The climate researchers at Colorado State University have released their spring forecast for the 2009 Atlantic hurricane season, and it’s calling for a relatively normal number of storms compared to average. The outlook is for 12 named storms, six hurricanes and two intense (category 3 or greater) hurricanes. The average from 1950-2000 is 9.6 named storms, 509 hurricanes and 2.3 intense hurricanes per year. There is a 54% chance of a major hurricane striking the US coast this year.

To develop their April forecast, the CSU researchers use a combination of observed sea surface temperatures in the Atlantic and sea level pressure off the African coastline in early spring. The observed values tend predict how much wind shear there will be from August through October, the heart of the hurricane season. The forecasters also look at analog years, where weather conditions are similar to this year. The number and intensity of storms in those years should be similar to what we get this year. Analog years for this season are 1951, 1968, 1976, 1985 and 2001.

The researchers also look at the chances of there being an El Nino or La Nina during the late summer. In El Nino years, the amount of tropical activity tends to diminish. Right now, we are in a weakening La Nina (cold sea surface temperatures in the central Pacific). There is a 50% possibility that La Nina conditions will develop by summer, and this caused the team to moderate its December forecast, which had called for 14 storms and seven hurricanes.

You can read the full forecast (PDF) here.

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Earlier this week, the Dr. Gray and his team at Colorado State University issued their initial outlook for the 2009 hurricane season. The early outlook predicts a continuation of the above-normal tropical activity we’ve seen over the past few years. The outlook is for 14 storms, compared to over nine in a normal year, and seven hurricanes, compared to six in a normal year. There should be three major hurricanes, and there’s a 63% chance of a major hurricane making landfall somewhere in the United States–about 20% greater than in a normal year.

Last year at this time, CSU predicted there would be 13 named storms, seven hurricanes and three major hurricanes. The result ended up being 16 storms, eight hurricanes and five major hurricanes, so they underestimated. However, their new model for predicting hurricanes from this far out is apparently more accurate than the model they used previously.

A few other weather tidbits:

if tonight’s full moon seems brighter than usual, it’s because the moon is closer to the earth than it’s been for the past few years, and the first time in 15 years that the close approach, caused by the Moon’s elliptical orbit, has occurred during a full moon. Coincidentally, the moon is riding higher in the sky than any other full moon this year. The sun and moon follow opposite visual paths–when the sun is low close to the winter solstice, the moon is high in the sky, while in the summer, when the sun is overhead, the moon is low in the sky.

Another astronomical factoid — today is the first day that the sun begins to set later in the evening than it has since back on July 5th. Day will continue to shorten for another ten days, due to the sun rising later. We won’t get an earlier sunrise until January 13th.

The storm that brought welcome rain to much of the southeast is now history, having moved up the east coast and causing major power outages in the northeast. Much of Massachusetts was caught in an ice storm, with considerable damage. Albany, New York had .6 inches of ice, while Schenectady reported .88 inches of accumulated ice.

We are about to see a big pattern change in the weather across the United States. The past month or so has been dominated by an upper level trough in the east and a ridge in the west. This pattern brought warmer than normal conditions to the west, and colder than normal weather to the east, as the jet stream dived south, following the path of the trough.

Now, a trough is developing in the west, which will bring colder than normal weather there, but more seasonable, if not warmer than normal weather to the Southeast. There’s a better than normal chance of above normal temperatures for most of the south through Christmas, and it looks like we’ll get some additional rainfall, too. Lake Lanier’s current level is 1051.88 feet–more than ten inches above where it was on Wednesday before it started to rain. The AJC reports that yesterday was the first day since the record low level last December that the lake level in 2008 was higher than it was on the same day in 2007.

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The August heat wave looks like it will go on through Thursday, but at least here at my house, today was the warmest day so far in 2008. It got up to 99 degrees (well, 98.7) at 2:10 PM, topping the 97.1 reached on both June 8 and July 10. It could have been worse though: with the dew point in the low 60s, the heat index was only 102 degrees.

Temperatures reached the century mark today in Augusta, Milledgeville, Savannah, Athens and Vidalia. For whatever reason, it stayed a bit cooler in Atlanta today, with highs only in the low 90s. Tomorrow, the humidity goes back up, and by tomorrow afternoon, the approaching front will bring a chance of rainfall, and at least a temporary end to the excessive heat we’ve been seeing recently.

Hurricane Forecast Update

We’re about ready to get into the strongest part of the hurricane season, from mid-August through the end of October.  The folks at Colorado State University have updated their tropical forecast and are now calling for more storms than they predicted back in April and repeated in June.

Instead of 15 named storms, the predicted total has been upped to 17, with nine hurricanes, instead of eight. Five of those should be intense, compared to four predicted previously.  Part of the reason for upping the predictions is the number of storms we’ve seen through July, with four named storms, two hurricanes and one intense hurricane. That doesn’t count Edouard, which was the first storm in August.  According to the forecast, only 2005 (the year of Katrina) and 1916 have had more active pre-August tropical activity.

There’s a 2/3 chance of a major hurricane making landfall somewhere in the US during the rest of the season, with a better than 40% chance of a storm striking either the east coast or the gulf coast.  Overall, the forecasters are predicting a tropical season that is 190% as active than the average season from 1950-2000.

In addition to providing forecasts for the rest of the season, the Dr. Gray and his team are providing a forecast for August tropical activity. If they are right, we will have four storms, three of which will become hurricanes, and one intense hurricane this month. With Edouard already occuring, that’s the non-hurricane storm, if their forecast is correct. They will also issue forecasts for September and October at the beginning of those months.

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The temperature here in Lawrenceville topped 90 degrees for the first time in 2008 today, with a maximum of 91.4 degrees at 2PM.  In Atlanta, today’s high was only 89.  But in any case, they’ll have another chance tomorrow and indeed for the next week or so, as we are under the influence of an upper level high pressure system that will keep the warmer than normal temperatures around, and probably keep the rain away as well.

All in all, temperatures are running about 6 degrees above normal for early June.  And, this is about the usual time we see 90 degrees — last year we topped 90 on June 6th, in 2006 on May 24th, and in 2005 on June 14th.

Longtime blog reader Morgan Kemp reminds us of the ongoing drought by posting some comments by Georgia climatologist David Stooksbury made at this time last year, when the drought’s effects were really setting in. Actually, we’re doing a bit better this year through May.  While most of Georgia had less than normal rainfall for the month, Atlanta is only 4 inches short of normal for the year, and Athens has had 6.4 inches less than what would be expected.  Through the end of May, Atlanta recorded 18.65 inches of precipitation for 2008, compared to 11.73 inches for the same period in 2007.

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With less than two months until the start of the Atlantic tropical season on June 1, the forecasting team at Colorado State University has updated its forecast, and is now calling for a more active season than originally predicted last December.

Drs. Klotzbach and Gray are estimating that there will be 15 named storms and eight hurricanes in 2008, with four of those being intense hurricanes.  This compares to the December forecast of 13 named storms, seven hurricanes, and three intense hurricanes. Between 1950 and 2000, there were, on average, 9.6 named storms, 5.9 hurricanes, and 2.3 intense hurricanes each year.  Overall tropical activity is predicted to be 160% of normal.

There is a 99% chance that some sort of tropical activity will cross the US coastline this year, with a 69% chance of a major hurricane making landfall.  There is a 44% chance that a major hurricane will strike the Gulf Coast, and a 45% chance that a major hurricane will strike the East coast or the Florida peninsula.

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