Cool conclusion to September now to be followed by Indian Summer episodes for Central and Eastern States.

Northeast:

As we advised last week, a transition to a positive NAO phase is helping to break-up the very cool September pattern.  This will be manifesting itself in the form of periodic Indian Summer episodes during the month of October (quantified in our last ENSO Report).  Pleasantly warm October temperatures for Northern States should not be viewed as Summer-like, in much the same manner as October cool snaps should not be viewed as Winter-like quite yet.

Southeast:

The NAO-induced Trough is finally lifting which will allow much warmer weather to return to this region as the week progresses. Lingering Summer drought inland from the Atlantic Ocean will help boost some late-Summer days well into the 80's, topping off what has been a blistering Summer for many Gulf Coast States.

North-Central:

It was and is important to view the cool weather in September as a crisp conclusion to the Summer Season, and not the "onset of Winter".  This point was further illustrated with temperatures recently surging back into the 80's as far North as the Dakotas and Minnesota, kicking off October 2006 on an anomalously warm note.  This will reinforce the very warm Great Lakes water temperatures (above 60°F for all except Superior), which sets the stage for Lake-Effect clouds, rain showers and eventually snow.

South-Central:

Lingering drought (away from the Gulf) have been helping to yield some late-Summer hot days (Dallas has his at least 94°F the past 3 days), topping off what has been a record-setting Summer for many South-Central locales.  These regions become much more vulnerable to cold frontal passages as we approach and go through October, but afternoon readings nearing 90°F remain possible for weeks to come.

Northwest:

Temperatures have already rebounded to more Seasonable levels over the past week as the trough weakened and slid eastward. Surface conditions have dramatically dried out from the Northern Rockies to the Pacific shoreline over the past 2 months, so with ridging shifting West at times, the potential for more anomalous warm periods remains probable for the next few weeks (as does corresponding wildfire threats).  An abatement or reversal of the recently positive PNA will quickly cool off the Northwest in October however, and could give some locations their first freeze events of the Season.

Southwest:

Phase fluctuations of the PNA teleconnection will continue to increase intra-month and intra-week variability. Some of the wildest temperature swings will be featured across the Rockies, where Denver dropped into the 30's in mid-September and now has already strung together 5 consecutive days over 80°F.  Unfortunately wildfire risk remains critical across most of Nevada and California, where windy weather from patterns shifts only add insult to injury.

Tropics Status:

Eastern Atlantic Tropical Wave: In the short term, upper level wind shear is too strong for this to develop further; however, if it can hold together past 72 hours or so, it may run into more favorable conditions farther to the West as it approaches the Leeward Islands.

Other areas of interest: There is a non-tropical low pressure system between the Cape Verde Islands and the Azores that needs to be watched for Sub-tropical development. This would only be a tally in the named storms category as it is much closer to Europe than North America. We will be closely monitoring tropospheric impulses that are meandering their way across the Pacific towards the Atlantic basin over the next week or so. Look for shower and thunderstorm activity to wake up from its current lull soon after the Columbus Day Holiday, and these low pressure areas should spark a similar flurry of activity that we advised back before the first two weeks of September.

{FYI: During the 2004 and 2005 Seasons, NHC declared the first classification of a tropical system in either their 5 PM or 11 PM advisory periods an imbalanced 65% of the time, and outside of the work day (i.e. post-4 PM and Weekends) an imbalanced 80% of the time.  So far in 2006, TD # 1 (later ALBERTO) , TD #6 (later FLORENCE), and TD #7 (later GORDON) were initially classified over a weekend, and TD # 3 (later CHRIS) ,TD # 4 (later DEBBY)  and TD # 5 (later ERNESTO)  and were all initially classified during the weekday evening hours.}

Related link of interest (Historical Hurricanes Impacting New York): 

http://www.weather2000.com/NY_Hurricanes.html