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

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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

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2512. aquak9
Quoting MahFL:
So when will the big one hit FL again ? I thought the pattern favoured FL this year ?


sigh...no one can answer that.
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Morning TU all. Here in Puerto Rico EX-Collin left us suffocating in the heat. Southerly winds not good at all here.
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Quoting tkeith:
I see you're comin to the Big Easy this weekend. Local mets say it's gonna cool down all the way to the "mid 90's" :)


Will Have to remember to bring my Jacket!!
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2509. tkeith
Quoting traumaboyy:


Yes sir, about 15 miles north of Blountstown
My buddy is 25 years old, you may know him.
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2508. aquak9
G'morning Seenya Cheef.

Except for the heat and lack of rain (my area), I think we're enjoying the tropics so far.

I know, that'll change...
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Quoting tkeith:
Is that on the same side of the river as Blountstown?


Yes sir, about 15 miles north of Blountstown
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2506. tkeith
I see you're comin to the Big Easy this weekend. Local mets say it's gonna cool down all the way to the "mid 90's" :)
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2505. MahFL
So when will the big one hit FL again ? I thought the pattern favoured FL this year ?
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2504. tkeith
Quoting traumaboyy:
Is Gran

Is Grand Ridge Close enough?
Is that on the same side of the river as Blountstown?
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Is Gran
Quoting tkeith:
Trauma are you near Blountstown? A guy that works for me is from there.


Is Grand Ridge Close enough?
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2502. IKE
108 hr. 6Z GFS forecast....Colin is completely history by then. Looks like 93L may come from the blob in the eastern ATL, but it looks like a fish system....

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2501. tkeith
Trauma are you near Blountstown? A guy that works for me is from there.
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2499. tkeith
mornin Storm.
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Quoting StormW:
Thanks Korie and Trauma.

Thanks again Trauma for all of your help!


My honor Chief!
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Yes, tkeith. Virginia Beach - about 5 mile ese of the Norfolk airport
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Going to be hot & humid here today - and a good chance of boomers late this afternoon.
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2495. tkeith
CW you in Virginia?
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2493. tkeith
they were moving NE to SW. "backdoor storms"
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Morning again -. Aqua, Ike, tkeith, et al.
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2491. IKE
Good morning cyberspace. Precip was all around me yesterday. None fell at my location.
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2490. aquak9
g'morning ike and tkeith. Send some rumblin rain this'away.
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2489. tkeith
mornin Ike and Aqua et.al.

Had some nice thunderstorms come through last night about 10:00pm.
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2488. IKE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
549 AM AST THU AUG 5 2010

.SYNOPSIS...THE REMNANTS OF TROPICAL STORM COLIN LOCATED WELL NORTHEAST
OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS EARLY THIS
MORNING...WILL CONTINUE MOVING NORTHWEST AND AWAY FROM THE LOCAL
AREA TODAY. A MODERATE TRADE WIND FLOW WILL THEN PREVAIL ACROSS
MOST OF THE REGIONAL WATERS FRIDAY THROUGH SATURDAY. UPPER LOW
WILL CONTINUE TO OUR NORTHWEST AT LEAST THROUGH FRIDAY.

&&

.DISCUSSION...ONLY LIGHT PASSING SHOWERS WERE NOTED ACROSS THE
LOCAL AREA OVERNIGHT. SCATTERED SHOWERS WERE NOTED ACROSS THE
CARIBBEAN AND ATLANTIC WATERS. REMNANT OF TROPICAL STORM COLIN
LOCATED NEAR 300 MILES NORTHEAST OF THE LOCAL AREA...WILL CONTINUE
TO MOVES AWAY FROM THE LOCAL REGION. WINDS WILL CONTINUE MAINLY
FROM THE SOUTH...WHICH WILL INDUCE HIGHER THAN NORMAL TEMPERATURES
MAINLY ACROSS THE NORTHERN HALF OF PUERTO RICO. THIS WEATHER
PATTERN IS EXPECTED TO PREVAIL AT LEAST THROUGH SATURDAY.
HOWEVER...WEATHER CONDITIONS WILL RETURN TO NORMAL FOR THIS
MONTH...WHEN A HIGH PRESSURE SYSTEM ACROSS THE CENTRAL ATLANTIC
IS EXPECTED TO BUILD ACROSS THE NORTHEAST CARIBBEAN BY SUNDAY. BY
THEN...ONLY AFTERNOON SHOWERS ARE EXPECTED ACROSS THE CORDILLERA
CENTRAL...OVER THE INTERIOR SECTION OF PUERTO RICO. IN THE LONG
TERM...NO SIGNIFICANT WEATHER EVENTS ARE FORECAST TO AFFECT THE
LOCAL AREA AT THIS TIME.


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2487. aquak9
g'morning WU-bloggers worldwide, good evening Aussie if you're here.

Pottery- if you're here- I went outside in the dark to feed m'cat, looked up at the stars. They were smiling, shining so bright, I thought of Ebony, I think she's a very happy pup once again. ♥
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2486. HadesGodWyvern (Mod)
Philippines Atmospheric Geophysical Astronomical Services and Administration
Tropical Cyclone Bulletin #8
TROPICAL DEPRESSION DOMENG
5:00 PM PhST August 5 2010
=============================================

Tropical Depression "Domeng" has maintained its strength as it traverses the Balintang Channel on its way out to the South China Sea.

