CSU leaves their hurricane forecast unchanged; 92L and Colin's remains worth watching

By: Dr. Jeff Masters , 2:38 PM GMT on August 04, 2010

Share this Blog
4
+

Tropical Storm Colin was ripped apart by wind shear yesterday, and the storm's remnants are passing just north of the northernmost Lesser Antilles Islands today. Most of the heaviest thunderstorms are passing north of the islands, as seen on Guadeloupe radar. Long range radar out of Puerto Rico also shows this. Colin's remains are in a rather unfavorable environment for re-development, since the disturbance is passing beneath an upper-level low pressure system with dry air and high wind shear. Wind shear is a high 20 - 25 knots over Colin's remains this morning. Recent satellite imagery shows that heavy thunderstorm activity has increased in intensity and areal coverage over the past few hours, though, and Colin's remnants will need to be monitored for re-development.

Forecast for Colin's remains
The latest SHIPS model forecast predicts that wind shear will drop from 15 - 25 knots today to a moderate 15 - 20 knots on Thursday. Wind shear will continue to decline over the weekend, and this relaxation of shear prompts most of the major models to predict re-development of Colin sometime in the next four days. NHC is giving Colin's remain a 20% chance of developing into a tropical depression by Friday morning. A major trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough will pull Colin to the northwest and cause it to slow down. By Friday, Colin will be moving at half of its current speed. All of the major forecast models are predicting that the trough of low pressure will be strong enough to fully recurve Colin out to sea early next week. Colin's remains may pass close to Bermuda on Saturday, with the latest 06Z (2am EDT) run of the GFDL model predicting that Bermuda will experience tropical storm force winds on Saturday as Colin passes to the west of the island. The Hurricane Hunters are scheduled to investigate Colin's remains at 8pm EDT tonight. It currently appears that Colin will only be a threat to Bermuda and Canada.


Figure 1. Morning satellite image of Colin's remains and Invest 92L.

92L
A tropical wave (Invest 92) in the south-central Caribbean is moving west at 15 - 20 mph. This wave is over warm water and is experiencing low wind shear of 5 - 10 knots, and could show some development over the next two days. However, the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, or the Yucatan Peninsula on Saturday, and 92L probably does not have enough time over water to develop into a tropical depression. NHC is giving a 20% chance of this disturbance developing into a tropical depression by Friday morning. This storm was being tagged as 98L yesterday; I'm not sure why it is being called 92L today.

CSU's forecast numbers for the coming hurricane season remain unchanged
A very active Atlantic hurricane season is on tap for 2010, according to the seasonal hurricane forecast issued today, August 4, by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team continues to call for 18 named storms, 10 hurricanes, 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) index 185% of average. These are the same numbers as their June 2 forecast. 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 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast continues to call for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (50% chance, 31% chance is average) and the Gulf Coast (49% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 64% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Moderate La Niña conditions should be present during the most active portion of this year's hurricane season (August - October). This should lead to reduced levels of vertical wind shear compared with what was witnessed in 2009.

2) Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season.

3) Very low sea level pressures prevailed during June and July over the tropical Atlantic. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80 - 85 percent of normalized hurricane damage.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this summer. Those four years were 2005, the worst hurricane season of all time; 1998, which featured 3 major hurricanes, including Category 5 Hurricane Mitch; 1952, a relatively average year that featured just 7 named storms, but 3 major hurricanes; and 1958, a severe season with 5 major hurricanes. The mean activity for these five years was 17 named storms, 11 hurricanes, and 5 intense hurricanes, almost the same as the 2010 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team over the past 12 years have had a skill 21% - 44% higher than a "no-skill" climatology forecast for number of named storms, hurricanes, intense hurricanes, and the ACE index (Figure 2). This is a good amount of skill for a seasonal forecast, and these August forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. This year's August forecast uses a new formula, so we don't have any history on how the technique has behaved in the past. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.61 to 0.65 for their previous August forecasts using different techniques, which is respectable.


Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. The British firm Tropical Storm Risk (TSR) will issue their outlook for the 2010 Atlantic hurricane season on June 4. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

The British private forecasting firm Tropical Storm Risk, Inc. (TSR) is scheduled to release their August forecast later today. NOAA will also be issuing their August forecast sometime in the next week.

This season has had three named storms so far (Alex, Bonnie, and Colin.) It will be difficult to have a season with 19 or more named storms, since the four seasons that had at least 19 named storms all had at least five named storms by this point (August 4.) These four seasons were 1887, 1933, 1995, and 2005.

