Desert Southwest Heating Up

[azskyman]

Beware the Ides of March!

We worked our way up to 89 today, and this week looks like a string of days with temps around 90. Morning lows in central Phoenix will cling to near 60...in my area about 52-55.

Not unusual to have warm to hot days in March, but stringing them out like this is somewhat uncharacteristic of recent years.

Don't quite see our first 100+ on the horizon yet, but this reminds us of hot days ahead.

[therock1811]

That's hot for March anywhere...

[cycloneye]

Ummm imagine when the summer months come Steve those high temps will be at the century mark every day.

[Guest]

what happens when we get the next longwave as the south from the Southwest to the Southeast warms up!
It will be a nasty system from what I see in the GFS, but I'm not hanging on it yet!

[azskyman]

Hi Bob...impressed by your home page for weatherwatchers. I'll bet we know some of the same weather enthusiasts in FL. What city are you located?

Yes, early heat down south can truly be a forerunner of fiesty weather as spring gets cranked up. We'll all be watching to see what it means in the days and weeks ahead.

Keep up the good work, sir!

[Aslkahuna]

of my March temperature data going back to 1988, I noted that since 1996 March had tended to be cooler than the running mean with shorter duration warm spells and greater tendency towards freezes here. This trend seems to be reversing a bit as the last two Marches have been warmer. We could be entering a new cycle of warm Springs or this could just be a blip-hard to tell at this point in time. One thing is clear, the rainfall patterns are undergoing a change from dry statewide to one where certain areas are getting good rains as witnessed by the fact that we here are running well ahead of normal for YTD rainfall. Whether this is a precursor to the end to our drought remains to be seen. We are now in the 8th year of the current drought and the average duration of these every 20 year droughts in the West is about 10 years though they have lasted longer (up to 40 years in one instance).

Steve

[Guest]

is Northeast Florida. About 30 miles from Jacksonville.
Now you mention the timing of the droughts. have you been able to coicide it with a possible upswing in the PDO(Pacific decadel Oscilation).
It could very well be a indicator, and with much research still being done, maybe someone would be interested in your findings. Just an idea.

[Aslkahuna]

of the PDO is a player in the Drought Cycle but is not the underlying cause. The 20 year cycle operates regardless of the phase of the PDO though during positve phase years the drought might be less intense than during negative phase years. We had a Drought in the 1970's which occurred during a positive phase of the PDO. The 20 year Drought cycle has been operative as far back as we have been able to determine from dendrochronology studies so we have to look elsewhere than the PDO for the main signal that triggers the Droughts in the West and Southwest. OTOH a prolonged PDO negative phase can prolong a Drought.

Steve

[Guest]

In a positive PDO? I haven't had much time lately to check into it. But overall, it would explain a lot of things, especially the El Ninio type patterns we have seen with some periods of the past Winter Season. Even though we are in a neutral ENSO.

[Stormless2003]

Are there any connections between the PDO and the frequency of severe weather events in the central US? The last several years have featured well below normal storm activity during the late winter/early spring. In 2001 the US only had 68 tornadoes from January through the end of March. In 2002 the US only had 52 tornadoes during this 3-month period, and 61 in 2003. So far, the 2004 season is running even further behind yet, with only 32 tornadoes as of today. The 13-year average for Jan-March is about 140. Could this be a sign of a long term shift towards less stormy late winter/early spring seasons, and if so, what caused it?

[Guest]

The first question we would have to ask ourselves. What weather phenomenom, such as ENSO, NAO, PDO, ect would play a part in this?
By just knowing off the top of my head, we have been in a near neutral ENSO for about 18 months, and before that a weak La Nina, and before that a weak El Nino. In the 1990's we had strong El Nino's, so could this have been a factor on the 13 year average?
Looking further, will a Neutral ENSO create less periods of stormy patterns, but each individual storm session would be more intense? During an El Nino, we would expect a spring storm about every 3-4 days. Now, we're experiencing them about every 4-6 days. Would this be because of the lack of El Nion/La Nina influence on weather patterns across the Conus?
These all play a part, including the NAO, and even the longer term PDO, let alone other weather phenomenom around the globe.
It will take researchers decades to piece it all together, but they have been making leeps and bounds the past 10 years!!

