Welcome back to The Eyewall! We’re going to fire back up some regular updates now as hurricane season approaches. The plan is currently to post an update each Monday, Wednesday, and Saturday until activity necessitates more frequent posts.
Headlines
GFS model periodically trying to spin something up around Memorial Day in the SW Atlantic or Caribbean.
While that may or may not happen, it’s about this time of year that the GFS model tends to do some wild things that are usually unrealistic so use it carefully.
Eastern Pacific may kick up some activity later next week.
Checking in on the tropics: A reminder about the GFS model
Over the last week or so, we’ve started to see some signs in weather models of some very late period mischief in the Caribbean. This is especially true on the GFS operational model. For those of you that track these things, it’s around this time of year that the GFS begins to go a little haywire with tropical activity traditionally. For whatever reason, it likes to latch onto potential tropical disturbances and blow them up into well-organized storms, usually in the Gulf or Caribbean in May and early June. As most of you know, the chances of a very well-organized May or early June storm is extremely low. So we always tell people to generally put little stock in the GFS operational model this time of year in the tropics.
Saturday morning’s GFS operational model was one of the runs that showed a developing organized system in the Bahamas near Memorial Day. (Tropical Tidbits)
Remember, operational models are known as “deterministic” models. They’re one run, one solution. As meteorologists, we have learned to use an ensemble approach to forecasting, particularly when trying to determine if tropical development is realistic in a medium-range to extended range timeframe. Ensembles are where they run these models anywhere from 30 to 50 or so different times. Each time, something is tweaked in the initialization (what the model is seeing at hour 0), and then the model is run out 240 to 384 hours. This allows us to capture a more realistic envelope of outcomes from the modeling that informs our thoughts on development, risks, etc.
Anyway, the thought process right now is that conditions may become slightly favorable in the Caribbean or Southwest Atlantic for something in about 10 to 15 days. But I would encourage a lot of caution about getting worked up regarding some of the GFS model runs. They may begin to show some outcomes that are unrealistic.
In the meantime, keep an eye on the Eastern Pacific. It may be time to fire up that basin in about seven to ten days. We’ll take another look at things on Wednesday.
May the 1st be with you. Today, we just want to briefly acquaint folks with some of the changes to expect in the upcoming hurricane season. Every year, lessons are learned, data is collected, and changes are implemented. Forecasters and those that communicate the risks and impacts are always attempting to improve, even if just a little.
The cone: New graphics available
The biggest and most important change this year from the National Hurricane Center will come via the cone graphic you often see.
Example of the old forecast cone graphic with warnings and watches from Hurricane Idalia last year. (NOAA NHC)
In the older maps, the watches and warnings covered the coastal regions, and that was that. As we’ve learned, impacts extend far from the track of the center and far from the coast very often. Thus, to capture this more, the NHC will now be including a different map, with the inland watches and warnings included.
An example of what the new cone graphics will look like later this season, which includes inland watches and warnings in the U.S. (NOAA NHC)
These watches and warnings have been issued for a number of years, but they’ve never been combined with the forecast cone on the NHC maps. These maps are considered “experimental,” which in NWS parlance means they may not always be available quickly. But they will be there, likely beginning in August. People will be able to provide feedback to the NHC about these images. We plan to include them when available in our posts.
The rainfall forecast: Going global, sort of
One thing I actually made mention of last year either here or on social media was the lack of rainfall forecasts for international locations. That will be partially corrected this season. Experimental rainfall graphics will now be issued by the NHC and Weather Prediction Center for the Caribbean and Central America. This is very good news, as rainfall is sometimes the biggest threat from these storms.
Experimental rainfall forecast maps will be issued for storms that impact the Caribbean and Central America this year, in addition to those that impact the U.S. (NOAA NHC)
This will give us another useful communication tool for individual storms.
