Thursday, July 1, 2010

Hurricane Alex Grades & More!

I'll first start with the grades and then go into some interesting forecasting tips with hurricanes...

Hurricane Alex

LONG RANGE TRACK: I rarely will do this, but I honestly give myself an A+ on this... 10 days before landfall I targeted southern Texas/northern Mexico... Of course there is always some luck involved, but I always felt from day one that the ridge would hold strong! The models, especially the GFS, wanted to break down that ridge way too fast... I have talked enough on why that typically doesn't happen, but you can always refer to older blog posts for much more information on why I knew the ridge would hold strong once again!

SHORT RANGE TRACK: I would give myself a solid A here as well... I had Brownsville, TX as the furthest north landfall spot, with northern Mexico as the likely target region for Alex... Again, it came down to the strength of the ridge, when as close as Monday a few of the models started to trend more north towards central/northern Texas... I always held strong on the westward track, as I knew the ridge once again would hold strong... Just consider for a second how incredibly hot it has been in the Deep South this June, so this wasn't some typical early summer ridge... The GFS already can't handle heat/heat transfer! So with all this extra heat in the atmosphere, how well do you think the GFS will do? I think Alex is a good example on why you can't trust the GFS to resolve heat/heat transfer issues 48 + hours out! Plus, I'll show you again in the future why the Asian trough/ridge pattern also helped in my westward assessment! Plus, you have a hurricane releasing latent heat into the atmosphere, which only pumps (strengthens) the ridge more!

INTENSITY: I said it would get to at least a solid Cat-2, which it did... I really thought it even had a chance at a weak Cat-3, which honestly it may have been! It hit a remote region where you are not going to get a lot of ground truth with regards to surface winds... The pressure was 947mb at landfall, which is only 1 mb shy of Hurricane Audrey (Cat-4) at landfall, which is the strongest June Atlantic basin hurricane on record! Again, I would give myself a solid A on this...

So overall, I would give myself an A+, A, and A... It's probably one of my better hurricane forecast I have put out! Now look, while I pride myself on working hard everyday on forecasting, there was of course some luck involved... It is the weather, and sometimes things don't go as planned... Plus, while these model biases/teleconnections hold a lot of weight, they don't always work out the way you think they will... Sometimes hurricanes make their own environment and do what they want... Or there could be some small feature no person, model, or teleconnection could have foreseen! I'm very proud/pleased with my Alex forecast, but of course I still have a LOT of room to grow... Like every forecaster, I'm wrong plenty! Meteorology is one of those fields you can study everyday for the rest of your life, and maybe understand 50% of what's going on! This is one of the main reasons why I love forecasting the weather! It's ever changing, and the challenge is something I love as a competitor! Keep in mind that I'm a huge competitor with myself, as I'm by far my hardest critic!

Now onto some interesting forecasting tips that I have talked about before in the past... I'll hit on them again since we just had a real life example yesterday, as Alex made landfall in northern Mexico... I'm going to keep this as simple as possible without getting into to much of he physics/dynamics behind it!

1) Hurricanes hitting at a perpendicular angle to the coast, can see an increase in surface wind speeds due to the pressure gradient tightening up! Obviously, a hurricane wants to stay over the warm waters as long as possible... This is especially apparent as the eye approaches the shore... The eye almost pulls back briefly (compresses), increasing the pressure gradient briefly as the hurricane makes landfall.... This pull back increases the pressure gradient, and therefore increases the surface wind speeds near the coastline... This is more of a factor when hitting higher terrain and is most pronounced when the hurricane is moving fast (really should say propagating)! In a sense think of a car wreck! Say the higher terrain represents a 18 wheeler... If it was sitting at a red light, the faster a car hits it, the more the impact to the car... Obviously the faster the car hits it, the more it will be crushed, especially when you hit something substantial like a 18 wheeler... So with the eye of a hurricane, the faster it hits the coast, in a sense, the more it will be "crushed", and the more you tighten that pressure gradient...

