Rain, Rain, Go Away. April's Numbers in 'Twisted'

After a busy morning, I have run out of time to post. Remember you can track along on my Storm Page or TV Weather Graphics links above (on the full site). I will try to get back and post later. There is a cold front that could bring us showers Saturday night into Sunday- and yet another storm next week.
The official April Climate data is in as well. Who do you want to listen to, and what do you want to believe?

• From the National Climatic Data Center- For the contiguous United States, the average temperature for April was 51.0°F (10.6°C), which was 1.0°F (0.6°C) below the 20th century mean and ranked as the 29th coolest April on record, based on preliminary data.
  
• NOAA had this Headline: NOAA: U.S. Has Cool April, Global Temperature Ranked 13th Warmest on Record

• This is from Quark Soup- a blog my wife found: NASA GISS is out with their NASA GISS April '08 global land+ocean temperatures were +0.41°C above the long-term average. It has something for everyone: on the one hand, it's the coldest April in seven years. On the other hand, it's the 11th warmest April in GISS's recorded history (1990-2008).

I am glad I am not the only one not brainwashed by their skew. By the way, how long have we been tracking sea surface temperatures? I love that when it's cool- it's preliminary numbers. when it's about the heat- stop the press. I wonder what the carbon footprint is for using bold face font?
Just keep in mind, here in Baltimore we are running below normal in temperatures this month- including Monday's 50F high which was the coolest afternoon on record for the date. Including today's rain- we have about 2 inches left for the all time wettest May. We have a shot with 15 more days and a few more storms in the pipeline. I'll get into that this weekend.

It's Time To Complain- We're Going To Have More Rain

We already had 3 individual record rainfall days in the past week. Here is an updated map of the rainfall from the past two storms. I do not like to sensationalize the weather. Sure I love a good snow, almost look for it all winter... but I know the harm that is done when it is hyped too much. You as the public get frustrated and angry when the weather does not reach your expectations. That has been my philosophy with the Climate Debate, my forecasting on TV, and this blog. But here we go with more rain on the way.


This active storm track continues to reinforce itself. Call it atmospheric memory. We get locked into a pattern, and that is what we are in now. A pattern thanks to outside forces such as La Nina and the North Atlantic Oscillation (explained in previous posts). That is one of the reasons that Mother's Day forecast worked out as I tracked it from 6 days out. So here again is the Canadian Model outlook for Friday morning. I do suspect that this is a little fast, and the heavy rain will be in the afternoon. The gist is the Low and the position. Again just to our south in Virginia. That keeps us on the colder northern fringe, and more severe weather possible from VA Beach into the Carolinas.
For us- it's the potential for over 1 inch of rain that will build on the already swollen streams and saturated soil. Tomorrow I will post the record rain to see if we will be close, but it will make a dent in the monthly total. We have a good shot at that all time wettest May with half of the month and less than 3 inches to go. Another storm on this track is possible by Tuesday or Wednesday. If it's going to do it- we might as well have something to show for it.

A Record For Records. It's All In The Pattern

Yesterday's expectation proved true. Flooding rain and the bulls eye southern in AA County. Here is the NWS snapshot of rainfall just up through 8AM Monday- over 5 inches south of Annapolis. We hit the record for rainfall at 2.20". In fact, we hit the record 3 out of the last 4 days (Friday, Sunday and Monday). Another 2.63"and we will have the wettest May on record. More on that below. But as for the records, I did a little snooping, and discovered that there are quite a few times when two days in the same month and year hold the record rainfall. It reinforces the fact that extreme weather patterns can build on themselves. So potent storms can pair up and hold the test of time in the record books. While some records may have been eclipsed by later dates, here is a sample of the 'multiple' rainfall records currently on the books:
January-
1939 29th and 30th
1998 15th and 23rd

February-
1890 8th and 14th
1924 5th and 10th
1939 3rd and 28th
1998 4th and 23rd
2003 16th and 22nd
Wettest Jan and Feb in 1979
April
1910 17th and 24th
1924 6th and 18th

May
1909 21st and 27th
1921 4th and12th (broken 2008)
1976 1st and 29th
2008 9th, 11th, and 12th

As you can see, it's quite common and goes back over 100 years. Which is why I stopped at May, it would take a while... What is unique is the cluster and more so the 3 days in the same month/year we just had. It's all part of a pattern that is now taking the storm track over Maryland. I expect more in the next week or so. Here is why:

First the North Atlantic Oscillation (NAO). It is a blocking pattern that allows cold air to shift south from Canada into the Mid Atlantic and shift the storm track... In the winter it is promising for snow, but in the spring- just delayed a few months- it brings us frequent rain events, but shifts the severe weather threat from the central plains to the south east USA. When the index is negative, we have a block and the cool stormy pattern. here you can see that we made that shift in mid March- and have been there ever since. That was what I expected to give us a last snow, which did not happen. But my outlook was not entirely wrong. The red line at the end of the chart is the spaghetti plot or multiple model outlook for the end of May trending back to neutral or Zero. That follows a notion I mentioned recently... we can jump right into summer.
Before that happens, we have to consider what is left in this pattern. Here is the 500mb jet stream showing our current ridge, with clearing skies. The trough out west is the stormy pattern, along with a nearly closed Low moving through the desert southwest. This a cold pocket of unsettled air responsible for more snow in Arizona and Colorado today. The slant (up and right) indicates a progressive pattern, which means it is moving eastbound- but that block in the north Atlantic provides an atmospheric northerly flow, preventing that storm from passing to our west. Instead, it gets suppressed and travels almost due east. It should reach us by Thursday night and Friday. While not as impressive as the last storm, it should in it's own right bring a chilly wet Friday to us. Too early to say how much rain we could get, but any more at this point is too much. A guarantee though that more severe weather will develop in it's path in some of the same areas that were hit last weekend.