U.S. watches and warnings: More frequent updates
In the past, NHC advisories could generally be broken into two groups: Primary advisories issued at 5 & 11 AM/PM EDT, and then intermediate advisories issued every three hours in between the two primary advisories. Very little would change in the intermediate advisories, other than position and intensity. Well, now the NHC will have the option to expand or trim back watches and warnings in these advisories for the U.S. So, if the forecast looks to change or the storm speeds up or something, there will be the option to give an additional 3 hours of lead time on watches or warnings. Every hour counts ahead of these storms, so this is a welcome change.
Other notes: Spanish, size, names
In addition to the big changes noted above, the NHC will implement some other tweaks this year. There will be additional products available this year in Spanish which should allow almost all key information to be accessed from the NHC in both English and Spanish. This is thanks in part to AI, which is really helping improve how much and how quickly information can be translated. I assume additional languages will be on the board in the future too.
Size forecasts for wind radii will extend out to days 4 and 5, previously only available through day three. The size of the cone is adjusted each year based on average track error. As the NHC states, “the size of each circle is set so that two-thirds of historical official forecast errors over the previous five years (2019-2023) fall within the circle.” It’s a little complicated, but it’s built to account for as much potential error as possible. This year’s cone size will actually increase a little in the Atlantic basin, particularly in days 3 through 5, though not by a huge amount.
Hurricane season outlooks continue to populate, and according to the Barcelona Supercomputing Center site that tracks these things, the current consensus forecast for the 2024 season is 23 named storms, 11 hurricanes, and 5 major hurricanes, compared to an average of 14, 7, and 3 respectively. So, yes, this season is highly likely to be very active. We’ll have more for you soon, and we’ll start pushing daily outlooks out sometime later this month. Spread the word on our site, and follow us on the socials.
Recent rainfall and flooding in Dubai of all places has set off a firestorm of misleading, incomplete, and even some bizarre theories on social media. How did this actually happen? Turns out it was a pretty straightforward forecast, and no one should be surprised that this was a major event. It just happened to also hit a place that has a lot of people, rarely sees events of this magnitude, and happened to mention that they also seed clouds, which is unlikely to have done much to affect the outcome.
Headlines
Dubai was recently hit with a storm that dumped copious amounts of rain on the desert megacity, arguably their heaviest rainfall since at least the 1950s.
Over 6 inches of rain fell in 24 hours, which equates to over 2 years of average rainfall for Dubai.
Dubai captured the headlines, but the rain also impacted places like Oman, Bahrain, Saudi Arabia, and Qatar.
The event was extremely well-forecast and captured by modeling ahead of time.
Cloud seeding likely contributed a little to rain totals, but should not be attributed as the cause of the flooding.
What happened?
An extremely anomalous weather pattern established over portions of the Persian Gulf and Middle East this week, featuring a rather deep upper-level trough over the area. This type of pattern is what typically brings unsettled, wet weather to mid-latitude locations.
A deep upper-level storm arrived and slowly migrated eastward across the Arabian Peninsula between Sunday and Wednesday. (Tropical Tidbits)
This trough seems to be cut off from the jet stream, a condition that also isn’t necessarily uncommon in many places, and historically it does lead to localized prodigious precipitation totals in spots under the right conditions. So while the placement of this weather system was a little strange, the outcome (scattered heavy rain and flooding) was not.
Forecast rainfall from the ECMWF model’s Sunday overnight run showed as much as 5 to 6 inches of forecast rainfall over the Strait of Hormuz, the north tip of the UAE, and portions of Oman and Iran. (Tropical Tidbits)
Model forecasts were all over this. In fact, the forecast from Sunday’s European model (shown above) pegged Dubai for roughly 4 inches of rainfall between Sunday and Thursday, with most of it falling Tuesday. Nearby areas showed bullseyes of 5 to 6 inches of rain over the Strait of Hormuz and into portions of southeastern Iran, as well as in Oman (where over 15 people died from flooding). So this was not a surprise storm by any means. Unusual and historic, certainly, but not a surprise from a modeling standpoint. This is about as well telegraphed as you could hope for.
Various other factors likely helped amplify the rainfall over the UAE, Oman, and Iran. The location of this region in proximity to a number of features that usually align with heavy rainfall, and the presence of precipitable water values (PWAT) that were likely over 200 percent of normal made this basically a straightforward case of an area that would get hammered by heavy rain.
