Oct 062014
 

The remnants of Hurricane Simon are on their way to Arizona. The big question is still around which path he will take. The Navy NoGAPs computer model has the bulk of the storm going to the west and north of Flagstaff. The GFS model has the storm going to the south and east of Flagstaff. Which way will he go?

You can see the subtle differences in the two models below. The National Weather Service’s chances of rain peak at 50% right. Wunderground peaks at 80%. Accuweather is forecasting rain and thunderstorms. I think we are going to get wet. I think we need to keep an eye on this storm because it can bring heavy rain and flooding…again.

6 hour precipitation outlook at 48 hours from the US Navy's NoGaps model.

6 hour precipitation outlook at 48 hours from the US Navy’s NoGAPs model.

6 hour precipitation outlook at 48 hours from the National Weather Service's GFS model.

6 hour precipitation outlook at 48 hours from the National Weather Service’s GFS model.

 Posted by at 5:27 pm
Sep 302014
 

I’ve struggled the last few days with a broken internet connection, malfunctioning iPhone and a rainy weekend. The weekend struggle was the wonderful malaise that can hit Arizonans when it rains all day. Nonetheless, the Climate Prediction Center issued new outlooks for October and the 3-month period October to December.

The outlooks point to El Nino developing. I’m still not sure this is a reasonable expectation. Last spring and early summer, the sea surface temperatures in the Pacific Ocean near the equator appeared headed for a strong El Nino. Unfortunately, the trade-winds did not shift to support it and the sea surface temperatures fell. There is another burst of warm water headed towards Peru now. If the winds shift, we will have El Nino conditions and a high likelihood of a wet winter. If they don’t shift, we will see La Nada neutral conditions(I think this is what will happen). Here is NOAA’s narrative about the outlooks:

CURRENT ATMOSPHERIC AND OCEANIC OBSERVATIONS ARE CONSISTENT WITH ENSO-NEUTRAL 
CONDITIONS WITH THE LIKELY TRANSITION TO EL NINO CONDITIONS IN AUTUMN AND 
WINTER. A WEAK EL NINO EVENT IS MOST PROBABLE, HOWEVER THERE IS A CHANCE OF 
EITHER A MODERATE EVENT OR CONTINUED ENSO-NEUTRAL CONDITIONS INTO WINTER. A 
STRONG EL NINO EVENT IS NOT LIKELY TO OCCUR THIS YEAR. MOST DYNAMICAL AND 
STATISTICAL MODEL FORECASTS OF EAST-CENTRAL EQUATORIAL PACIFIC SEA SURFACE 
TEMPERATURES (SSTS) IN THE NINO 3.4 REGION (170W TO 120W LONGITUDE AND 5S TO 5N 
LATITUDE) INDICATE A WEAK EL NINO (+0.5C TO +0.9C) WITH PEAK ANOMALIES IN THE 
EARLY WINTER.

 

Here are the outlooks:

One-month precipitation outlook for October 2014 from the Climate Prediction Center

One-month precipitation outlook for October 2014 from the Climate Prediction Center

Three-month precipitation outlook for October- December 2014  from the Climate Predicction Center.

Three-month precipitation outlook for October- December 2014 from the Climate Prediction Center.

 Posted by at 7:10 am
Sep 162014
 

I have zoomed in and cropped the image below. There is still a pronounced boundary to the heavy precipitation area. The precipitation scale is the same as in the earlier image in my last post. This is from a shorter range, high-resolution model. I think Flagstaff ends up in the 3/4 to 1 inch range. Notice that another boundary is forming along I-40 to the east. Stay tuned! There will be areas of Arizona receiving large amounts of precipitation over the next few days.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

 Posted by at 6:49 am
Sep 152014
 

Watching the GFS animation for the next 7 days this morning, I noticed a curious flow in the precipitation pattern. This flow reminded me of our last interaction with the remnants of a hurricane. Hurricane Norbert’s moisture missed us by traveling barely south of us. Next up for us are the remnants of Hurricane Odile. Currently, Odile is hitting Baja Mexico. Model predictions call for Odile’s moisture to move across most of Arizona. But, this morning’s GFS model for NOAA shows that a thin line might separate seriously wet areas from damp areas. We will have to keep watching to see where the water goes.

In the image below, I have added a yellow arrow to show the movement of precipitation. There is a large difference in the amounts to the southeast of the line and to the northwest of the line.

