2009 Atlantic Hurricane Season

[summer blizzard]

With all the forecasts from various agences being released, i thought it would be better for any new dicussion points to take place in one thread..

In regards to the forecast for the 2009 hurricane season, i've taken a look at the data and taken some cliff notes...

- Strengthening weak LaNina since November

- Strengthening strong negative PDO since December

- Weak polar vortex

- Weakening westerly QBO after secondary peak

- MEI summer

- PDO summer

- AO summer

With this in mind i would say that the prospects for this season are good, with a La Nina in place we should see faviourable Atlantic conditions, with low angular momentum meaning a stable pattern, however the fly in the oitment is the indication for a lot of high lattitude blocking which could force a more southerly tracking Jet Stream leading to increased shear and a weakend ITCZ.

Because of this, i would say that this will not be a Cape Verde season and the main bulk of activity will occur in or around the Carribean with an above average number of named storms and Huuricanes, along the lines of 15/8/4 when major hurricanes are taken into account.

Note: This is not my offical forecast which will be released in May.

[Iceberg]

I am rather in the mind that Shear will be extremely weak(close to record breaking weak) until the end of Aug. Then it will pump up markedly as Kold and the other forecasters say.

A last minute decision in May though will be required for this. But my prediction will probably be a record 4 week period from mid July to Mid August, which might contain 50% of the entire seasons storms.

6 weeks or so and counting though.

[kold weather]

Very interesting SB, I think El Nino will probably be a big factor towards the second half of Autumn and you really only need to get towards +0.8C for it to shut a hurricane season down early, as we saw with 2004 and 2006. Of course with 2004 we had a very active phase helped by some very warm waters.

For now the waters are if anything slightly below average overall in the mean development region which would be suggestive of average-below normal activity IF the El Nino does come along. However I think its a little too early to call the El Nino type event plus I think the waters will warm up back towards slightly above average and thus I think from July-September we will probably have an above average phase but it could be quickly flattened by an increase in shear as El Nino develops.

I've said this a few times but for now my numbers would be 12/6/3, rather close to various forecasting agencies, and for the bulk of that to occur in a 2 month period between mid July and Mid September.

[Cookie]

nice to see the experts view. thanks guys :unsure:

[Tn9]

Sea Surface Temperatures (SSTs) and deep water temperatures have warmed significantly in the equatorial Eastern Pacific over the first two weeks of April, and La Niña conditions are no longer present. While NOAA's Climate Prediction Center has not yet declared an end to this La Niña episode and dropped their La Niña advisory, it is very likely that the La Niña event that began in December 2008 is now over. The big question is whether an El Niño event will rapidly form in its place, in time for hurricane season. This did happen after the 1976 La Niña, which ended in April, with a weak El Niño beginning in September. However, it can take a few months for the atmosphere to adjust to the formation of a new El Niño, and there is no guarantee that a weak El Niño for the coming hurricane season would act to dramatically reduce Atlantic hurricane activity.The number of Atlantic hurricanes is typically reduced in an El Niño year, due to increased wind shear from strong high-level winds. Nearly all the model forecasts for the Niño 3.4 region predict neutral conditions for the August - October peak of hurricane season. Four out of 21 El Niño models are predicting an El Niño event for hurricane season; three are predicting a La Niña, and fourteen are predicting neutral conditions.

Figure 1. The difference of Sea Surface Temperature (SST) from average for the Niña 3.4 region of the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W). La Niña conditions are defined as occurring when the 1-month mean temperature anomaly in the Niña 3.4 region cools below -0.5°C. La Niña conditions began in December 2008 and ended in late March 2009. Image credit: NOAA Climate Prediction Center.

Tenth warmest March on record for the globe

Global temperatures remained about where they've been the past two years, with the planet recording its 10th warmest March on record, according to statistics released by the National Climatic Data Center. The period January - March was the eighth warmest such period on record.

An average March for the U.S.

For the contiguous U.S., March temperatures were the 51st warmest in the 115-year record, according to the National Climatic Data Center. The month had near-average precipitation, ranking as the 42nd wettest March. Three states (Delaware, Maryland, and New Jersey) experienced their driest year-to-date period ever. In neighboring states, Pennsylvania recorded its second driest year-to-date period and Massachusetts and West Virgnia experienced their fourth and fifth driest, respectively. The below-normal precipitation averages led to the driest ever start to the year for the Northeast region. Record amounts of snow fell in North Dakota during March. Fargo received 28.1 inches, which was nearly 2 more inches than the previous March record set in 1997. Fargo also recorded 4.62 inches of precipitation which set a new monthly record. Runoff from the record precipitation led to the highest flood levels ever observed on the Red River in North Dakota. The river crested in Fargo at a record level of 12.4 m (40.8 feet), shattering the previous record of 12.2 m (40.1 feet) set in 1897.

Through March, the U.S. has only seen about 50% of normal tornado activity for the year, according to NOAA's Storm Prediction Center. There were just 9 tornado deaths through March, compared to 70 deaths through March of 2008, and the 3-year average of 44 deaths.

On April 14, 2009, 17% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 21% figure observed January through March.

Bahamas 2009 Weather Conference

This week, many of the world's hurricane experts are gathered at the Bahamas Hurricane Conference. Check out their web site for short videos by some of the presenters. The 3-minute talk by NHC Director Bill Read and former NHC Director Max Mayfield on the inadequacy of our familiar Category 1-2-3-4-5 Saffir-Simpson scale is interesting. They make the point that no one scale will ever be able to capture the threats a hurricane poses, since these depend greatly on exactly what track the storm takes, and our forecasts will never be able to precisely pinpoint the track. Thus, introducing a new scale to quantify storm surge risk is not a complete solution to the inadequacies of the Saffir-Simpson scale. Coastal residents need to heed the detailed wind and storm surge forecasts for their area, regardless of what Category storm is approaching.

Jeff Masters