CSU and TSR continue to predict a near-average hurricane season

By: Dr. Jeff Masters , 3:18 PM GMT on August 04, 2009

Share this Blog
1
+

A tropical disturbance embedded in the Intertropical Convergence Zone (ITCZ), near 9N 35W, is moving west at about 15 mph. The heavy thunderstorm activity associated with this tropical wave has changed little over the past 24 hours, and remains disorganized. This morning's QuikSCAT pass showed a moderate wind shift, but nothing resembling an organized surface circulation. Top winds were in the 20 - 30 mph range. Strong easterly winds are creating about 20 knots of wind shear over the wave, which is marginally conducive for development. The disturbance is about 300 miles south of the Saharan Air Layer (SAL), so dust and dry air should not hinder development over the next few days.

Given the disturbance's current lack of organization, combined with the presence of 20 knots of wind shear, any development should be slow to occur. The forecast wind shear along the storm's path over the next five days is predicted to remain at or below 20 knots, which should allow some slow development. Sea surface temperatures (SSTs) will warm from about 28°C to 29°C as the storm progresses westward. The GFS model has been indicating some development is possible in several of its runs over the past few days, but has not been consistent with this prediction. None of the other models show any development of the system. NHC is giving the disturbance a low (less than 30% chance) of developing into a tropical depression over the next two days, which is a good forecast. The GFS and ECMWF models predict the system will be approaching the northern Lesser Antilles Islands by Sunday. Both models forecast the development of a band of very high wind shear just to the north of the islands at that time, so the long-range survival of anything that might manage to develop is in doubt.

CSU forecast team continues to predict an average hurricane season
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued August 4 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 10 named storms, 4 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 83% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their June forecast, which called for 11 named storms, 5 hurricanes, and 2 intense hurricanes. Their April forecast called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (27% chance, 31% chance is average) and the Gulf Coast (26% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane (37%; 42% is average).

The forecasters noted that while sea surface temperature anomalies have increased in the tropical Atlantic and surface pressures have fallen in recent weeks, which normally would favor higher hurricane activity, the presence of El Niño conditions in the Eastern Pacific should counteract these influences. They forecast that the current weak El Niño event will strengthen to a moderate event by September:

El Niño events tend to be associated with increased levels of vertical wind shear and decreased levels of Atlantic hurricane activity. Tropical Atlantic sea surface temperatures anomalies have warmed somewhat since our early June prediction and surface pressures have fallen somewhat. But, the negative influences of El Niño-induced strong Caribbean Basin and Main Development Region vertical wind shear typically dominate over surface pressure and sea surface temperature in the tropical Atlantic.



Figure 1. Change in Sea Surface Temperature anomaly (in °C) between July 2009 and May 2009. Most of the tropical Atlantic has warmed, relative to normal, over the past 2 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: weak to moderate El Niño conditions, and average tropical Atlantic and far northern Atlantic SSTs. Those four years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 1965, which had Category 3 Betsy that hit New Orleans; 1963, which had Category 4 Hurricane Flora that devastated Cuba; and 1957, which didn't have any hurricanes that hit hit land during the peak part of hurricane season. The mean activity for these four years was 9 named storms, 4 hurricanes, and 2 intense hurricanes--almost the same as the 2009 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team have historically offered a skill of 45 -62% higher than a "no-skill" forecast using climatology (Figure 2). However, they are using a new forecast scheme this year, so it is difficult to judge how skillful this year's forecast might be.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

August 2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) also issued a new forecast today, and have increased their numbers by 20% from their June and July forecasts. TSR is also calling for a near-average season, predicting 12.6 named storms, 6.5 hurricanes, 2.8 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 103% of average. Their June forecast called for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are slightly above the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TSR predicts a 40% chance of an above-average season, 44% chance of a near-average season, and a 19% chance of a below-average season, as defined by ACE index. TSR rates their skill level as 51% above chance at forecasting the number of named storms, 60% skill for hurricanes, and 44% skill for intense hurricanes. These are far higher skill numbers than the June ones: 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.8 named storms will hit the U.S., with 1.6 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these August forecasts for U.S. landfalls is 25% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.1 named storms, 0.5 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their increased forecast: higher sea surface temperatures than expected over the tropical Atlantic, due to the fact that the trade winds over the Atlantic should be slower than originally anticipated. Faster than average trade winds create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling.