5-day total precipitation from the GFS model. Yellow arrow added for emphasis.

5-day total precipitation from the GFS model. Yellow arrow added for emphasis.

 Posted by at 6:34 am
Sep 052014
 

We will be entering another wet period this weekend. It will last through the first half of next week. The moisture is a result of an Eastern Pacific hurricane named Norbert. Norbert is tracking up the west coast of Baja Mexico. This morning, Norbert is west of the southern tip of the Baja Peninsula. Below is an animated GIF of the GFS Model for the next 4 days. It shows 24-hour predicted precipitation in daily intervals. You can see Norbert in the animation. He’s bringing plenty of moisture to Arizona.

Animation of 24-hour total precipitation, September 5-9, 2014. (GFS Model, NCEP Central Operations)

Animation of 24-hour total precipitation, September 5-9, 2014. (GFS Model, NCEP Central Operations)

 Posted by at 6:46 am
Aug 172014
 

In my last post, I pointed out that a drier period was ahead. What I had meant, and what the models foretold, was no rain for a week or so. That has not been the case. Thursday evening, a storm moved across the west side of Flagstaff dumping heavy rain across the area. Friday evening a storm hit central Flagstaff. I got about 1/3 of an inch of rain. I got more rain on Saturday, a mere 0.03 inches. This is drier than earlier in the week when I received over an inch.

This dry trend will continue for the next few days with a 30-60% chance of rain each day through Thursday. I think that in wet years, the forecast models run on the dry side, especially at long lead times. In dry years, they run on the wet side. The result is that more is on the way for this week.

 Posted by at 10:16 pm
Jul 182014
 

This morning the Climate Prediction Center issued a new 90-day precipitation outlook. All of Arizona is in the above average precipitation zone.

Three-month precipitation outlook from the Climate Prediction Center.

Three-month precipitation outlook from the Climate Prediction Center.

 Posted by at 7:14 am
Jul 152014
 

Looking out 2 weeks, you might think so. Today is the last day in the current forecasts and outlooks when Northern Arizona can strongly expect rain. The winds are going to shift back to a southwesterly origin and bring dry air. Below are the 6-10 and 8-14 day outlooks. The Climate Prediction Center issues new 30 and 90-day outlooks on Thursday.

As a side note, it looks more and more like El Nino is going to fail before it is up and running. I get in to that detail later. However, this probably isn’t the driver behind our monsoon season.

6-10 day precipitation outlook from the Climate Prediction Center. (14 July 2014)

6-10 day precipitation outlook from the Climate Prediction Center. (14 July 2014)

8-14 day precipitation outlook from the Climate Prediction Center. (14 July 2014)

8-14 day precipitation outlook from the Climate Prediction Center. (14 July 2014)

 Posted by at 6:33 am
Aug 242013
 

Ivo. Well, my iPad recognizes Ivo as a proper noun. Given the rain we expect Ivo to bring this weekend, I thought the name could be derived from some archaic rain god. Nope.

Meaning & History
Germanic name, originally a short form of names beginning with the Germanic element iv meaning "yew".
Alternative theories suggest that it may in fact be derived from a cognate Celtic element. 
This was the name of several saints (who are also commonly known as Saint Yves or Ives).

Anyway, the air is wet today. Moisture is already surging northward. The Valley of the Sun had heavy rains and lightning over night. It will be wetter tomorrow. It still looks like Tropical Storm Ivo will end our August drought.

Infrared satellite image from Saturday morning. National Weather Service.

Infrared satellite image from Saturday morning showing Tropical Storm Ivo off the tip of the Baja Peninsula. Tropical moisture is already surging up from the south from this storm. National Weather Service.

 Posted by at 8:25 am
Aug 192013
 

According to the long-range outlooks and GFS model,  an intense low pressure system(now identified as 94E) will move up the west coast of Mexico and bring plenty of moisture next Sunday and Monday. It’s still a long ways out, but the GFS model and the 6-10 day outlook predict above average precipitation. It has been consistent for several model runs.

6-10 day precipitation outlook from the Climate Prediction Center. Monday Afternoon, August 19, 2013

6-10 day precipitation outlook from the Climate Prediction Center. Monday Afternoon, August 19, 2013

The last GFS model had the bulk of the precipitation falling in western Arizona. It’s not a sure bet, yet.

 Posted by at 5:41 pm
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