Next update
I'll have an update on Thursday morning.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

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: 1062 - 1012

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 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56Blog Index

Quoting MiamiHurricanes09:
GFS 18z 48 hours, both the Euro and the GFS are in agreement that we will have Danielle in 48 hours.




wish storm lol
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Yep, they are currently our two best models, and when they come into agreement you know trouble is a lurkin'.


Hopefully that one will be an East Coast storm, since 04L looks to be a fish storm... :(
Member Since: Posts: Comments:
Quoting SeniorPoppy:


..Jaws music playing in background...




oh boy i did not no it iwas shark week
Member Since: Posts: Comments:
GFS 18z 48 hours, both the Euro and the GFS are in agreement that we will have Danielle in 48 hours.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
Yep, they are currently our two best models, and when they come into agreement you know trouble is a lurkin'.
just looking at the images of the wave near the cape verde looks like trouble its huge
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Yep, they are currently our two best models, and when they come into agreement you know trouble is a lurkin'.


..Jaws theme is playing in background...
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Link

This shows the low level circ center at around 19.7 N 65 W, hundreds of miles southwest of the main convection. Is there another circ center under the convection? Can't say, but if it's not obvious, it can't be strong.

If the convection to the NE takes over and becomes a storm, I think the trough will carry it out.

If the naked swirl NE of Puerto Rico can get some convection, could be a threat. But that naked swirl has a long, long, long way to go.

You are right I think that is actually the LLC remnants of Colin, I think the ball of convection was the around only area the HH flew today,I don't think they investigated 20N/65W, I could be absolutely 100% wrong, I think the area round 19.5/61.5W is the MLC that is working its way down to the surface and become the dominant one, the other is basically the old LLC swirl of Colin, jmo.
Member Since: Posts: Comments:
Quoting Drakoen:
With both the ECMWF and GFS showing development in the eastern Atlantic within 48 hours, the NHC needs to mention the disturbance SW of the CV islands.
Yep, they are currently our two best models, and when they come into agreement you know trouble is a lurkin'.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting will45:
fish dont live on land in Bermuda


as I said, some come on here just to get other peoples' reactions

we know that this is a threat to Bermuda and those who do not want to acknowledge that, well that is their choice
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Actually has the African wave as a TD there. Notice the closed isobar along with the wind barbs indicating a closed low. It also has ex-Colin as tropical storm Colin.


Yep. Two concurrent Tropical cyclones. I don't think that's happened at all so far this season.
Member Since: Posts: Comments:
1052. 7544
did he stall ?
Member Since: Posts: Comments:
Quoting hurricanehunter27:
Navy says Colin is a TS so i think when next rec flight goes out the will find that the COC is closed. Plus it looks quite impressive on the sat.
looking real good i expect a 40MPH TS at 11pm and the next TWo would likely say satellite images and surface observations from Hurricane hunter aircraft indicate that Colin has regenerate and advisories will be initiated shortly
Member Since: Posts: Comments:
Member Since: July 11, 2006 Posts: 14 Comments: 11173
1049. Drakoen
With both the ECMWF and GFS showing development in the eastern Atlantic within 48 hours, the NHC needs to mention the disturbance SW of the CV islands.
Member Since: Posts: Comments:
Quoting MahFL:
Colin is a fish storm......
fishcaster
Member Since: Posts: Comments:
Check out the radar from the islands there is clearly a circulationLink visible
Member Since: Posts: Comments:
Quoting MississippiWx:
This just gets worse every day:



Of course! The water temperaures climatically begin to cool in about a month or so! And since the SSTs are so darn warm, in october or November, the SSTs may be where normal is considered for August-September!
Member Since: Posts: Comments:
Navy says Colin is a TS so i think when next rec flight goes out the will find that the COC is closed. Plus it looks quite impressive on the sat.
Member Since: Posts: Comments:
doom i say where all doom
Member Since: Posts: Comments:
1042. will45
Quoting MahFL:
Colin is a fish storm......
fish dont live on land in Bermuda
Member Since: Posts: Comments:
Quoting MississippiWx:
This just gets worse every day:




yup with that heat wave going on back there
Member Since: Posts: Comments:
1040. xcool
MississippiWx 9 / we doom
Member Since: Posts: Comments:
Quoting Snowlover123:


18Z GFS shows a 1009 mb low near Africa, and is the disturbance we are currently monitoring at the moment, and shows ex-Colin re-develop, and is currently heading NW, along the edge of the Bermuda High.
Actually has the African wave as a TD there. Notice the closed isobar along with the wind barbs indicating a closed low. It also has ex-Colin as tropical storm Colin.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Drakoen:
It would be difficult for me to believe there is not a closed circulation now associated with Colin based on these surface observations:



Not to mention the impressive convective feedback from this storm! -80 Degrees C! Wow!
Member Since: Posts: Comments:
This just gets worse every day:

Member Since: Posts: Comments:
Quoting HurricaneSwirl:


There is a new center under the giant ball of new convection.