The CSU and TSR groups are done making forecasts for the coming hurricane season, but NOAA is still due to put out an August update.

I'll have an update on Wednesday.
Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

Sign In or Register Sign In or Register

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 272 - 222

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30Blog Index

Quoting StormW:
250. cg2916 2:51 PM EDT on August 04, 2009
Quoting Weather456:


I'm all for the disagreeing. But I'm actually afraid of disagreeing with one person here. I don't want to get insulted.

Me too.


I'm not.

I meant I was for some disagreeing, so that we can see different viewpoints, and so the blog wouuldn't be boring.
Member Since: Posts: Comments:
Quoting tropicfreak:


I think you mean felicia. Enrique has onlt y 50 mph winds . Felicia has 70, almost hurricane-strength.
Actually Enrique has 60mph winds :D

Link
Member Since: Posts: Comments:
Hi there W456

For what it's worth I do see rotation out there but as most everyone on here knows that alone does not determine whether there is a potential cyclone in the making. In fact, we have all seen very strong waves that looked like tropical storms but did not have a closed low ( think Dolly ).

I am quite content to wait and see what it does. I don't care whether it looks good or bad or in between, it's just something to keep an eye on for now.
Member Since: Posts: Comments:
thingamabob: between a trough and a wave
Member Since: Posts: Comments:
Quoting Drakoen:
Firing in all cylinders!!! LMFAO! Please.


Drak, you are a very good forecaster, and have contributed to some very nice forecasts on the blog. However, with all due respect, your attitude lately is not very becoming of you. There are more tactful ways to disagree. You wouldn't want to lose your credibility on the blog - especially with some of the more experienced forecasters on here.
Member Since: Posts: Comments:
266. CUBWF
Weather456, I'm with you. There is no way you and Drakoen have any interaction, without get involved in trouble. That is always the end. Just try not get into nothing with him, and viceversa. Is going to be the best for both, and even more, for all the bloggers. Just my opinion.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting Magical:
Ok. Someone help me. How can so many people, experienced in this field or not look at the same thing and see something so different. I have been lurking here a few years now and just don't get the wishcasting/downcasting. Nothing any of you say will change natures course!

For those of you who wish for storms you obviously have never had your life changed by the ravages of mother nature. It is paramount to wishing for a tornado just so you can see one or track one. The people who loose homes, property, and life are changed forever.

So I appreciate those here that give us useful, purposeful information, but for those who just throw out wishes....please...think before you do that.

Storm W. Thank you for the information backed by science.


Tropical forecasting and analyzing a satellite loop is something that requires congnitive processes, and is therefore influenced by personal viewpoints. For some people, they have a preconception before a storm forms that nothing will happen, therefore their mind is already leaning towards nothing when analyzing. And the same thing happens for wishcasters, there is already a bias present. For those people to admit that what they don't want to see happen is actually happening, there needs to be irrefutable proof.

Drak, while your forecasting is sometimes insightful, and you are also sometimes correct, there are times you (and everyone else on the blog) is incorrect. It is far from an exact science, and I applaud you for sticking to your guns. What I personally don't like seeing is you being somewhat rude in dismissing others opinions, and missing out on the objectivity side of forecasting.

A true forecaster doesn't care if a storm forms... they are more concerned about being as correct as possible.
Member Since: Posts: Comments:
Quoting Claudette1234:
looks like Enrique is making an eye?


I think you mean felicia. Enrique has only 50 mph winds . Felicia has 70, almost hurricane-strength. But you can spot enrique forming somewhat of an eye.
Member Since: Posts: Comments:
Back to the Pacific for a minute, I'm surprised we don't have a Fujiwhara. I mean, they're close (much closer than 98L and 97L), and moving in the same direction.
Member Since: Posts: Comments:
Quoting CUBWF:
Hi IKE, as always since the begining of this blog you have been one of the most respectull people here, even if you disagree. Sometimes youngest may take that as an advise, like Storm and others. I think this wave has some chance but has to be, wait and see.


I may not have seen this right, but did you just call StormW a young kid?
looks like Enrique is making an eye?
Member Since: July 21, 2009 Posts: 0 Comments: 552
I think it may be trying to seperate from the ITCZ now looking at the loop.
Member Since: Posts: Comments:
Quoting BobinTampa:
FYI: If everyone agreed about where a storm was going/forming/poofing, this blog would be a pretty boring place.

