 2.
Really quick and before we end- lovers of winter weather, there’s absolutely NO reason to throw in the towel. In fact, indications in the long range suggest the trough collapses into the east during the week leading up to Christmas and that could provide for all sorts of wintry “mischief” when almost all of folks are wanting snow…
Much more on that in the days ahead. Have a great night!
Perhaps you’ve heard folks discuss the “typhoon rule” over the past few weeks. What I despise is when people take credit for certain ideas without giving credit where credit is due. Joe Bastardi (Weatherbell Analytics) was the first that brought this to my attention.
I had the pleasure of hearing Mr. Bastardi speak at Ball State several years ago. (Quick side note- I thought this was open to the public, but upon arriving at the classroom, I believe I was the only one who wasn’t a current student at Ball State. Of course that didn’t deter me from playing the student role for a few hours to hear someone I respect a great deal practically right in my back yard). Anyway, it’s not the actual typhoon recurving that usually leads to a central and eastern US trough 6-10 days later, but, instead, the drivers behind what creates the western Pacific typhoon to recurve that leads to troughiness and associated cooler air downstream 6-10 days after the recurve.
The majority of mid to longer range forecast models continue to suggest October opens warmer than normal.
That said, note recurving Tropical Storm 16-W (image and forecast track courtesy of the Joint Typhoon Warning Center):
This would imply a central and eastern trough 6-10 days down the road (October 2nd-ish time frame), and obviously a much cooler look than what the data above implies.
Perhaps the European is beginning to catch on….
To summarize, despite what the majority of mid to long range guidance portrays as a warm October open, let’s keep an eye on that Oct. 1-5 time period for a possible cooler regime yet again. In the face of warm guidance, recurving Tropical Storm 16-W suggests we should monitor for a possible cooler trend in the guidance in the days ahead…