April 2-16, 2005 Pattern Discussion

[donsutherland1]

Last week’s discussion raised a number of issues of what one might expect for the March 27-April 9, 2005 period.

• Overall, the next 10-14 days will likely see a transition toward springlike weather in the East. Precipitation will likely run above to much above normal given that the NAO and PNA should both be trending toward modestly positive levels.

Warming has been occurring in the East. In addition, next week’s anomalies will likely be even warmer than those during the March 27-April 1 period. Rainfall has been much above normal through April 1.

• March 27-28 should see a widespread, heavy rainfall in excess of 1”. April 2-3 could see additional rain along with the passage of a cold front.

Rainfall totals for the March 27-28 period came to:
Boston: 1.79” (March 28-29)
New York City: 3.02”
Washington, DC: 1.61”

According to the computer guidance, another substantial rainfall appeared highly likely for late April 1 into April 3.

• The March 30-April 1 period will likely see warmer than normal to much warmer than normal readings in the Mid-Atlantic and Northeast. The temperature will likely exceed 60° in New York City and perhaps even Boston on at least one day during this stretch.

The March 30-April 1 period saw temperatures generally run somewhat above normal. Anomalies came to –0.25° in Boston, +2.25° in NYC, and +1.25° in Washington, DC. Although Boston’s warmest day was 51° (March 29), New York City had a high temperature of 63° (March 30).

• Colder weather will likely give way to a shot of unseasonable warmth in the Great Lakes region and Midwest. On March 26, Chicago and Detroit could see a little wet snow. March 28-29 should mark the arrival of a brief period of unseasonably warm readings and it is possible that both Chicago and Detroit could see at least one 60° or warmer reading during the March 28-March 31 timeframe.

Unseasonably warm weather moved into this region. Detroit picked up a little snow ahead of the warmth (0.1” on 3/25 and Trace on 3/26). The March 28-31 period was exceptionally warm with Detroit averaging 8.3° above normal and Chicago averaging 10.8° above normal. Each city saw temperatures reach or exceed 60° on 3 days:

Chicago:
March 28: 60°
March 29: 71°
March 30: 77°

Detroit:
March 29: 63°
March 30: 67°
March 31: 61°

Rain moved into this region late on April 1 and with it came cooling temperatures.

• Warmer than normal readings are likely in the Central Plains during the March 28-31 timeframe. Readings could surge into the 70s in both Omaha and Kansas City. A cold front should bring cooler readings on April 1. However, the cooler readings will likely be short-lived.

This region averaged much warmer than normal. During the March 28-31 timeframe, Kansas City averaged 6.5° above normal and Omaha averaged 11.3° above normal. Both cities saw highs above 70° on two days.

Kansas City:
March 28: 71°
March 29: 77°

Omaha:
March 28: 77°
March 29: 79°

It was cooler on April 1, but computer modeling indicated another strong warming trend shortly thereafter.

• A cool period appears to be on tap in Seattle. The shift toward a wetter pattern should continue. The March 26-27 period could see moderate or even heavy rain. Amounts will likely exceed 0.50”. Additional rain could occur during the April 1-2 timeframe.

March 26-27 saw Seattle pick up 2.15” rainfall. In addition, during the March 26-31 period, the temperature averaged 0.6° below normal in Seattle. Some light rain fell in the March 31-April 1 timeframe.

• Even as the Pacific Northwest is cool, warmth is likely across California. Los Angeles could experience much above normal readings during the March 26-April 2 timeframe. Little or no rainfall is likely during that stretch.

Los Angeles saw somewhat above normal temperatures during the March 26-April 1 period (+1.5°). On April 1, the mercury soared to 83° in downtown Los Angeles. Total rainfall during the March 26-April 1 period came to 0.11”.

The April 2-16, 2005 Ideas:

Overall, the ideas from last week about the general transition toward a more springlike pattern have worked out very well. If one examines the GFS ensembles, there are growing hints that the NAO will indeed see a positive regime get established at some point during the first 10 days in April.

• For the Northeast, a major storm will likely bring a widespread 1.50” to 3.00” rainfall to the Mid-Atlantic and Northeastern states in the April 2-3 timeframe. Behind this storm readings should remain somewhat below normal on April 4. A warming trend will likely see temperatures reach the 60s on April 7 in NYC and perhaps better than 70° in Washington, DC. Another storm could bring significant rainfall to the region in the April 8-9 timeframe. Behind this storm will likely follow a shot of unseasonably cool air, though not extreme. After the next weekend, the April 11-16 period will likely see noticeably warmer readings with frequent readings in the 60s to perhaps 70° as far north as southern New England.

• After a wet and cool start to the weekend in such cities as Chicago and Detroit, moderation should set in. Readings will likely run much above normal April 5-6 timeframe. It would not be surprising if at least one of those days sees the temperature reach 70° in either Chicago or Detroit. A sharp cold front should move through the region around April 7-8 with some rain showers possibly ending as snow showers. After a cool weekend, warmth should return for the following week.

• The Central Plains will see moderating temperatures during the coming weekend. The April 3-5 period will likely be exceptionally warm. On at least one day, the mercury will probably reach or exceed 80° in Kansas City and Omaha. A storm could bring some rain around April 6 followed by a few cooler days. A fresh warming trend could commence during the following weekend or just before (April 8-10 timeframe).

• Seattle will likely see cool and often wet weather through April 5. The April 2-4 period could see a cumulative total of more than 1” of rain. Afterward, somewhat milder temperatures should prevail for a few days. However, by April 8-9, cooler air and more rain could move into the Pacific Northwest.

• The April 2-7 period will likely see temperatures run above to much above normal in Los Angeles. One 2 or more days, the temperature will likely reach 80° or higher. Through April 10, there should be little or no rainfall. The April 11-16 period could see readings closer to normal but perhaps a little warmer than normal.

El Niño Continues a Slow Fade:
Bolstering the idea that no La Niña is likely during the spring or summer months, the present weak El Niño continues a very slow fade. The past two weeks had seen Region 3.4 warm up. However, cool anomalies persisted in Region 1+2 and all regions except Region 3.4 saw some cooling relative to normal during the week of March 23.

Temperature Anomalies:

Region 1+2:
Week of March 16: -0.4°C
Week of March 23: -1.1°C

Region 3.4:
Week of March 16: +0.5°C
Week of March 23: +0.6°C

With the continuing slow fade in the El Niño, my earlier ideas concerning an active hurricane season continue to look good. Moreover, Dr. Gray’s newest numbers look reasonable from my perspective. Where I disagree somewhat with Dr. Gray’s new estimates is that I believe that 4 or 5 major hurricanes is probably more likely than 3. A more detailed hurricane discussion will be posted sometime later this month. For now, the global indices continue to evolve as I expect that they will, so my thinking on the upcoming hurricane season (an active one) remains unchanged.

NOTE: After April, this discussion will appear only in the U.S. Weather Watch Forum until next fall.