If all the forecasters at the NHC had a blog like this, I'd bet it would look very similar to the discussions on here. Bottom line, reasonable, intelligent, informed people can interpret data differently.



The respectful part is up for debate at times on here

Quoting kmanislander:
Good afternoon.

I see that we are in the " spin/no spin zone ". Where I have I heard that before LOL

But seriously though, the only thing that seems for sure is that given the current state of organization the thingamabob out in the Atlantic will not be following the track forecasted by the models yesterday.

West bound IMO.
Thingamabob is the best description all day!
Member Since: Posts: Comments:
Morakot is sparking this map. :D
Member Since: Posts: Comments:
Quoting tennisgirl08:


Based on that image - definitely no spinning!! LOL - j/k

456...looks to me like the convection is getting more confined to the center. Looks very well-structured. Thoughts?


yea it seems to be transitioning, we'll have to see.

hellow kman.
Member Since: Posts: Comments:
Quoting mobilegirl81:
No t an Ivan, but tracking as low as him.


I agree. brought up that same point in a couple posts yesterday.
Member Since: Posts: Comments:
Quoting Weather456:


I'm all for the disagreeing. But I'm actually afraid of disagreeing with one person here. I don't want to get insulted.

Me too.
Member Since: Posts: Comments:
Quoting Claudette1234:
Impresive



Do you guys notice that these storms are trying to form an eye?
Member Since: Posts: Comments:
in my experience an awful lot of tropical storms look like crap in their lifetime, especially in their genesis
Member Since: Posts: Comments:
247. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Warning #13
SEVERE TROPICAL STORM MORAKOT (T0908)
3:00 AM JST August 5 2009
=========================================

Subject: Category Two Typhoon In Sea South of Japan

At 18:00 PM UTC, Severe Tropical Storm Morakot (980 hPa) located at 22.5N 133.6E has 10 minute sustained winds of 50 knots with gusts of 70 knots. The storm is reported as west at 9 knots

RSMC Dvorak Intensity: T3.5

Gale-force Winds
================
450 NM from the center in the southern quadrant
200 NM from the center in the northern quadrant

Forecast and Intensity
=========================
24 HRS: 23.5N 130.4E - 55 knots (CAT 2/Severe Tropical Storm)
48 HRS: 24.8N 126.9E - 60 knots (CAT 2/Severe Tropical Storm)
72 HRS: 26.5N 123.2E - 65 knots (CAT 3/Typhoon)
Member Since: Posts: Comments:
No t an Ivan, but tracking as low as him.
Member Since: Posts: Comments:
Quoting tennisgirl08:


Based on that image - definitely no spinning!! LOL - j/k

456...looks to me like the convection is getting more confined to the center. Looks very well-structured. Thoughts?


I agree with you 100%.
Member Since: Posts: Comments:
Quoting Claudette1234:
Impresive


Very.
Member Since: Posts: Comments:
FYI: If everyone agreed about where a storm was going/forming/poofing, this blog would be a pretty boring place.

If all the forecasters at the NHC had a blog like this, I'd bet it would look very similar to the discussions on here. Bottom line, reasonable, intelligent, informed people can interpret data differently.

Member Since: Posts: Comments:
Quoting CUBWF:
Good afternoon everyone. The calm before the storm, and it's not in the Atlantic. Disagree is good, it bring better results, but respect each other, even if we don't care others opinions. In this stage, the center can be pinpoint until it really make it.


I'm all for the disagreeing. But I'm actually afraid of disagreeing with one person here. I don't want to get insulted.
Member Since: Posts: Comments:
Impresive

Member Since: July 21, 2009 Posts: 0 Comments: 552
240. CUBWF
Hi IKE, as always since the begining of this blog you have been one of the most respectull people here, even if you disagree. Sometimes youngest may take that as an advise, like Storm and others. I think this wave has some chance but has to be, wait and see.
Member Since: Posts: Comments:
Quoting cg2916:

I don't know. There's a front extending down, maybe they think something will break off the front.
True because they've had the area of purple off the coast...but why that far north I don't know either...
Member Since: Posts: Comments:
Quoting kmanislander:
Good afternoon.