Think about why that makes sense for a second... Have you ever heard people talk about the 1938 Great New England Hurricane? I can't remember all the details off the top of my head, but basically you had a Category-3 hurricane moving (propagating) at 50mph... Many people say that you add that 50mph to the actual wind speeds within the hurricane... However, if you think about that for a second, it's bad physics! If you add 50mph to the NE quad, then why don't you subtract 50 mph from the NW quad? If you look at the wind reports from the 1938 hurricane, you will see that didn't happened (1944 great Atlantic hurricane is another good example of this)... Also, please remember that hurricanes don't move, they PROPAGATE! So I argue that the faster moving (propagating) 1938 hurricane, which hit at a perpendicular angle, was "crushed" into producing faster surface winds due to the extreme tightening of the pressure gradient at landfall... The Blue hill observatory in Massachusetts did have a 186 mph wind gust... You don't see that in a Cat-3, unless you have the frictional effects, compacting the eye, and increasing the pressure gradient... The 50mph was key, but not in the way most think!

2) An intensifying hurricane at landfall will cause more damage than a weakening storm at the same intensity, as it will more readily be able to mix stronger winds aloft to the surface, leading to more widespread verification of maximum wind speeds... It really makes sense if you think about it for a second... In a strengthening hurricanes the updrafts are growing in vertical extent, which again will help mix faster winds aloft to the surface... In a weakening hurricane the updrafts are decreasing in vertical extent, so you are not going to mix the faster winds aloft to the surface near as efficiently... Try to think in terms of a thunderstorm, but in the case of a hurricane, there are hundreds of thousands of them! This doesn't mean you can't get good wind gusts here and there with a weakening hurricane, but you will not see near the steady/faster winds verifying at the surface over a much widespread area...

Hurricane Katrina's first landfall in South Florida is a great example of this! A lot of people were shocked at how fast the surface wind speeds verified at, especially considering that Katrina was only a 80mph hurricane at landfall! Again, the strengthening storms can much more readily/efficiently mix down faster winds aloft to the surface... Personally from experience, I would be more worried about a rapidly strengthening Cat-2 like Alex, then a rapidly weakening Cat-3 like Dennis (2005)... At least from a wind perspective! Keep that in mind though, I am talking about the surface winds, not the surge... Storm surge is dependent of many more things than a just a strengthening vs. weakening aspect!

I know I'm not the only person that thinks this as well... Many hurricane chasers have seen this first hand... This was especially apparent to me and many other chasers in Hurricane Charley! Also with Charley, you didn't see it deteriorate near a fast, because again it was strengthening at landfall! You saw proof of this with 100mph wind reports in parts of central Florida like Orlando, and you saw it yesterday with Alex... It sustained its inner core much longer than a weakening storm at landfall would... Once again the speed of the hurricane plays a role in this as well! Obviously, the faster the hurricane moves (propagates), the more inland it will go while sustaining itself... This hopefully make a lot of sense, as the faster motion means more distance traveled when leaving the heat content (fuel) of the ocean! An intensifying, fast moving (propagating) hurricane can hold itself together for a fairly long time over land like we saw with Alex yesterday! It was pretty amazing to watch on satellite/radar imagery!

All of this is just things to think about, and I really hope it make some sense! I love trying to think things out in weather like a puzzle... Each piece helps you complete a picture of what's truly going on in the atmosphere... It's just like the model biases/errors... I'm able to piece things together to paint a fairly complete/accurate picture of what is really going on, because I understand how each piece relates to each other... Whether it's a teleconnection, a model bias, a forecasting tip, etc, all these pieces are unique and important! It's key as a forecaster to CORRECTLY piece everything you have together in a logical way if want to start painting the most complete/accurate picture of the atmosphere possible... Experience will lead you to more pieces of the puzzle and the ability to logically put them together, as you can't just force the pieces together! It may not always be perfectly clear, but I promise if you keep forecasting everyday, learning as much as you can, the picture you paint will be a lot clearer than most!


  1. This was a GREAT post, Greg! And good job - I think you deserve the grades you gave yourself. Interesting analysis at the end... and love the mention of NE Quad (haha) when referrig to the New England storm!

  2. Thanks Devin! It was nice to do well on the forecast! Trust me, I won't always do this well... Funny story with NE Quad... I came so close to naming my blog that a few years ago... I guess we think alike! haha... I'm glad you named your blog NE Quad though, you do a great job buddy! Keep it up!