Also according to the last ATCF fix the center is around 19.4N and 61.2W.. looks good to me.
Member Since: Posts: Comments:
1034. MahFL
Colin is a fish storm......
Member Since: Posts: Comments:
Quoting Snowlover123:


Could you provide a source for that?



not sure i can
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Link

This shows the low level circ center at around 19.7 N 65 W, hundreds of miles southwest of the main convection. Is there another circ center under the convection? Can't say, but if it's not obvious, it can't be strong.

If the convection to the NE takes over and becomes a storm, I think the trough will carry it out.

If the naked swirl NE of Puerto Rico can get some convection, could be a threat. But that naked swirl has a long, long, long way to go.


The center you are seeing is the old center, which it has shed. Look at the vorticity maps and see that there is a center under the ball of convection, which has most likely made its way down to the surface.
Member Since: Posts: Comments:
1031. Drakoen
It would be difficult for me to believe there is not a closed circulation now associated with Colin based on these surface observations:

Member Since: Posts: Comments:
Quoting Tazmanian:



be come the map may say 10 too 20kt but if you look at the IR it could be more like 5 too 10kt


Could you provide a source for that?
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Link

This shows the low level circ center at around 19.7 N 65 W, hundreds of miles southwest of the main convection. Is there another circ center under the convection? Can't say, but if it's not obvious, it can't be strong.

If the convection to the NE takes over and becomes a storm, I think the trough will carry it out.

If the naked swirl NE of Puerto Rico can get some convection, could be a threat. But that naked swirl has a long, long, long way to go.


There is a new center under the giant ball of new convection.
Member Since: Posts: Comments:
1028. xcool
mommy wow Colin
Member Since: Posts: Comments:


18Z GFS @ 36 hours shows a 1009 mb low near Africa, and is the disturbance we are currently monitoring at the moment, and shows ex-Colin re-develop, and is currently heading NW, along the edge of the Bermuda High.
Member Since: Posts: Comments:
I noticed yesterday and again today that the TUTT feature between Bermuda & PR seems to be lifting out to the North. Less wind shear means Colin is in less unfavorable conditions.

If TUTT moves out does that mean it will stay further North for the remaining Hurricane Season? This would leave the door open for a Frances type storm.
Member Since: Posts: Comments:
Quoting extreme236:


Well it is important to keep in mind organization matters also when it comes to classifying systems. A closed circulation with a T1.0 system would mean nothing. At least were looking at T1.5 and 2.0 now.
Agreed.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1022. 7544
looks like a stall coming up soon imo its hardly moving now just spining and gaining more and more conv,

strom w ?
Member Since: Posts: Comments:
Quoting Snowlover123:


Why do you think it is off?



be come the map may say 10 too 20kt but if you look at the IR it could be more like 5 too 10kt
Member Since: Posts: Comments:
GFS 18z 24 hours - Has ex-Colin with a closed isobar. Also notice that the wave near 30W develops an area of low pressure.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting xcool:
SeniorPoppy Pull-Ups lol


LOL...yea
Member Since: Posts: Comments:
1018. will45
Quoting extreme236:


Well it is important to keep in mind organization matters also when it comes to classifying systems. A closed circulation with a T1.0 system would mean nothing. At least were looking at T1.5 and 2.0 now.


and consistance for a time
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Whatever the case, it's too disorganized to be a TS before 5 am.


All it needs is a closed LLC...Thats it.
Member Since: Posts: Comments:
1014. xcool
SeniorPoppy Pull-Ups lol
Member Since: Posts: Comments:
Quoting Tazmanian:




and that shear map could be a little off


Why do you think it is off?
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
More like T2.0. At least this time they don't have to base the advisory off of the satellite estimate but rather what Recon finds.


Well it is important to keep in mind organization matters also when it comes to classifying systems. A closed circulation with a T1.0 system would mean nothing. At least were looking at T1.5 and 2.0 now.
Member Since: Posts: Comments:

Viewing: 1062 - 1012

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 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Scattered Clouds
73 °F
Scattered Clouds