I see that we are in the " spin/no spin zone ". Where I have I heard that before LOL

But seriously though, the only thing that seems for sure is that given the current state of organization the thingamabob out in the Atlantic will not be following the track forecasted by the models yesterday.

West bound IMO.

No spin zone... oh no! I don't want Bill O'reilly on this blog.
Member Since: Posts: Comments:
Quoting BurnedAfterPosting:


system is in the CATL now, updates much more frequently


Yeah. I was looking at Africa but I agree on the updates, they went 12 hrs this last time.
Member Since: August 18, 2008 Posts: 0 Comments: 628
Good afternoon.

I see that we are in the " spin/no spin zone ". Where I have I heard that before LOL

But seriously though, the only thing that seems for sure is that given the current state of organization the thingamabob out in the Atlantic will not be following the track forecasted by the models yesterday.

West bound IMO.
Member Since: Posts: Comments:
Quoting Chicklit:

Disorganized mess it may be, but it's not going away.


I wouldn't say a mess, some bands are forming. But it does look somewhat disorganized. Most of the strongest convection is near the supposed center of the disturbance. There is some circulation.
Member Since: Posts: Comments:
Quoting StormW:


That's true...100%...but when we put out information, let's try to be as accurate as possible. Saying there isn't much spin, when you can see rotation as plain as day, is not accurate.


Very weak and ill-defined embedded within the ITCZ and the extent of the surface trough axis is.
Member Since: October 28, 2006 Posts: 57 Comments: 31658
Quoting weatherwatcher12:


Based on that image - definitely no spinning!! LOL - j/k

456...looks to me like the convection is getting more confined to the center. Looks very well-structured. Thoughts?
Member Since: Posts: Comments:
Quoting weatherwatcher12:

Looks like rotation, and I can make out a center.
Member Since: Posts: Comments:
Firing in all cylinders!!! LMFAO! Please.
Member Since: October 28, 2006 Posts: 57 Comments: 31658
Quoting cyclonekid:
No more Green....can anybody tell me why the strip of purple is out like E of the Chessapeake Bay?

I don't know. There's a front extending down, maybe they think something will break off the front.
Member Since: Posts: Comments:
229. N3EG
Quoting cyclonekid:
you're right...even I could see the rotation...as a matter of fact...are there 2 areas of rotation?


Hey, even in a still picture, I can see some rotation. Or maybe I've just had too much to drink. I don't know.
Member Since: Posts: Comments:
Member Since: May 16, 2009 Posts: 1 Comments: 1231
How does the fact that this system is staying below 10N affect the future trajectory? Is there any possibility of it making it into the Carribean?
Member Since: Posts: Comments:
Quoting cyclonekid:
Looks like TD 2 in the making. :S

what the hell it is TD 2 in the making
Member Since: Posts: Comments:
225. IKE
Quoting CUBWF:
Good afternoon everyone. The calm before the storm, and it's not in the Atlantic. Disagree is good, it bring better results, but respect each other, even if we don't care others opinions. In this stage, the center can be pinpoint until it really make it.


Exactly. I've NEVER told anyone on here they should go on.
Member Since: Posts: Comments:
Ok. Someone help me. How can so many people, experienced in this field or not look at the same thing and see something so different. I have been lurking here a few years now and just don't get the wishcasting/downcasting. Nothing any of you say will change natures course!

For those of you who wish for storms you obviously have never had your life changed by the ravages of mother nature. It is paramount to wishing for a tornado just so you can see one or track one. The people who loose homes, property, and life are changed forever.

So I appreciate those here that give us useful, purposeful information, but for those who just throw out wishes....please...think before you do that.

Storm W. Thank you for the information backed by science.
Member Since: Posts: Comments:
No more Green....can anybody tell me why the strip of purple is out like E of the Chessapeake Bay?
Member Since: Posts: Comments:

Quoting cg2916:
It looks like the wave is losing convection.


yep its near D-Min over there
Member Since: Posts: Comments:

Viewing: 272 - 222

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30Blog Index

Top of Page

About

Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

JeffMasters's Recent Photos

Dunham Lake Sunset
Carrot Nose in Danger
Deep Snow in Brookline, MA
Sunset at Fort DeSoto