Precipitable water values were forecast to be over 1.25 to 1.5 inches above normal in portions of the Arabian Peninsula and southern Iran on Tuesday. (Pivotal Weather)
Precipitable water is essentially how much moisture is available for rainfall. If I saw this 2 to 3 days ahead of time over a place many of you will be more familiar with, like Houston, I would expect flood watches and warnings to be imminent.
The bottom line: An anomalous pattern produced an anomalous result, and nothing about it should have been a surprise given the forecast.
Did cloud seeding make it worse? Not really
If you read the above section, you can see that models were actually printing out 4 to 6 inches of rainfall over this area. Cloud seeding is a process where humans fly an aircraft into a storm and release a small amount of a harmless compound, typically silver iodide. The intent is to seed the storm with a few more nuclei for raindrops or snowflakes to form on within the cloud that will enhance precipitation downwind of the storm. This strategy has been practiced for years, all over the world, and almost always in arid areas where water is a vital and precious commodity. Every little bit helps these areas, so when storms happen, it is common for cloud seeding to occur. Typically, you could see rain totals increase by 5 to 15 percent based on the project. Each one has mixed results, some with more rain, some with little to no increase in rain.
So doing that back of the envelope math, if you assume the UAE generates cloud seeding results on par with historical averages, you would be looking at roughly 0.3 inches to 0.6 inches of additional rainfall. When dealing with 6 inches of rain in an arid location that lacks the ability to handle so much water, that’s primarily background noise, a rounding error mostly. Cloud seeding certainly did not cause the storm, as we saw above. And historical results suggest it would have had minimal impact on the end results as well, other than providing just a little more water for an arid region. It’s like saying that the 538th home run by an unnamed baseball player that allegedly took performance enhancing substances was directly caused by the performance enhancing substance. That ballplayer would almost certainly have hit a deep fly ball or even a home run without the PEDs, but the PEDs just added a little whipped cream on top to nudge it out. The heavy rainfall was the cake, the cloud seeding was the icing. You’re still getting cake, you’re just getting a few more calories.
What else should we know?
We’ve seen a lot of heavy precipitation extremes in recent years all over the world, and as much as many folks don’t want to discuss climate change, you absolutely need to in this instance. Here’s a look at Persian Gulf and Gulf of Oman water temperature anomalies.
Water temperatures are running substantially above normal in the Gulf of Oman, Persian Gulf, and Arabian Sea. (Weather Bell)
Given the Arabian Peninsula’s location, if you were to inject 200 percent of normal moisture to this area and got heavy rain, it was almost certainly influenced by the excessively warm Arabian Sea, Persian Gulf, and Gulf of Oman. No matter which direction the wind was coming from, you were probably transporting this warm, moisture-laden air into an already primed atmosphere. The end result was one of the worst rain events for an area in modern times. Our oceans are on fire around the world right now, and heavy precipitation extremes are increasing. The causes are more complex than a social media post or three could cover, but climate change is a significant player in it all. Expect to see more situations like this in the coming months and years.
Thanks to everyone who used our site in advance of Monday’s eclipse. Sunday was our highest traffic day since October. So we’re glad some of you sought us out or found us!
It’s now April 11th, which means the start of hurricane season is less than 2 months away. As we’ve discussed ad nauseum, it’s expected to be a very active season. With that in mind, barring a massive weather event between now and then, we’re going to take the foot off the gas a bit. We have a few things to address before the start of hurricane season, including changes to some of the tools and products this year, as well as the name list, among other things. We’ll push some posts out about that stuff over the next six weeks. You may have read about it elsewhere, but we intentionally opted to wait til we got closer to the season to discuss these things, when it becomes relevant.
In the meantime, please give us a follow on our primary social channels, feel free to subscribe to our emails (at right), and let us know if you have any questions:
Remember, our preparedness page has a ton of links to local sites that can help you with relevant, local information on getting ready ahead of hurricane season.