At 4:00 PM PhST, Tropical Depression Domeng located at 19.5°N 119.6°E or 140 kms northwest of Laoag City has 10 minute sustained winds of 25 knots. The depression is reported as moving west at 9 knots.

Additional Information
========================
Public Storm Warning signal elsewhere is now lowered.

Meanwhile, the Low Pressure Area was estimated based on satellite and surface data at 930 kms East of Northern Luzon near 18.2°N, 132.0°E.

The combined effect of Tropical Depression "Domeng" and the Low Pressure Area East of Northern Luzon will enhance the Southwest Monsoon and bring rains over the country particularly the western section.

The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 11 PM today.
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I am in NW florida...headed to NOLA next week for some fun....looks like it will be mostly pool time
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I love StormW so much I drove to Tampa to help him move for free....that dude rocks!
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Morning, all. Heat and humidity have returned to Hampton Roads - heat warnings are up. Going to skim back through the last couple of pages to catch up now that I've had my coffee..

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Quoting traumaboyy:
Kori Looks like I picked a bad time to come to New Orleans if it is that hot out there!


Oh, you're in NOLA? Are you a Louisiana resident, or are you here on vacation, business, etc.?
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Quoting pottery:

I guess 'not busy' is good, in Trauma.
I get educated here as well.
Have learned plenty from these guys like Kori and others.


Thanks for praising me. I've in turn learned from people wiser than me, like StormW.
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Quoting pottery:

I was seeing that.......
That kind of heat would be too much for me.
Seems that there is no middle ground these days.
Too hot. Too cold. Too wet. Too dry......


It does seem that way. Though at least we've been getting some luck with regards to hurricane season and the oil spill. Bonnie was a no go, and so far nothing else has greatly hampered the cleanup efforts.

Here's to hoping it stays that way.
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Kori Looks like I picked a bad time to come to New Orleans if it is that hot out there!
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2478. pottery
Going to brew some coffee......
BBL
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2477. pottery
Quoting traumaboyy:
I am at work, get paid to be entertained by you guys....when I am not buzy!

I guess 'not busy' is good, in Trauma.
I get educated here as well.
Have learned plenty from these guys like Kori and others.
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2476. pottery
Quoting KoritheMan:


I'll trade you my sunshine for your deluges. It's been oppressively hot here, with heat indexes in excess of 115 to 120F for the last four or five days. No relief in sight today, either.

I was seeing that.......
That kind of heat would be too much for me.
Seems that there is no middle ground these days.
Too hot. Too cold. Too wet. Too dry......
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correction....entertained and EDUCATED!
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I am at work, get paid to be entertained by you guys....when I am not buzy!
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Quoting pottery:

Yeah! Doing Good, thanks.
Looking forward to a little sunshine today before the next deluge!!


I'll trade you my sunshine for your deluges. It's been oppressively hot here, with heat indexes in excess of 115 to 120F for the last four or five days. No relief in sight today, either.
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2472. pottery
Quoting traumaboyy:
Morning guys!

Hi!
Dont you ever sleep LOL?
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Morning guys!
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2470. pottery
Quoting KoritheMan:


Good morning. Hope you're doing well.



I've been thinking that since yesterday. Its dropping from the NHC surface map at 0000 UTC had nothing to do with that.

Yeah! Doing Good, thanks.
Looking forward to a little sunshine today before the next deluge!!
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Quoting pottery:

Morning, Kori.
I agree with you. I kind of hope it does develop a little, and that will tend to swing it north away from the Islands.
We have had too much rain already, and that area looks dread for the Islands if it keeps coming this way........


Good morning. Hope you're doing well.

Quoting ellesukwthrfanatic:


Do you think the Carribean invest will come to nothing now?


I've been thinking that since yesterday. Its dropping from the NHC surface map at 0000 UTC had nothing to do with that.
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Quoting KoritheMan:
Pre-Danielle looking good:



Do you think the Carribean invest will come to nothing now?
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2467. pottery
Quoting KoritheMan:


Well, right now the models are flipflopping with regards to its intensity, with most of them having backed off significantly on the expected intensity of the system at 0z. The reason for this is quite unclear, since the upper wind environment greatly favors additional development over the next several days.

The weaker it goes, the more equatorial (west) it will move, owing to the uniform low-level easterly flow common of the tropics.

Conversely, a stronger system, as the models were predicting at 18z (and what the GFS still predicts), would tend to follow a path out to sea like Colin.

The forecast is uncertain, but given current organizational trends, and the forecast upper wind environment, I tend to favor the recurvature scenario.

Morning, Kori.
I agree with you. I kind of hope it does develop a little, and that will tend to swing it north away from the Islands.
We have had too much rain already, and that area looks dread for the Islands if it keeps coming this way........
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Quoting ackee:
Any chance it will not be a fish storms


Well, right now the models are flipflopping with regards to its intensity, with most of them having backed off significantly on the expected intensity of the system at 0z. The reason for this is quite unclear, since the upper wind environment greatly favors additional development over the next several days.

The weaker it goes, the more equatorial (west) it will move, owing to the uniform low-level easterly flow common of the tropics.

Conversely, a stronger system, as the models were predicting at 18z (and what the GFS still predicts), would tend to follow a path out to sea like Colin.

The forecast is uncertain, but given current organizational trends, and the forecast upper wind environment, I tend to favor the recurvature scenario.
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2465. ackee
Quoting KoritheMan:
Pre-Danielle looking good:

Any chance it will not be a fish storms
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.
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Pre-Danielle looking good:

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

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