[Aslkahuna]

was in a positive (warm) phase until about 1996 when it began to shift into a negative (cold) phase. However, there is strong intra-phase variablility in the PDO and it has been trending a bit warmer as of late though it seems to be going back cold. There was a peak of the negative phase in 2000 which coincided with a strong La Niña resulting in a storng monsoon here. Niño's tend to give us wet Winters/Springs and late starting and more violent and erratic monsoons (last Summer being a perfect example of a Post-Niño monsoon). However, a negative phase of the PDO will blunt the Winter effects of a Niño while having little effect upon the Summer. This is because a major source of the monsoon activity comes from disturbances originating in the GOM with dual moisture sources. During the early to mid 90's when the PDO was positive, we had great Winter rains due to frequent and prolonged Niños which were enhanced by the PDO. But since, even the very strong Niño of 1997-98 was reduced in effectiveness by the negative PDO and quickly transtioned into a strong Niña which is not good for Winter rains here. The last Niño (2002-03) was not at all effective here in the Winter and the drought feedback (which is becoming increasingly important) is resulting in precipitation ineffective monsoons despite the fact that they have been active. During a neutral ENSO, the MJO becomes a major player in the periodicity of weather occurrences in the West-especially from Central CA northward where it plays an important role in the Pineapple Express events. The difficulty in sorting all of this out, of course, is that all of these oscillations are interrelated to each other and to the state of the underlying surface and, there are probably Southern Hemisphere oscillations that can affect what we see. Important to note-the monsoon regions of the World have one characteristic that's very important. It is there that we see cross equatorial exchanges of arimasses between hemispheres and, of course, are the most likely areas where cross relationships in the atmosphere between them are likely to originate. Add to this the uncertainty as to the actual magnitude of energy change taking place in the atmosphere due to outside influences but anthropogenci and natural (otherwise known as Global Warming) and it's potential influences upon both the atmospheric and oceanic circulations and the potential feedback from the latter and we end up with a bucket rather than a can of worms.

Steve

[azskyman]

96 today...the first FULL day of spring. Knew it was going to heat up plenty when it was 77 degrees at 0500!

Windy today too.

[Aslkahuna]

was the first Full Day of Spring in AZ since the Equinox occurred at 11:49pm on the night of the 19th. We hit 84F Saturday, but only hit 76F yesterday with easterly winds from a backdoor front. Today is also in the 70's.

Steve

[Guest]

what are they saying out there aboutthe low pressure over the weekend?
The models bring that large low pressure into Califinia and across the southwest.

[Aslkahuna]

the forecasts are calling for unsettled breezy and cooler with mountain showers but nothing down here. As we get further into Spring, the systems tend to become blowhards and little else since the dynamics needed to deepen the Marine Layer enough off of SoCA and Baja to get moisture over the mountains there are no longer present-unless we either get an unseasonably intense system or a subtropical one neither of which the incoming one is expected to be.

Steve

[azskyman]

Sunday was the hottest here, and today with drier air and full sunshine we topped 90 again but will drop back further tonight than the last two.

I can't recall spring actually arriving on the 19th over the years, Steve, so I appreciate knowing that it can, and does. Made a lot of calendars wrong for those of us here in Arizona, though.

[Aslkahuna]

the Equinox occurred on the 19th was in 2000 I believe and at the time Sky & Telescope noted that because of the Leap Year in 2000 we would see more of those occurrences since the purpose of the Leap Year protocol is to keep the Vernal Equinox date around the 20th and 21st of March. Most Calendars use EST as the time for determining the start of Spring and in this instance they were right as the Equinox occurred at 0649Z on the 20th which translates to 0149EST on the 20th or 2349MST on the 19th (which is why I phrased the message the way I did). I get my seasonal dates and times from S&T usually.

Steve